Royce  Reinger

Royce Reinger

1664264899

10 Popular Graphics Library for Rust

In today's post we will learn about 10 Popular Graphics Library for Rust.

What is a Graphic?

In general, the term graphic refers to a design or visual image displayed on a variety of surfaces, including canvas, paper, walls, signs, or a computer monitor. They are created for entertainment, branding, or providing information.

CG or computer graphics are any image media, usually movies and pictures that are created through the use of hardware and software. They are often referred to as computer-generated imagery; more commonly known as CGI. An example of a computer graphic is the picture shown on this page.

Graphic may also be used to describe a phrase, gesture, or image that is considered obscene or offensive.

Table of contents:

  • RazrFalcon/rustybuzz - An incremental harfbuzz port to Rust.
  • Redox-os/rusttype - A pure Rust alternative to libraries like FreeType.
  • Gfx-rs/gfx - A high-performance, bindless graphics API for Rust. 
  • Gfx-rs/wgpu - Native WebGPU implementation based on gfx-hal. 
  • Brendanzab/gl-rs - An OpenGL function pointer loader for Rust.
  • Glium/glium - Safe OpenGL wrapper for the Rust language. 
  • PistonDevelopers/glfw-rs - GLFW3 bindings and idiomatic wrapper for Rust.
  • FSchutt/printpdf - PDF writing library.
  • J-F-Liu/lopdf - PDF document manipulation.
  • Kaj/rust-pdf - Generating PDF files in pure Rust.

1 - RazrFalcon/rustybuzz:

An incremental harfbuzz port to Rust.

rustybuzz is a complete harfbuzz's shaping algorithm port to Rust.

Matches harfbuzz v2.7.1

Why?

Because you can add rustybuzz = "*" to your project and it just works. No need for a C++ compiler. No need to configure anything. No need to link to system libraries.

Conformance

rustybuzz passes 98% of harfbuzz tests (1764 to be more precise). So it's mostly identical, but there are still some tiny edge-cases which are not implemented yet or cannot be implemented at all.

Also, Apple layout is largely untested, because we cannot include Apple fonts for legal reasons. harfbuzz uses macOS CI instances to test it, which is extremely painful and we do not do this for now.

Major changes

  • Subsetting removed.
  • TrueType parsing is completely handled by the ttf-parser. And while the parsing algorithm is very different, it's not better or worse, just different.
  • Malformed fonts will cause an error. HarfBuzz uses fallback/dummy shaper in this case.
  • No font size property. Shaping is always using UnitsPerEm. You should scale the result manually.
  • Most of the TrueType and Unicode handling code was moved into separate crates.
  • rustybuzz doesn't interact with any system libraries and must produce exactly the same results on all OS'es and targets.
  • mort table is not supported, since it's deprecated by Apple.
  • No Arabic fallback shaper, since it requires subsetting.
  • No graphite library support.
  • No automated Apple layout testing for legal reasons. We just cannot include Apple fonts. harfbuzz avoids this by running such tests only on CI, which is far from ideal.

Lines of code

As mentioned above, rustybuzz has around 20 KLOC. But this is not strictly true, because there are a lot of auto-generated data tables.

You can find the "real" code size using:

tokei --exclude unicode_norm.rs --exclude complex/vowel_constraints.rs \
      --exclude '*_machine.rs' --exclude '*_table.rs' src

Which gives us around 13 KLOC, which is still a lot.

Future work

Since the port is finished, there is not much to do other than syncing it with a new harfbuzz releases. But there are still a lot of room for performance optimizations and refactoring.

Also, despite the fact that harfbuzz has a vast test suite, there are still a lot of things left to test.

Safety

The library is completely safe.

We do have one unsafe to cast between two POD structures, which is perfectly safe. But except that, there are no unsafe in this library and in most of its dependencies (excluding bytemuck).

View on Github

2 - Redox-os/rusttype:

A pure Rust alternative to libraries like FreeType.

The current capabilities of RustType:

  • Reading OpenType formatted fonts and font collections. This includes *.ttf as well as *.otf font files.
  • Retrieving glyph shapes and commonly used properties for a font and its glyphs.
  • Laying out glyphs horizontally using horizontal and vertical metrics, and glyph-pair-specific kerning.
  • Rasterising glyphs with sub-pixel positioning using an accurate analytical algorithm (not based on sampling).
  • Managing a font cache on the GPU with the gpu_cache module. This keeps recently used glyph renderings in a dynamic cache in GPU memory to minimise texture uploads per-frame. It also allows you keep the draw call count for text very low, as all glyphs are kept in one GPU texture.

Notable things that RustType does not support yet:

  • Font hinting.
  • Ligatures of any kind.
  • Some less common TrueType sub-formats.
  • Right-to-left and vertical text layout.

Testing & examples

Heavier examples, tests & benchmarks are in the ./dev directory. This avoids dev-dependency feature bleed.

Run all tests with cargo test --all --all-features.

Run examples with cargo run --example <NAME> -p dev

Getting Started

To hit the ground running with RustType, look at dev/examples/ascii.rs supplied with the crate. It demonstrates loading a font file, rasterising an arbitrary string, and displaying the result as ASCII art. If you prefer to just look at the documentation, the entry point for loading fonts is Font, from which you can access individual fonts, then their glyphs.

Future Plans

The initial motivation for the project was to provide easy-to-use font rendering for games. There are numerous avenues for improving RustType. Ideas:

  • Support for some common forms of ligatures.
  • And, eventually, support for embedded right-to-left Unicode text.

If you think you could help with achieving any of these goals, feel free to open a tracking issue for discussing them.

View on Github

3 - Gfx-rs/gfx:

A high-performance, bindless graphics API for Rust.

gfx-rs is a low-level, cross-platform graphics and compute abstraction library in Rust. It consists of the following components:

gfx-hal deprecation

As of the v0.9 release, gfx-hal is now in maintenance mode. gfx-hal development was mainly driven by wgpu, which has now switched to its own GPU abstraction called wgpu-hal. For this reason, gfx-hal development has switched to maintenance only, until the developers figure out the story for gfx-portability. Read more about the transition in #3768.

hal

  • gfx-hal which is gfx's hardware abstraction layer: a Vulkan-ic mostly unsafe API which translates to native graphics backends.
  • gfx-backend-* which contains graphics backends for various platforms:
  • gfx-warden which is a data-driven reference test framework, used to verify consistency across all graphics backends.

gfx-rs is hard to use, it's recommended for performance-sensitive libraries and engines. If that's not your domain, take a look at wgpu-rs for a safe and simple alternative.

Hardware Abstraction Layer

The Hardware Abstraction Layer (HAL), is a thin, low-level graphics and compute layer which translates API calls to various backends, which allows for cross-platform support. The API of this layer is based on the Vulkan API, adapted to be more Rust-friendly.

Hardware Abstraction Layer (HAL)

Currently HAL has backends for Vulkan, DirectX 12/11, Metal, and OpenGL/OpenGL ES/WebGL.

The HAL layer is consumed directly by user applications or libraries. HAL is also used in efforts such as gfx-portability.

See the Big Picture blog post for connections.

The old gfx crate (pre-ll)

This repository was originally home to the gfx crate, which is now deprecated. You can find the latest versions of the code for that crate in the pre-ll branch of this repository.

The master branch of this repository is now focused on developing gfx-hal and its associated backend and helper libraries, as described above. gfx-hal is a complete rewrite of gfx, but it is not necessarily the direct successor to gfx. Instead, it serves a different purpose than the original gfx crate, by being "lower level" than the original. Hence, the name of gfx-hal was originally ll, which stands for "lower level", and the original gfx is now referred to as pre-ll.

The spiritual successor to the original gfx is actually wgpu, which stands on a similar level of abstraction to the old gfx crate, but with a modernized API that is more fit for being used over Vulkan/DX12/Metal. If you want something similar to the old gfx crate that is being actively developed, wgpu is probably what you're looking for, rather than gfx-hal.

View on Github

4 - Gfx-rs/wgpu:

Native WebGPU implementation based on gfx-hal.

wgpu is a cross-platform, safe, pure-rust graphics api. It runs natively on Vulkan, Metal, D3D12, D3D11, and OpenGLES; and on top of WebGPU on wasm.

The api is based on the WebGPU standard. It serves as the core of the WebGPU integration in Firefox, Servo, and Deno.

MSRV policy

Minimum Supported Rust Version is 1.59. It is enforced on CI (in "/.github/workflows/ci.yml") with RUST_VERSION variable. This version can only be upgraded in breaking releases.

Getting Started

Rust

Rust examples can be found at wgpu/examples. You can run the examples with cargo run --example name. See the list of examples. For detailed instructions, look at our Get Started wiki.

If you are looking for a wgpu tutorial, look at the following:

C/C++

To use wgpu in C/C++, you need wgpu-native.

Others

If you want to use wgpu in other languages, there are many bindings to wgpu-native from languages such as Python, D, Julia, Kotlin, and more. See the list.

Core Test Infrastructure

We use a tool called cargo nextest to run our tests. To install it, run cargo install cargo-nextest.

To run the test suite on the default device:

cargo nextest run --no-fail-fast

wgpu-info can run the tests once for each adapter on your system.

cargo run --bin wgpu-info -- cargo nextest run --no-fail-fast

Then to run an example's image comparison tests, run:

cargo nextest run <example-test-name> --no-fail-fast

Or run a part of the integration test suite:

cargo nextest run -p wgpu -- <name-of-test>

If you are a user and want a way to help contribute to wgpu, we always need more help writing test cases.

WebGPU Conformance Test Suite

WebGPU includes a Conformance Test Suite to validate that implementations are working correctly. We can run this CTS against wgpu.

To run the CTS, first you need to check it out:

git clone https://github.com/gpuweb/cts.git
cd cts
# works in bash and powershell
git checkout $(cat ../cts_runner/revision.txt)

To run a given set of tests:

# Must be inside the cts folder we just checked out, else this will fail
cargo run --manifest-path ../cts_runner/Cargo.toml -- ./tools/run_deno --verbose "<test string>"

To find the full list of tests, go to the online cts viewer.

The list of currently enabled CTS tests can be found here.

View on Github

5 - Brendanzab/gl-rs:

An OpenGL function pointer loader for Rust.

Overview

This repository contains the necessary building blocks for OpenGL wrapper libraries. For more information on each crate, see their respective READMEs listed below.

The following crates are contained in this repository:

gl

README

An OpenGL function pointer loader for the Rust Programming Language.

[dependencies]
gl = "0.14.0"

gl_generator

README

Code generators for creating bindings to the Khronos OpenGL APIs.

[build-dependencies]
gl_generator = "0.14.0"

khronos_api

README

The Khronos XML API Registry, exposed as byte string constants.

[build-dependencies]
khronos_api = "3.1.0"

Compiling from source

khronos_api makes use of git submodules. You will need to initialize these before building:

git submodule update --init

webgl_generator

README

Code generators for creating bindings to the WebGL APIs.

[build-dependencies]
webgl_generator = "0.2.0"

View on Github

6 - Glium/glium:

Safe OpenGL wrapper for the Rust language.

Note to current and future Glium users:

Glium is no longer actively developed by its original author. That said, PRs are still welcome and maintenance is continued by the surrounding community.

Elegant and safe OpenGL wrapper.

Glium is an intermediate layer between OpenGL and your application. You still need to manually handle the graphics pipeline, but without having to use OpenGL's old and error-prone API.

[dependencies] glium = "*"

Its objectives:

  • Be safe to use. Many aspects of OpenGL that can trigger a crash if misused are automatically handled by glium.
  • Provide an API that enforces good practices such as RAII or stateless function calls.
  • Be compatible with all OpenGL versions that support shaders, providing a unified API when things diverge.
  • Avoid all OpenGL errors beforehand.
  • Produce optimized OpenGL function calls, and allow the user to easily use modern OpenGL techniques.

Why should I use Glium instead of raw OpenGL calls?

Easy to use:

Functions are higher level in glium than in OpenGL. Glium's API tries to be as Rusty as possible, and shouldn't be much different than using any other Rust library. Glium should allow you to do everything that OpenGL allows you to do, just through high-level functions. If something is missing, please open an issue.

You can directly pass vectors, matrices and images to glium instead of manipulating low-level data.

Thanks to glutin, glium is very easy to setup compared to raw OpenGL.

Glium provides easier ways to do common tasks. For example the VertexBuffer struct contains information about the vertex bindings, because you usually don't use several different bindings with the same vertex buffer. This reduces the overall complexity of OpenGL.

Glium handles framebuffer objects, samplers, and vertex array objects for you. You no longer need to create them explicitly as they are automatically created when needed and destroyed when their corresponding object is destroyed.

Glium is stateless. There are no set_something() functions in the entire library, and everything is done by parameter passing. The same set of function calls will always produce the same results, which greatly reduces the number of potential problems.

Safety:

Glium detects what would normally be errors or undefined behaviors in OpenGL, and panics, without calling glGetError which would be too slow. Examples include requesting a depth test when you don't have a depth buffer available, not binding any value to an attribute or uniform, or binding multiple textures with different dimensions to the same framebuffer.

If the OpenGL context triggers an error, then you have found a bug in glium. Please open an issue. Just like Rust does everything it can to avoid crashes, glium does everything it can to avoid OpenGL errors.

The OpenGL context is automatically handled by glium. You don't need to worry about thread safety, as it is forbidden to change the thread in which OpenGL objects operate. Glium also allows you to safely replace the current OpenGL context with another one that shares the same lists.

Glium enforces RAII. Creating a Texture2d struct creates a texture, and destroying the struct destroys the texture. It also uses Rust's borrow system to ensure that objects are still alive and in the right state when you use them. Glium provides the same guarantees with OpenGL objects that you have with regular objects in Rust.

High-level functions are much easier to use and thus less error-prone. For example there is no risk of making a mistake while specifying the names and offsets of your vertex attributes, since Glium automatically generates this data for you.

Robustness is automatically handled. If the OpenGL context is lost (because of a crash in the driver for example) then swapping buffers will return an error.

View on Github

7 - PistonDevelopers/glfw-rs:

GLFW3 bindings and idiomatic wrapper for Rust.

Example

extern crate glfw;

use glfw::{Action, Context, Key};

fn main() {
    let mut glfw = glfw::init(glfw::FAIL_ON_ERRORS).unwrap();

    let (mut window, events) = glfw.create_window(300, 300, "Hello this is window", glfw::WindowMode::Windowed)
        .expect("Failed to create GLFW window.");

    window.set_key_polling(true);
    window.make_current();

    while !window.should_close() {
        glfw.poll_events();
        for (_, event) in glfw::flush_messages(&events) {
            handle_window_event(&mut window, event);
        }
    }
}

fn handle_window_event(window: &mut glfw::Window, event: glfw::WindowEvent) {
    match event {
        glfw::WindowEvent::Key(Key::Escape, _, Action::Press, _) => {
            window.set_should_close(true)
        }
        _ => {}
    }
}

Using glfw-rs

Prerequisites

Make sure you have compiled and installed GLFW 3.x. You might be able to find it on your package manager, for example on OS X: brew install glfw3 (you may need to run brew tap homebrew/versions). If not you can download and build the library from the source supplied on the GLFW website. Note that if you compile GLFW with CMake on Linux, you will have to supply the -DCMAKE_C_FLAGS=-fPIC argument. You may install GLFW to your PATH, otherwise you will have to specify the directory containing the library binaries when you call make or make lib:

GLFW_LIB_DIR=path/to/glfw/lib/directory make

Including glfw-rs in your project

Add this to your Cargo.toml:

[dependencies.glfw]
git = "https://github.com/bjz/glfw-rs.git"

On Windows

By default, glfw-rs will try to compile the glfw library. If you want to link to your custom build of glfw or if the build doesn't work (which is probably the case on Windows), you can disable this:

[dependencies.glfw]
git = "https://github.com/bjz/glfw-rs.git"
default-features = false

View on Github

8 - FSchutt/printpdf:

PDF writing library.

printpdf is a library designed for creating printable PDF documents.

[dependencies]
printpdf = "0.5.0"

Features

Currently, printpdf can only write documents, not read them.

  • Page generation
  • Layers (Illustrator like layers)
  • Graphics (lines, shapes, bezier curves)
  • Images (currently BMP/PNG/JPG only or generate your own images)
  • Embedded fonts (TTF and OTF) with Unicode support
  • Advanced graphics - overprint control, blending modes, etc.
  • Advanced typography - character scaling, character spacing, superscript, subscript, outlining, etc.
  • PDF layers (you should be able to open the PDF in Illustrator and have the layers appear)

Getting started

Writing PDF

Simple page

use printpdf::*;
use std::fs::File;
use std::io::BufWriter;

let (doc, page1, layer1) = PdfDocument::new("PDF_Document_title", Mm(247.0), Mm(210.0), "Layer 1");
let (page2, layer1) = doc.add_page(Mm(10.0), Mm(250.0),"Page 2, Layer 1");

doc.save(&mut BufWriter::new(File::create("test_working.pdf").unwrap())).unwrap();

Adding graphical shapes

use printpdf::*;
use std::fs::File;
use std::io::BufWriter;
use std::iter::FromIterator;

let (doc, page1, layer1) = PdfDocument::new("printpdf graphics test", Mm(297.0), Mm(210.0), "Layer 1");
let current_layer = doc.get_page(page1).get_layer(layer1);

// Quadratic shape. The "false" determines if the next (following)
// point is a bezier handle (for curves)
// If you want holes, simply reorder the winding of the points to be
// counterclockwise instead of clockwise.
let points1 = vec![(Point::new(Mm(100.0), Mm(100.0)), false),
                   (Point::new(Mm(100.0), Mm(200.0)), false),
                   (Point::new(Mm(300.0), Mm(200.0)), false),
                   (Point::new(Mm(300.0), Mm(100.0)), false)];

// Is the shape stroked? Is the shape closed? Is the shape filled?
let line1 = Line {
    points: points1,
    is_closed: true,
    has_fill: true,
    has_stroke: true,
    is_clipping_path: false,
};

// Triangle shape
// Note: Line is invisible by default, the previous method of
// constructing a line is recommended!
let mut line2 = Line::from_iter(vec![
    (Point::new(Mm(150.0), Mm(150.0)), false),
    (Point::new(Mm(150.0), Mm(250.0)), false),
    (Point::new(Mm(350.0), Mm(250.0)), false)]);

line2.set_stroke(true);
line2.set_closed(false);
line2.set_fill(false);
line2.set_as_clipping_path(false);

let fill_color = Color::Cmyk(Cmyk::new(0.0, 0.23, 0.0, 0.0, None));
let outline_color = Color::Rgb(Rgb::new(0.75, 1.0, 0.64, None));
let mut dash_pattern = LineDashPattern::default();
dash_pattern.dash_1 = Some(20);

current_layer.set_fill_color(fill_color);
current_layer.set_outline_color(outline_color);
current_layer.set_outline_thickness(10.0);

// Draw first line
current_layer.add_shape(line1);

let fill_color_2 = Color::Cmyk(Cmyk::new(0.0, 0.0, 0.0, 0.0, None));
let outline_color_2 = Color::Greyscale(Greyscale::new(0.45, None));

// More advanced graphical options
current_layer.set_overprint_stroke(true);
current_layer.set_blend_mode(BlendMode::Seperable(SeperableBlendMode::Multiply));
current_layer.set_line_dash_pattern(dash_pattern);
current_layer.set_line_cap_style(LineCapStyle::Round);

current_layer.set_fill_color(fill_color_2);
current_layer.set_outline_color(outline_color_2);
current_layer.set_outline_thickness(15.0);

// draw second line
current_layer.add_shape(line2);

View on Github

9 - J-F-Liu/lopdf:

PDF document manipulation.

Example Code

  • Create PDF document
use lopdf::dictionary;
use lopdf::{Document, Object, Stream};
use lopdf::content::{Content, Operation};

let mut doc = Document::with_version("1.5");
let pages_id = doc.new_object_id();
let font_id = doc.add_object(dictionary! {
    "Type" => "Font",
    "Subtype" => "Type1",
    "BaseFont" => "Courier",
});
let resources_id = doc.add_object(dictionary! {
    "Font" => dictionary! {
        "F1" => font_id,
    },
});
let content = Content {
    operations: vec![
        Operation::new("BT", vec![]),
        Operation::new("Tf", vec!["F1".into(), 48.into()]),
        Operation::new("Td", vec![100.into(), 600.into()]),
        Operation::new("Tj", vec![Object::string_literal("Hello World!")]),
        Operation::new("ET", vec![]),
    ],
};
let content_id = doc.add_object(Stream::new(dictionary! {}, content.encode().unwrap()));
let page_id = doc.add_object(dictionary! {
    "Type" => "Page",
    "Parent" => pages_id,
    "Contents" => content_id,
});
let pages = dictionary! {
    "Type" => "Pages",
    "Kids" => vec![page_id.into()],
    "Count" => 1,
    "Resources" => resources_id,
    "MediaBox" => vec![0.into(), 0.into(), 595.into(), 842.into()],
};
doc.objects.insert(pages_id, Object::Dictionary(pages));
let catalog_id = doc.add_object(dictionary! {
    "Type" => "Catalog",
    "Pages" => pages_id,
});
doc.trailer.set("Root", catalog_id);
doc.compress();

// Store file in current working directory.
// Note: Line is exclude for when running tests
if false {
    doc.save("example.pdf").unwrap();
}
  • Merge PDF documents
use lopdf::dictionary;

use std::collections::BTreeMap;

use lopdf::content::{Content, Operation};
use lopdf::{Document, Object, ObjectId, Stream, Bookmark};

pub fn generate_fake_document() -> Document {
    let mut doc = Document::with_version("1.5");
    let pages_id = doc.new_object_id();
    let font_id = doc.add_object(dictionary! {
        "Type" => "Font",
        "Subtype" => "Type1",
        "BaseFont" => "Courier",
    });
    let resources_id = doc.add_object(dictionary! {
        "Font" => dictionary! {
            "F1" => font_id,
        },
    });
    let content = Content {
        operations: vec![
            Operation::new("BT", vec![]),
            Operation::new("Tf", vec!["F1".into(), 48.into()]),
            Operation::new("Td", vec![100.into(), 600.into()]),
            Operation::new("Tj", vec![Object::string_literal("Hello World!")]),
            Operation::new("ET", vec![]),
        ],
    };
    let content_id = doc.add_object(Stream::new(dictionary! {}, content.encode().unwrap()));
    let page_id = doc.add_object(dictionary! {
        "Type" => "Page",
        "Parent" => pages_id,
        "Contents" => content_id,
        "Resources" => resources_id,
        "MediaBox" => vec![0.into(), 0.into(), 595.into(), 842.into()],
    });
    let pages = dictionary! {
        "Type" => "Pages",
        "Kids" => vec![page_id.into()],
        "Count" => 1,
    };
    doc.objects.insert(pages_id, Object::Dictionary(pages));
    let catalog_id = doc.add_object(dictionary! {
        "Type" => "Catalog",
        "Pages" => pages_id,
    });
    doc.trailer.set("Root", catalog_id);

    doc
}

fn main() -> std::io::Result<()> {
    // Generate a stack of Documents to merge
    let documents = vec![
        generate_fake_document(),
        generate_fake_document(),
        generate_fake_document(),
        generate_fake_document(),
    ];

    // Define a starting max_id (will be used as start index for object_ids)
    let mut max_id = 1;
    let mut pagenum = 1;
    // Collect all Documents Objects grouped by a map
    let mut documents_pages = BTreeMap::new();
    let mut documents_objects = BTreeMap::new();
    let mut document = Document::with_version("1.5");

    for mut doc in documents {
        let mut first = false;
        doc.renumber_objects_with(max_id);

        max_id = doc.max_id + 1;

        documents_pages.extend(
            doc
                    .get_pages()
                    .into_iter()
                    .map(|(_, object_id)| {
                        if !first {
                            let bookmark = Bookmark::new(String::from(format!("Page_{}", pagenum)), [0.0, 0.0, 1.0], 0, object_id);
                            document.add_bookmark(bookmark, None);
                            first = true;
                            pagenum += 1;
                        }

                        (
                            object_id,
                            doc.get_object(object_id).unwrap().to_owned(),
                        )
                    })
                    .collect::<BTreeMap<ObjectId, Object>>(),
        );
        documents_objects.extend(doc.objects);
    }

    // Catalog and Pages are mandatory
    let mut catalog_object: Option<(ObjectId, Object)> = None;
    let mut pages_object: Option<(ObjectId, Object)> = None;

    // Process all objects except "Page" type
    for (object_id, object) in documents_objects.iter() {
        // We have to ignore "Page" (as are processed later), "Outlines" and "Outline" objects
        // All other objects should be collected and inserted into the main Document
        match object.type_name().unwrap_or("") {
            "Catalog" => {
                // Collect a first "Catalog" object and use it for the future "Pages"
                catalog_object = Some((
                    if let Some((id, _)) = catalog_object {
                        id
                    } else {
                        *object_id
                    },
                    object.clone(),
                ));
            }
            "Pages" => {
                // Collect and update a first "Pages" object and use it for the future "Catalog"
                // We have also to merge all dictionaries of the old and the new "Pages" object
                if let Ok(dictionary) = object.as_dict() {
                    let mut dictionary = dictionary.clone();
                    if let Some((_, ref object)) = pages_object {
                        if let Ok(old_dictionary) = object.as_dict() {
                            dictionary.extend(old_dictionary);
                        }
                    }

                    pages_object = Some((
                        if let Some((id, _)) = pages_object {
                            id
                        } else {
                            *object_id
                        },
                        Object::Dictionary(dictionary),
                    ));
                }
            }
            "Page" => {}     // Ignored, processed later and separately
            "Outlines" => {} // Ignored, not supported yet
            "Outline" => {}  // Ignored, not supported yet
            _ => {
                document.objects.insert(*object_id, object.clone());
            }
        }
    }

    // If no "Pages" found abort
    if pages_object.is_none() {
        println!("Pages root not found.");

        return Ok(());
    }

    // Iter over all "Page" and collect with the parent "Pages" created before
    for (object_id, object) in documents_pages.iter() {
        if let Ok(dictionary) = object.as_dict() {
            let mut dictionary = dictionary.clone();
            dictionary.set("Parent", pages_object.as_ref().unwrap().0);

            document
                    .objects
                    .insert(*object_id, Object::Dictionary(dictionary));
        }
    }

    // If no "Catalog" found abort
    if catalog_object.is_none() {
        println!("Catalog root not found.");

        return Ok(());
    }

    let catalog_object = catalog_object.unwrap();
    let pages_object = pages_object.unwrap();

    // Build a new "Pages" with updated fields
    if let Ok(dictionary) = pages_object.1.as_dict() {
        let mut dictionary = dictionary.clone();

        // Set new pages count
        dictionary.set("Count", documents_pages.len() as u32);

        // Set new "Kids" list (collected from documents pages) for "Pages"
        dictionary.set(
            "Kids",
            documents_pages
                    .into_iter()
                    .map(|(object_id, _)| Object::Reference(object_id))
                    .collect::<Vec<_>>(),
        );

        document
                .objects
                .insert(pages_object.0, Object::Dictionary(dictionary));
    }

    // Build a new "Catalog" with updated fields
    if let Ok(dictionary) = catalog_object.1.as_dict() {
        let mut dictionary = dictionary.clone();
        dictionary.set("Pages", pages_object.0);
        dictionary.remove(b"Outlines"); // Outlines not supported in merged PDFs

        document
                .objects
                .insert(catalog_object.0, Object::Dictionary(dictionary));
    }

    document.trailer.set("Root", catalog_object.0);

    // Update the max internal ID as wasn't updated before due to direct objects insertion
    document.max_id = document.objects.len() as u32;

    // Reorder all new Document objects
    document.renumber_objects();

     //Set any Bookmarks to the First child if they are not set to a page
    document.adjust_zero_pages();

    //Set all bookmarks to the PDF Object tree then set the Outlines to the Bookmark content map.
    if let Some(n) = document.build_outline() {
        if let Ok(x) = document.get_object_mut(catalog_object.0) {
            if let Object::Dictionary(ref mut dict) = x {
                dict.set("Outlines", Object::Reference(n));
            }
        }
    }

    document.compress();

    // Save the merged PDF
    // Store file in current working directory.
    // Note: Line is exclude for when running tests
    if false {
        document.save("merged.pdf").unwrap();
    }

    Ok(())
}

View on Github

10 - Kaj/rust-pdf:

Generating PDF files in pure Rust.

A pure rust library for generating PDF files. Currently, simple vector graphics and text set in the 14 built-in fonts are supported.  

To use this library, add it as a dependency in your Cargo.toml:

[dependencies]
pdf-canvas = "*"

The API is still very alpha, usage may change. Some examples, that should work with the version containing them, can be found in the examples directory. Read the API documentation for the pdf-canvas crate. A larger example of a program using this crate is chord3, a chopro formatter.

View on Github

Thank you for following this article.

Related videos:

Intro to Rust-lang (Games and Graphics with Piston; Pong game)

#rust #graphic 

What is GEEK

Buddha Community

10 Popular Graphics Library for Rust

Serde Rust: Serialization Framework for Rust

Serde

*Serde is a framework for serializing and deserializing Rust data structures efficiently and generically.*

You may be looking for:

Serde in action

Click to show Cargo.toml. Run this code in the playground.

[dependencies]

# The core APIs, including the Serialize and Deserialize traits. Always
# required when using Serde. The "derive" feature is only required when
# using #[derive(Serialize, Deserialize)] to make Serde work with structs
# and enums defined in your crate.
serde = { version = "1.0", features = ["derive"] }

# Each data format lives in its own crate; the sample code below uses JSON
# but you may be using a different one.
serde_json = "1.0"

 

use serde::{Serialize, Deserialize};

#[derive(Serialize, Deserialize, Debug)]
struct Point {
    x: i32,
    y: i32,
}

fn main() {
    let point = Point { x: 1, y: 2 };

    // Convert the Point to a JSON string.
    let serialized = serde_json::to_string(&point).unwrap();

    // Prints serialized = {"x":1,"y":2}
    println!("serialized = {}", serialized);

    // Convert the JSON string back to a Point.
    let deserialized: Point = serde_json::from_str(&serialized).unwrap();

    // Prints deserialized = Point { x: 1, y: 2 }
    println!("deserialized = {:?}", deserialized);
}

Getting help

Serde is one of the most widely used Rust libraries so any place that Rustaceans congregate will be able to help you out. For chat, consider trying the #rust-questions or #rust-beginners channels of the unofficial community Discord (invite: https://discord.gg/rust-lang-community), the #rust-usage or #beginners channels of the official Rust Project Discord (invite: https://discord.gg/rust-lang), or the #general stream in Zulip. For asynchronous, consider the [rust] tag on StackOverflow, the /r/rust subreddit which has a pinned weekly easy questions post, or the Rust Discourse forum. It's acceptable to file a support issue in this repo but they tend not to get as many eyes as any of the above and may get closed without a response after some time.

Download Details:
Author: serde-rs
Source Code: https://github.com/serde-rs/serde
License: View license

#rust  #rustlang 

Royce  Reinger

Royce Reinger

1664264899

10 Popular Graphics Library for Rust

In today's post we will learn about 10 Popular Graphics Library for Rust.

What is a Graphic?

In general, the term graphic refers to a design or visual image displayed on a variety of surfaces, including canvas, paper, walls, signs, or a computer monitor. They are created for entertainment, branding, or providing information.

CG or computer graphics are any image media, usually movies and pictures that are created through the use of hardware and software. They are often referred to as computer-generated imagery; more commonly known as CGI. An example of a computer graphic is the picture shown on this page.

Graphic may also be used to describe a phrase, gesture, or image that is considered obscene or offensive.

Table of contents:

  • RazrFalcon/rustybuzz - An incremental harfbuzz port to Rust.
  • Redox-os/rusttype - A pure Rust alternative to libraries like FreeType.
  • Gfx-rs/gfx - A high-performance, bindless graphics API for Rust. 
  • Gfx-rs/wgpu - Native WebGPU implementation based on gfx-hal. 
  • Brendanzab/gl-rs - An OpenGL function pointer loader for Rust.
  • Glium/glium - Safe OpenGL wrapper for the Rust language. 
  • PistonDevelopers/glfw-rs - GLFW3 bindings and idiomatic wrapper for Rust.
  • FSchutt/printpdf - PDF writing library.
  • J-F-Liu/lopdf - PDF document manipulation.
  • Kaj/rust-pdf - Generating PDF files in pure Rust.

1 - RazrFalcon/rustybuzz:

An incremental harfbuzz port to Rust.

rustybuzz is a complete harfbuzz's shaping algorithm port to Rust.

Matches harfbuzz v2.7.1

Why?

Because you can add rustybuzz = "*" to your project and it just works. No need for a C++ compiler. No need to configure anything. No need to link to system libraries.

Conformance

rustybuzz passes 98% of harfbuzz tests (1764 to be more precise). So it's mostly identical, but there are still some tiny edge-cases which are not implemented yet or cannot be implemented at all.

Also, Apple layout is largely untested, because we cannot include Apple fonts for legal reasons. harfbuzz uses macOS CI instances to test it, which is extremely painful and we do not do this for now.

Major changes

  • Subsetting removed.
  • TrueType parsing is completely handled by the ttf-parser. And while the parsing algorithm is very different, it's not better or worse, just different.
  • Malformed fonts will cause an error. HarfBuzz uses fallback/dummy shaper in this case.
  • No font size property. Shaping is always using UnitsPerEm. You should scale the result manually.
  • Most of the TrueType and Unicode handling code was moved into separate crates.
  • rustybuzz doesn't interact with any system libraries and must produce exactly the same results on all OS'es and targets.
  • mort table is not supported, since it's deprecated by Apple.
  • No Arabic fallback shaper, since it requires subsetting.
  • No graphite library support.
  • No automated Apple layout testing for legal reasons. We just cannot include Apple fonts. harfbuzz avoids this by running such tests only on CI, which is far from ideal.

Lines of code

As mentioned above, rustybuzz has around 20 KLOC. But this is not strictly true, because there are a lot of auto-generated data tables.

You can find the "real" code size using:

tokei --exclude unicode_norm.rs --exclude complex/vowel_constraints.rs \
      --exclude '*_machine.rs' --exclude '*_table.rs' src

Which gives us around 13 KLOC, which is still a lot.

Future work

Since the port is finished, there is not much to do other than syncing it with a new harfbuzz releases. But there are still a lot of room for performance optimizations and refactoring.

Also, despite the fact that harfbuzz has a vast test suite, there are still a lot of things left to test.

Safety

The library is completely safe.

We do have one unsafe to cast between two POD structures, which is perfectly safe. But except that, there are no unsafe in this library and in most of its dependencies (excluding bytemuck).

View on Github

2 - Redox-os/rusttype:

A pure Rust alternative to libraries like FreeType.

The current capabilities of RustType:

  • Reading OpenType formatted fonts and font collections. This includes *.ttf as well as *.otf font files.
  • Retrieving glyph shapes and commonly used properties for a font and its glyphs.
  • Laying out glyphs horizontally using horizontal and vertical metrics, and glyph-pair-specific kerning.
  • Rasterising glyphs with sub-pixel positioning using an accurate analytical algorithm (not based on sampling).
  • Managing a font cache on the GPU with the gpu_cache module. This keeps recently used glyph renderings in a dynamic cache in GPU memory to minimise texture uploads per-frame. It also allows you keep the draw call count for text very low, as all glyphs are kept in one GPU texture.

Notable things that RustType does not support yet:

  • Font hinting.
  • Ligatures of any kind.
  • Some less common TrueType sub-formats.
  • Right-to-left and vertical text layout.

Testing & examples

Heavier examples, tests & benchmarks are in the ./dev directory. This avoids dev-dependency feature bleed.

Run all tests with cargo test --all --all-features.

Run examples with cargo run --example <NAME> -p dev

Getting Started

To hit the ground running with RustType, look at dev/examples/ascii.rs supplied with the crate. It demonstrates loading a font file, rasterising an arbitrary string, and displaying the result as ASCII art. If you prefer to just look at the documentation, the entry point for loading fonts is Font, from which you can access individual fonts, then their glyphs.

Future Plans

The initial motivation for the project was to provide easy-to-use font rendering for games. There are numerous avenues for improving RustType. Ideas:

  • Support for some common forms of ligatures.
  • And, eventually, support for embedded right-to-left Unicode text.

If you think you could help with achieving any of these goals, feel free to open a tracking issue for discussing them.

View on Github

3 - Gfx-rs/gfx:

A high-performance, bindless graphics API for Rust.

gfx-rs is a low-level, cross-platform graphics and compute abstraction library in Rust. It consists of the following components:

gfx-hal deprecation

As of the v0.9 release, gfx-hal is now in maintenance mode. gfx-hal development was mainly driven by wgpu, which has now switched to its own GPU abstraction called wgpu-hal. For this reason, gfx-hal development has switched to maintenance only, until the developers figure out the story for gfx-portability. Read more about the transition in #3768.

hal

  • gfx-hal which is gfx's hardware abstraction layer: a Vulkan-ic mostly unsafe API which translates to native graphics backends.
  • gfx-backend-* which contains graphics backends for various platforms:
  • gfx-warden which is a data-driven reference test framework, used to verify consistency across all graphics backends.

gfx-rs is hard to use, it's recommended for performance-sensitive libraries and engines. If that's not your domain, take a look at wgpu-rs for a safe and simple alternative.

Hardware Abstraction Layer

The Hardware Abstraction Layer (HAL), is a thin, low-level graphics and compute layer which translates API calls to various backends, which allows for cross-platform support. The API of this layer is based on the Vulkan API, adapted to be more Rust-friendly.

Hardware Abstraction Layer (HAL)

Currently HAL has backends for Vulkan, DirectX 12/11, Metal, and OpenGL/OpenGL ES/WebGL.

The HAL layer is consumed directly by user applications or libraries. HAL is also used in efforts such as gfx-portability.

See the Big Picture blog post for connections.

The old gfx crate (pre-ll)

This repository was originally home to the gfx crate, which is now deprecated. You can find the latest versions of the code for that crate in the pre-ll branch of this repository.

The master branch of this repository is now focused on developing gfx-hal and its associated backend and helper libraries, as described above. gfx-hal is a complete rewrite of gfx, but it is not necessarily the direct successor to gfx. Instead, it serves a different purpose than the original gfx crate, by being "lower level" than the original. Hence, the name of gfx-hal was originally ll, which stands for "lower level", and the original gfx is now referred to as pre-ll.

The spiritual successor to the original gfx is actually wgpu, which stands on a similar level of abstraction to the old gfx crate, but with a modernized API that is more fit for being used over Vulkan/DX12/Metal. If you want something similar to the old gfx crate that is being actively developed, wgpu is probably what you're looking for, rather than gfx-hal.

View on Github

4 - Gfx-rs/wgpu:

Native WebGPU implementation based on gfx-hal.

wgpu is a cross-platform, safe, pure-rust graphics api. It runs natively on Vulkan, Metal, D3D12, D3D11, and OpenGLES; and on top of WebGPU on wasm.

The api is based on the WebGPU standard. It serves as the core of the WebGPU integration in Firefox, Servo, and Deno.

MSRV policy

Minimum Supported Rust Version is 1.59. It is enforced on CI (in "/.github/workflows/ci.yml") with RUST_VERSION variable. This version can only be upgraded in breaking releases.

Getting Started

Rust

Rust examples can be found at wgpu/examples. You can run the examples with cargo run --example name. See the list of examples. For detailed instructions, look at our Get Started wiki.

If you are looking for a wgpu tutorial, look at the following:

C/C++

To use wgpu in C/C++, you need wgpu-native.

Others

If you want to use wgpu in other languages, there are many bindings to wgpu-native from languages such as Python, D, Julia, Kotlin, and more. See the list.

Core Test Infrastructure

We use a tool called cargo nextest to run our tests. To install it, run cargo install cargo-nextest.

To run the test suite on the default device:

cargo nextest run --no-fail-fast

wgpu-info can run the tests once for each adapter on your system.

cargo run --bin wgpu-info -- cargo nextest run --no-fail-fast

Then to run an example's image comparison tests, run:

cargo nextest run <example-test-name> --no-fail-fast

Or run a part of the integration test suite:

cargo nextest run -p wgpu -- <name-of-test>

If you are a user and want a way to help contribute to wgpu, we always need more help writing test cases.

WebGPU Conformance Test Suite

WebGPU includes a Conformance Test Suite to validate that implementations are working correctly. We can run this CTS against wgpu.

To run the CTS, first you need to check it out:

git clone https://github.com/gpuweb/cts.git
cd cts
# works in bash and powershell
git checkout $(cat ../cts_runner/revision.txt)

To run a given set of tests:

# Must be inside the cts folder we just checked out, else this will fail
cargo run --manifest-path ../cts_runner/Cargo.toml -- ./tools/run_deno --verbose "<test string>"

To find the full list of tests, go to the online cts viewer.

The list of currently enabled CTS tests can be found here.

View on Github

5 - Brendanzab/gl-rs:

An OpenGL function pointer loader for Rust.

Overview

This repository contains the necessary building blocks for OpenGL wrapper libraries. For more information on each crate, see their respective READMEs listed below.

The following crates are contained in this repository:

gl

README

An OpenGL function pointer loader for the Rust Programming Language.

[dependencies]
gl = "0.14.0"

gl_generator

README

Code generators for creating bindings to the Khronos OpenGL APIs.

[build-dependencies]
gl_generator = "0.14.0"

khronos_api

README

The Khronos XML API Registry, exposed as byte string constants.

[build-dependencies]
khronos_api = "3.1.0"

Compiling from source

khronos_api makes use of git submodules. You will need to initialize these before building:

git submodule update --init

webgl_generator

README

Code generators for creating bindings to the WebGL APIs.

[build-dependencies]
webgl_generator = "0.2.0"

View on Github

6 - Glium/glium:

Safe OpenGL wrapper for the Rust language.

Note to current and future Glium users:

Glium is no longer actively developed by its original author. That said, PRs are still welcome and maintenance is continued by the surrounding community.

Elegant and safe OpenGL wrapper.

Glium is an intermediate layer between OpenGL and your application. You still need to manually handle the graphics pipeline, but without having to use OpenGL's old and error-prone API.

[dependencies] glium = "*"

Its objectives:

  • Be safe to use. Many aspects of OpenGL that can trigger a crash if misused are automatically handled by glium.
  • Provide an API that enforces good practices such as RAII or stateless function calls.
  • Be compatible with all OpenGL versions that support shaders, providing a unified API when things diverge.
  • Avoid all OpenGL errors beforehand.
  • Produce optimized OpenGL function calls, and allow the user to easily use modern OpenGL techniques.

Why should I use Glium instead of raw OpenGL calls?

Easy to use:

Functions are higher level in glium than in OpenGL. Glium's API tries to be as Rusty as possible, and shouldn't be much different than using any other Rust library. Glium should allow you to do everything that OpenGL allows you to do, just through high-level functions. If something is missing, please open an issue.

You can directly pass vectors, matrices and images to glium instead of manipulating low-level data.

Thanks to glutin, glium is very easy to setup compared to raw OpenGL.

Glium provides easier ways to do common tasks. For example the VertexBuffer struct contains information about the vertex bindings, because you usually don't use several different bindings with the same vertex buffer. This reduces the overall complexity of OpenGL.

Glium handles framebuffer objects, samplers, and vertex array objects for you. You no longer need to create them explicitly as they are automatically created when needed and destroyed when their corresponding object is destroyed.

Glium is stateless. There are no set_something() functions in the entire library, and everything is done by parameter passing. The same set of function calls will always produce the same results, which greatly reduces the number of potential problems.

Safety:

Glium detects what would normally be errors or undefined behaviors in OpenGL, and panics, without calling glGetError which would be too slow. Examples include requesting a depth test when you don't have a depth buffer available, not binding any value to an attribute or uniform, or binding multiple textures with different dimensions to the same framebuffer.

If the OpenGL context triggers an error, then you have found a bug in glium. Please open an issue. Just like Rust does everything it can to avoid crashes, glium does everything it can to avoid OpenGL errors.

The OpenGL context is automatically handled by glium. You don't need to worry about thread safety, as it is forbidden to change the thread in which OpenGL objects operate. Glium also allows you to safely replace the current OpenGL context with another one that shares the same lists.

Glium enforces RAII. Creating a Texture2d struct creates a texture, and destroying the struct destroys the texture. It also uses Rust's borrow system to ensure that objects are still alive and in the right state when you use them. Glium provides the same guarantees with OpenGL objects that you have with regular objects in Rust.

High-level functions are much easier to use and thus less error-prone. For example there is no risk of making a mistake while specifying the names and offsets of your vertex attributes, since Glium automatically generates this data for you.

Robustness is automatically handled. If the OpenGL context is lost (because of a crash in the driver for example) then swapping buffers will return an error.

View on Github

7 - PistonDevelopers/glfw-rs:

GLFW3 bindings and idiomatic wrapper for Rust.

Example

extern crate glfw;

use glfw::{Action, Context, Key};

fn main() {
    let mut glfw = glfw::init(glfw::FAIL_ON_ERRORS).unwrap();

    let (mut window, events) = glfw.create_window(300, 300, "Hello this is window", glfw::WindowMode::Windowed)
        .expect("Failed to create GLFW window.");

    window.set_key_polling(true);
    window.make_current();

    while !window.should_close() {
        glfw.poll_events();
        for (_, event) in glfw::flush_messages(&events) {
            handle_window_event(&mut window, event);
        }
    }
}

fn handle_window_event(window: &mut glfw::Window, event: glfw::WindowEvent) {
    match event {
        glfw::WindowEvent::Key(Key::Escape, _, Action::Press, _) => {
            window.set_should_close(true)
        }
        _ => {}
    }
}

Using glfw-rs

Prerequisites

Make sure you have compiled and installed GLFW 3.x. You might be able to find it on your package manager, for example on OS X: brew install glfw3 (you may need to run brew tap homebrew/versions). If not you can download and build the library from the source supplied on the GLFW website. Note that if you compile GLFW with CMake on Linux, you will have to supply the -DCMAKE_C_FLAGS=-fPIC argument. You may install GLFW to your PATH, otherwise you will have to specify the directory containing the library binaries when you call make or make lib:

GLFW_LIB_DIR=path/to/glfw/lib/directory make

Including glfw-rs in your project

Add this to your Cargo.toml:

[dependencies.glfw]
git = "https://github.com/bjz/glfw-rs.git"

On Windows

By default, glfw-rs will try to compile the glfw library. If you want to link to your custom build of glfw or if the build doesn't work (which is probably the case on Windows), you can disable this:

[dependencies.glfw]
git = "https://github.com/bjz/glfw-rs.git"
default-features = false

View on Github

8 - FSchutt/printpdf:

PDF writing library.

printpdf is a library designed for creating printable PDF documents.

[dependencies]
printpdf = "0.5.0"

Features

Currently, printpdf can only write documents, not read them.

  • Page generation
  • Layers (Illustrator like layers)
  • Graphics (lines, shapes, bezier curves)
  • Images (currently BMP/PNG/JPG only or generate your own images)
  • Embedded fonts (TTF and OTF) with Unicode support
  • Advanced graphics - overprint control, blending modes, etc.
  • Advanced typography - character scaling, character spacing, superscript, subscript, outlining, etc.
  • PDF layers (you should be able to open the PDF in Illustrator and have the layers appear)

Getting started

Writing PDF

Simple page

use printpdf::*;
use std::fs::File;
use std::io::BufWriter;

let (doc, page1, layer1) = PdfDocument::new("PDF_Document_title", Mm(247.0), Mm(210.0), "Layer 1");
let (page2, layer1) = doc.add_page(Mm(10.0), Mm(250.0),"Page 2, Layer 1");

doc.save(&mut BufWriter::new(File::create("test_working.pdf").unwrap())).unwrap();

Adding graphical shapes

use printpdf::*;
use std::fs::File;
use std::io::BufWriter;
use std::iter::FromIterator;

let (doc, page1, layer1) = PdfDocument::new("printpdf graphics test", Mm(297.0), Mm(210.0), "Layer 1");
let current_layer = doc.get_page(page1).get_layer(layer1);

// Quadratic shape. The "false" determines if the next (following)
// point is a bezier handle (for curves)
// If you want holes, simply reorder the winding of the points to be
// counterclockwise instead of clockwise.
let points1 = vec![(Point::new(Mm(100.0), Mm(100.0)), false),
                   (Point::new(Mm(100.0), Mm(200.0)), false),
                   (Point::new(Mm(300.0), Mm(200.0)), false),
                   (Point::new(Mm(300.0), Mm(100.0)), false)];

// Is the shape stroked? Is the shape closed? Is the shape filled?
let line1 = Line {
    points: points1,
    is_closed: true,
    has_fill: true,
    has_stroke: true,
    is_clipping_path: false,
};

// Triangle shape
// Note: Line is invisible by default, the previous method of
// constructing a line is recommended!
let mut line2 = Line::from_iter(vec![
    (Point::new(Mm(150.0), Mm(150.0)), false),
    (Point::new(Mm(150.0), Mm(250.0)), false),
    (Point::new(Mm(350.0), Mm(250.0)), false)]);

line2.set_stroke(true);
line2.set_closed(false);
line2.set_fill(false);
line2.set_as_clipping_path(false);

let fill_color = Color::Cmyk(Cmyk::new(0.0, 0.23, 0.0, 0.0, None));
let outline_color = Color::Rgb(Rgb::new(0.75, 1.0, 0.64, None));
let mut dash_pattern = LineDashPattern::default();
dash_pattern.dash_1 = Some(20);

current_layer.set_fill_color(fill_color);
current_layer.set_outline_color(outline_color);
current_layer.set_outline_thickness(10.0);

// Draw first line
current_layer.add_shape(line1);

let fill_color_2 = Color::Cmyk(Cmyk::new(0.0, 0.0, 0.0, 0.0, None));
let outline_color_2 = Color::Greyscale(Greyscale::new(0.45, None));

// More advanced graphical options
current_layer.set_overprint_stroke(true);
current_layer.set_blend_mode(BlendMode::Seperable(SeperableBlendMode::Multiply));
current_layer.set_line_dash_pattern(dash_pattern);
current_layer.set_line_cap_style(LineCapStyle::Round);

current_layer.set_fill_color(fill_color_2);
current_layer.set_outline_color(outline_color_2);
current_layer.set_outline_thickness(15.0);

// draw second line
current_layer.add_shape(line2);

View on Github

9 - J-F-Liu/lopdf:

PDF document manipulation.

Example Code

  • Create PDF document
use lopdf::dictionary;
use lopdf::{Document, Object, Stream};
use lopdf::content::{Content, Operation};

let mut doc = Document::with_version("1.5");
let pages_id = doc.new_object_id();
let font_id = doc.add_object(dictionary! {
    "Type" => "Font",
    "Subtype" => "Type1",
    "BaseFont" => "Courier",
});
let resources_id = doc.add_object(dictionary! {
    "Font" => dictionary! {
        "F1" => font_id,
    },
});
let content = Content {
    operations: vec![
        Operation::new("BT", vec![]),
        Operation::new("Tf", vec!["F1".into(), 48.into()]),
        Operation::new("Td", vec![100.into(), 600.into()]),
        Operation::new("Tj", vec![Object::string_literal("Hello World!")]),
        Operation::new("ET", vec![]),
    ],
};
let content_id = doc.add_object(Stream::new(dictionary! {}, content.encode().unwrap()));
let page_id = doc.add_object(dictionary! {
    "Type" => "Page",
    "Parent" => pages_id,
    "Contents" => content_id,
});
let pages = dictionary! {
    "Type" => "Pages",
    "Kids" => vec![page_id.into()],
    "Count" => 1,
    "Resources" => resources_id,
    "MediaBox" => vec![0.into(), 0.into(), 595.into(), 842.into()],
};
doc.objects.insert(pages_id, Object::Dictionary(pages));
let catalog_id = doc.add_object(dictionary! {
    "Type" => "Catalog",
    "Pages" => pages_id,
});
doc.trailer.set("Root", catalog_id);
doc.compress();

// Store file in current working directory.
// Note: Line is exclude for when running tests
if false {
    doc.save("example.pdf").unwrap();
}
  • Merge PDF documents
use lopdf::dictionary;

use std::collections::BTreeMap;

use lopdf::content::{Content, Operation};
use lopdf::{Document, Object, ObjectId, Stream, Bookmark};

pub fn generate_fake_document() -> Document {
    let mut doc = Document::with_version("1.5");
    let pages_id = doc.new_object_id();
    let font_id = doc.add_object(dictionary! {
        "Type" => "Font",
        "Subtype" => "Type1",
        "BaseFont" => "Courier",
    });
    let resources_id = doc.add_object(dictionary! {
        "Font" => dictionary! {
            "F1" => font_id,
        },
    });
    let content = Content {
        operations: vec![
            Operation::new("BT", vec![]),
            Operation::new("Tf", vec!["F1".into(), 48.into()]),
            Operation::new("Td", vec![100.into(), 600.into()]),
            Operation::new("Tj", vec![Object::string_literal("Hello World!")]),
            Operation::new("ET", vec![]),
        ],
    };
    let content_id = doc.add_object(Stream::new(dictionary! {}, content.encode().unwrap()));
    let page_id = doc.add_object(dictionary! {
        "Type" => "Page",
        "Parent" => pages_id,
        "Contents" => content_id,
        "Resources" => resources_id,
        "MediaBox" => vec![0.into(), 0.into(), 595.into(), 842.into()],
    });
    let pages = dictionary! {
        "Type" => "Pages",
        "Kids" => vec![page_id.into()],
        "Count" => 1,
    };
    doc.objects.insert(pages_id, Object::Dictionary(pages));
    let catalog_id = doc.add_object(dictionary! {
        "Type" => "Catalog",
        "Pages" => pages_id,
    });
    doc.trailer.set("Root", catalog_id);

    doc
}

fn main() -> std::io::Result<()> {
    // Generate a stack of Documents to merge
    let documents = vec![
        generate_fake_document(),
        generate_fake_document(),
        generate_fake_document(),
        generate_fake_document(),
    ];

    // Define a starting max_id (will be used as start index for object_ids)
    let mut max_id = 1;
    let mut pagenum = 1;
    // Collect all Documents Objects grouped by a map
    let mut documents_pages = BTreeMap::new();
    let mut documents_objects = BTreeMap::new();
    let mut document = Document::with_version("1.5");

    for mut doc in documents {
        let mut first = false;
        doc.renumber_objects_with(max_id);

        max_id = doc.max_id + 1;

        documents_pages.extend(
            doc
                    .get_pages()
                    .into_iter()
                    .map(|(_, object_id)| {
                        if !first {
                            let bookmark = Bookmark::new(String::from(format!("Page_{}", pagenum)), [0.0, 0.0, 1.0], 0, object_id);
                            document.add_bookmark(bookmark, None);
                            first = true;
                            pagenum += 1;
                        }

                        (
                            object_id,
                            doc.get_object(object_id).unwrap().to_owned(),
                        )
                    })
                    .collect::<BTreeMap<ObjectId, Object>>(),
        );
        documents_objects.extend(doc.objects);
    }

    // Catalog and Pages are mandatory
    let mut catalog_object: Option<(ObjectId, Object)> = None;
    let mut pages_object: Option<(ObjectId, Object)> = None;

    // Process all objects except "Page" type
    for (object_id, object) in documents_objects.iter() {
        // We have to ignore "Page" (as are processed later), "Outlines" and "Outline" objects
        // All other objects should be collected and inserted into the main Document
        match object.type_name().unwrap_or("") {
            "Catalog" => {
                // Collect a first "Catalog" object and use it for the future "Pages"
                catalog_object = Some((
                    if let Some((id, _)) = catalog_object {
                        id
                    } else {
                        *object_id
                    },
                    object.clone(),
                ));
            }
            "Pages" => {
                // Collect and update a first "Pages" object and use it for the future "Catalog"
                // We have also to merge all dictionaries of the old and the new "Pages" object
                if let Ok(dictionary) = object.as_dict() {
                    let mut dictionary = dictionary.clone();
                    if let Some((_, ref object)) = pages_object {
                        if let Ok(old_dictionary) = object.as_dict() {
                            dictionary.extend(old_dictionary);
                        }
                    }

                    pages_object = Some((
                        if let Some((id, _)) = pages_object {
                            id
                        } else {
                            *object_id
                        },
                        Object::Dictionary(dictionary),
                    ));
                }
            }
            "Page" => {}     // Ignored, processed later and separately
            "Outlines" => {} // Ignored, not supported yet
            "Outline" => {}  // Ignored, not supported yet
            _ => {
                document.objects.insert(*object_id, object.clone());
            }
        }
    }

    // If no "Pages" found abort
    if pages_object.is_none() {
        println!("Pages root not found.");

        return Ok(());
    }

    // Iter over all "Page" and collect with the parent "Pages" created before
    for (object_id, object) in documents_pages.iter() {
        if let Ok(dictionary) = object.as_dict() {
            let mut dictionary = dictionary.clone();
            dictionary.set("Parent", pages_object.as_ref().unwrap().0);

            document
                    .objects
                    .insert(*object_id, Object::Dictionary(dictionary));
        }
    }

    // If no "Catalog" found abort
    if catalog_object.is_none() {
        println!("Catalog root not found.");

        return Ok(());
    }

    let catalog_object = catalog_object.unwrap();
    let pages_object = pages_object.unwrap();

    // Build a new "Pages" with updated fields
    if let Ok(dictionary) = pages_object.1.as_dict() {
        let mut dictionary = dictionary.clone();

        // Set new pages count
        dictionary.set("Count", documents_pages.len() as u32);

        // Set new "Kids" list (collected from documents pages) for "Pages"
        dictionary.set(
            "Kids",
            documents_pages
                    .into_iter()
                    .map(|(object_id, _)| Object::Reference(object_id))
                    .collect::<Vec<_>>(),
        );

        document
                .objects
                .insert(pages_object.0, Object::Dictionary(dictionary));
    }

    // Build a new "Catalog" with updated fields
    if let Ok(dictionary) = catalog_object.1.as_dict() {
        let mut dictionary = dictionary.clone();
        dictionary.set("Pages", pages_object.0);
        dictionary.remove(b"Outlines"); // Outlines not supported in merged PDFs

        document
                .objects
                .insert(catalog_object.0, Object::Dictionary(dictionary));
    }

    document.trailer.set("Root", catalog_object.0);

    // Update the max internal ID as wasn't updated before due to direct objects insertion
    document.max_id = document.objects.len() as u32;

    // Reorder all new Document objects
    document.renumber_objects();

     //Set any Bookmarks to the First child if they are not set to a page
    document.adjust_zero_pages();

    //Set all bookmarks to the PDF Object tree then set the Outlines to the Bookmark content map.
    if let Some(n) = document.build_outline() {
        if let Ok(x) = document.get_object_mut(catalog_object.0) {
            if let Object::Dictionary(ref mut dict) = x {
                dict.set("Outlines", Object::Reference(n));
            }
        }
    }

    document.compress();

    // Save the merged PDF
    // Store file in current working directory.
    // Note: Line is exclude for when running tests
    if false {
        document.save("merged.pdf").unwrap();
    }

    Ok(())
}

View on Github

10 - Kaj/rust-pdf:

Generating PDF files in pure Rust.

A pure rust library for generating PDF files. Currently, simple vector graphics and text set in the 14 built-in fonts are supported.  

To use this library, add it as a dependency in your Cargo.toml:

[dependencies]
pdf-canvas = "*"

The API is still very alpha, usage may change. Some examples, that should work with the version containing them, can be found in the examples directory. Read the API documentation for the pdf-canvas crate. A larger example of a program using this crate is chord3, a chopro formatter.

View on Github

Thank you for following this article.

Related videos:

Intro to Rust-lang (Games and Graphics with Piston; Pong game)

#rust #graphic 

Awesome  Rust

Awesome Rust

1658878980

Git Branchless: Branchless Workflow for Git Built on Rust

Branchless workflow for Git

(This suite of tools is 100% compatible with branches. If you think this is confusing, you can suggest a new name here.)

About

git-branchless is a suite of tools which enhances Git in several ways:

It makes Git easier to use, both for novices and for power users. Examples:

It adds more flexibility for power users. Examples:

  • Patch-stack workflows: strong support for "patch-stack" workflows as used by the Linux and Git projects, as well as at many large tech companies. (This is how Git was "meant" to be used.)
  • Prototyping and experimenting workflows: strong support for prototyping and experimental work via "divergent" development.
  • git sync: to rebase all local commit stacks and branches without having to check them out first.
  • git move: The ability to move subtrees rather than "sticks" while cleaning up old branches, not touching the working copy, etc.
  • Anonymous branching: reduces the overhead of branching for experimental work.
  • In-memory operations: to modify the commit graph without having to check out the commits in question.
  • git next/prev: to quickly jump between commits and branches in a commit stack.
  • git co -i/--interactive: to interactively select a commit to check out.

It provides faster operations for large repositories and monorepos, particularly at large tech companies. Examples:

  • See the blog post Lightning-fast rebases with git-move.
  • Performance tested: benchmarked on torvalds/linux (1M+ commits) and mozilla/gecko-dev (700k+ commits).
  • Operates in-memory: avoids touching the working copy by default (which can slow down git status or invalidate build artifacts).
  • Sparse indexes: uses a custom implementation of sparse indexes for fast commit and merge operations.
  • Segmented changelog DAG: for efficient queries on the commit graph, such as merge-base calculation in O(log n) instead of O(n).
  • Ahead-of-time compiled: written in an ahead-of-time compiled language with good runtime performance (Rust).
  • Multithreading: distributes work across multiple CPU cores where appropriate.
  • To my knowledge, git-branchless provides the fastest implementation of rebase among Git tools and UIs, for the above reasons.

See also the User guide and Design goals.

Demos

Repair

Undo almost anything:

  • Commits.
  • Amended commits.
  • Merges and rebases (e.g. if you resolved a conflict wrongly).
  • Checkouts.
  • Branch creations, updates, and deletions.

Why not git reflog?

git reflog is a tool to view the previous position of a single reference (like HEAD), which can be used to undo operations. But since it only tracks the position of a single reference, complicated operations like rebases can be tedious to reverse-engineer. git undo operates at a higher level of abstraction: the entire state of your repository.

git reflog also fundamentally can't be used to undo some rare operations, such as certain branch creations, updates, and deletions. See the architecture document for more details.

What doesn't git undo handle?

git undo relies on features in recent versions of Git to work properly. See the compatibility chart.

Currently, git undo can't undo the following. You can find the design document to handle some of these cases in issue #10.

  • "Uncommitting" a commit by undoing the commit and restoring its changes to the working copy.
    • In stock Git, this can be accomplished with git reset HEAD^.
    • This scenario would be better implemented with a custom git uncommit command instead. See issue #3.
  • Undoing the staging or unstaging of files. This is tracked by issue #10 above.
  • Undoing back into the middle of a conflict, such that git status shows a message like path/to/file (both modified), so that you can resolve that specific conflict differently. This is tracked by issue #10 above.

Fundamentally, git undo is not intended to handle changes to untracked files.

Comparison to other Git undo tools

  • gitjk: Requires a shell alias. Only undoes most recent command. Only handles some Git operations (e.g. doesn't handle rebases).
  • git-extras/git-undo: Only undoes commits at current HEAD.
  • git-annex undo: Only undoes the most recent change to a given file or directory.
  • thefuck: Only undoes historical shell commands. Only handles some Git operations (e.g. doesn't handle rebases).

Visualize

Visualize your commit history with the smartlog (git sl):

Why not `git log --graph`?

git log --graph only shows commits which have branches attached with them. If you prefer to work without branches, then git log --graph won't work for you.

To support users who rewrite their commit graph extensively, git sl also points out commits which have been abandoned and need to be repaired (descendants of commits marked with rewritten as abcd1234). They can be automatically fixed up with git restack, or manually handled.

Manipulate

Edit your commit graph without fear:

Why not `git rebase -i`?

Interactive rebasing with git rebase -i is fully supported, but it has a couple of shortcomings:

  • git rebase -i can only repair linear series of commits, not trees. If you modify a commit with multiple children, then you have to be sure to rebase all of the other children commits appropriately.
  • You have to commit to a plan of action before starting the rebase. For some use-cases, it can be easier to operate on individual commits at a time, rather than an entire series of commits all at once.

When you use git rebase -i with git-branchless, you will be prompted to repair your commit graph if you abandon any commits.

Installation

See https://github.com/arxanas/git-branchless/wiki/Installation.

Short version: run cargo install --locked git-branchless, then run git branchless init in your repository.

Status

git-branchless is currently in alpha. Be prepared for breaking changes, as some of the workflows and architecture may change in the future. It's believed that there are no major bugs, but it has not yet been comprehensively battle-tested. You can see the known issues in the issue tracker.

git-branchless follows semantic versioning. New 0.x.y versions, and new major versions after reaching 1.0.0, may change the on-disk format in a backward-incompatible way.

To be notified about new versions, select Watch » Custom » Releases in Github's notifications menu at the top of the page. Or use GitPunch to deliver notifications by email.

Related tools

There's a lot of promising tooling developing in this space. See Related tools for more information.

Contributing

Thanks for your interest in contributing! If you'd like, I'm happy to set up a call to help you onboard.

For code contributions, check out the Runbook to understand how to set up a development workflow, and the Coding guidelines. You may also want to read the Architecture documentation.

For contributing documentation, see the Wiki style guide.

Contributors should abide by the Code of Conduct.

Download details:
Author: arxanas
Source code: https://github.com/arxanas/git-branchless
License: GPL-2.0 license

#rust #rustlang #git

张 小龙

1589617221

Rust vs Go - Which Is More Popular?

Go and Rust are two of the hottest compiled programming languages. I develop in Go full-time and love it, and I’m learning more about Rust recently – its an exciting language. Let’s explore some differences between the two and look at which is growing faster in the popularity polls.

#Engineering #Golang #Programming #Rust #comparison #go #popular #rust

Connor Mills

Connor Mills

1670560264

Understanding Arrays in Python

Learn how to use Python arrays. Create arrays in Python using the array module. You'll see how to define them and the different methods commonly used for performing operations on them.
 

The artcile covers arrays that you create by importing the array module. We won't cover NumPy arrays here.

Table of Contents

  1. Introduction to Arrays
    1. The differences between Lists and Arrays
    2. When to use arrays
  2. How to use arrays
    1. Define arrays
    2. Find the length of arrays
    3. Array indexing
    4. Search through arrays
    5. Loop through arrays
    6. Slice an array
  3. Array methods for performing operations
    1. Change an existing value
    2. Add a new value
    3. Remove a value
  4. Conclusion

Let's get started!


What are Python Arrays?

Arrays are a fundamental data structure, and an important part of most programming languages. In Python, they are containers which are able to store more than one item at the same time.

Specifically, they are an ordered collection of elements with every value being of the same data type. That is the most important thing to remember about Python arrays - the fact that they can only hold a sequence of multiple items that are of the same type.

What's the Difference between Python Lists and Python Arrays?

Lists are one of the most common data structures in Python, and a core part of the language.

Lists and arrays behave similarly.

Just like arrays, lists are an ordered sequence of elements.

They are also mutable and not fixed in size, which means they can grow and shrink throughout the life of the program. Items can be added and removed, making them very flexible to work with.

However, lists and arrays are not the same thing.

Lists store items that are of various data types. This means that a list can contain integers, floating point numbers, strings, or any other Python data type, at the same time. That is not the case with arrays.

As mentioned in the section above, arrays store only items that are of the same single data type. There are arrays that contain only integers, or only floating point numbers, or only any other Python data type you want to use.

When to Use Python Arrays

Lists are built into the Python programming language, whereas arrays aren't. Arrays are not a built-in data structure, and therefore need to be imported via the array module in order to be used.

Arrays of the array module are a thin wrapper over C arrays, and are useful when you want to work with homogeneous data.

They are also more compact and take up less memory and space which makes them more size efficient compared to lists.

If you want to perform mathematical calculations, then you should use NumPy arrays by importing the NumPy package. Besides that, you should just use Python arrays when you really need to, as lists work in a similar way and are more flexible to work with.

How to Use Arrays in Python

In order to create Python arrays, you'll first have to import the array module which contains all the necassary functions.

There are three ways you can import the array module:

  1. By using import array at the top of the file. This includes the module array. You would then go on to create an array using array.array().
import array

#how you would create an array
array.array()
  1. Instead of having to type array.array() all the time, you could use import array as arr at the top of the file, instead of import array alone. You would then create an array by typing arr.array(). The arr acts as an alias name, with the array constructor then immediately following it.
import array as arr

#how you would create an array
arr.array()
  1. Lastly, you could also use from array import *, with * importing all the functionalities available. You would then create an array by writing the array() constructor alone.
from array import *

#how you would create an array
array()

How to Define Arrays in Python

Once you've imported the array module, you can then go on to define a Python array.

The general syntax for creating an array looks like this:

variable_name = array(typecode,[elements])

Let's break it down:

  • variable_name would be the name of the array.
  • The typecode specifies what kind of elements would be stored in the array. Whether it would be an array of integers, an array of floats or an array of any other Python data type. Remember that all elements should be of the same data type.
  • Inside square brackets you mention the elements that would be stored in the array, with each element being separated by a comma. You can also create an empty array by just writing variable_name = array(typecode) alone, without any elements.

Below is a typecode table, with the different typecodes that can be used with the different data types when defining Python arrays:

TYPECODEC TYPEPYTHON TYPESIZE
'b'signed charint1
'B'unsigned charint1
'u'wchar_tUnicode character2
'h'signed shortint2
'H'unsigned shortint2
'i'signed intint2
'I'unsigned intint2
'l'signed longint4
'L'unsigned longint4
'q'signed long longint8
'Q'unsigned long longint8
'f'floatfloat4
'd'doublefloat8

Tying everything together, here is an example of how you would define an array in Python:

import array as arr 

numbers = arr.array('i',[10,20,30])


print(numbers)

#output

#array('i', [10, 20, 30])

Let's break it down:

  • First we included the array module, in this case with import array as arr .
  • Then, we created a numbers array.
  • We used arr.array() because of import array as arr .
  • Inside the array() constructor, we first included i, for signed integer. Signed integer means that the array can include positive and negative values. Unsigned integer, with H for example, would mean that no negative values are allowed.
  • Lastly, we included the values to be stored in the array in square brackets.

Keep in mind that if you tried to include values that were not of i typecode, meaning they were not integer values, you would get an error:

import array as arr 

numbers = arr.array('i',[10.0,20,30])


print(numbers)

#output

#Traceback (most recent call last):
# File "/Users/dionysialemonaki/python_articles/demo.py", line 14, in <module>
#   numbers = arr.array('i',[10.0,20,30])
#TypeError: 'float' object cannot be interpreted as an integer

In the example above, I tried to include a floating point number in the array. I got an error because this is meant to be an integer array only.

Another way to create an array is the following:

from array import *

#an array of floating point values
numbers = array('d',[10.0,20.0,30.0])

print(numbers)

#output

#array('d', [10.0, 20.0, 30.0])

The example above imported the array module via from array import * and created an array numbers of float data type. This means that it holds only floating point numbers, which is specified with the 'd' typecode.

How to Find the Length of an Array in Python

To find out the exact number of elements contained in an array, use the built-in len() method.

It will return the integer number that is equal to the total number of elements in the array you specify.

import array as arr 

numbers = arr.array('i',[10,20,30])


print(len(numbers))

#output
# 3

In the example above, the array contained three elements – 10, 20, 30 – so the length of numbers is 3.

Array Indexing and How to Access Individual Items in an Array in Python

Each item in an array has a specific address. Individual items are accessed by referencing their index number.

Indexing in Python, and in all programming languages and computing in general, starts at 0. It is important to remember that counting starts at 0 and not at 1.

To access an element, you first write the name of the array followed by square brackets. Inside the square brackets you include the item's index number.

The general syntax would look something like this:

array_name[index_value_of_item]

Here is how you would access each individual element in an array:

import array as arr 

numbers = arr.array('i',[10,20,30])

print(numbers[0]) # gets the 1st element
print(numbers[1]) # gets the 2nd element
print(numbers[2]) # gets the 3rd element

#output

#10
#20
#30

Remember that the index value of the last element of an array is always one less than the length of the array. Where n is the length of the array, n - 1 will be the index value of the last item.

Note that you can also access each individual element using negative indexing.

With negative indexing, the last element would have an index of -1, the second to last element would have an index of -2, and so on.

Here is how you would get each item in an array using that method:

import array as arr 

numbers = arr.array('i',[10,20,30])

print(numbers[-1]) #gets last item
print(numbers[-2]) #gets second to last item
print(numbers[-3]) #gets first item
 
#output

#30
#20
#10

How to Search Through an Array in Python

You can find out an element's index number by using the index() method.

You pass the value of the element being searched as the argument to the method, and the element's index number is returned.

import array as arr 

numbers = arr.array('i',[10,20,30])

#search for the index of the value 10
print(numbers.index(10))

#output

#0

If there is more than one element with the same value, the index of the first instance of the value will be returned:

import array as arr 


numbers = arr.array('i',[10,20,30,10,20,30])

#search for the index of the value 10
#will return the index number of the first instance of the value 10
print(numbers.index(10))

#output

#0

How to Loop through an Array in Python

You've seen how to access each individual element in an array and print it out on its own.

You've also seen how to print the array, using the print() method. That method gives the following result:

import array as arr 

numbers = arr.array('i',[10,20,30])

print(numbers)

#output

#array('i', [10, 20, 30])

What if you want to print each value one by one?

This is where a loop comes in handy. You can loop through the array and print out each value, one-by-one, with each loop iteration.

For this you can use a simple for loop:

import array as arr 

numbers = arr.array('i',[10,20,30])

for number in numbers:
    print(number)
    
#output
#10
#20
#30

You could also use the range() function, and pass the len() method as its parameter. This would give the same result as above:

import array as arr  

values = arr.array('i',[10,20,30])

#prints each individual value in the array
for value in range(len(values)):
    print(values[value])

#output

#10
#20
#30

How to Slice an Array in Python

To access a specific range of values inside the array, use the slicing operator, which is a colon :.

When using the slicing operator and you only include one value, the counting starts from 0 by default. It gets the first item, and goes up to but not including the index number you specify.


import array as arr 

#original array
numbers = arr.array('i',[10,20,30])

#get the values 10 and 20 only
print(numbers[:2])  #first to second position

#output

#array('i', [10, 20])

When you pass two numbers as arguments, you specify a range of numbers. In this case, the counting starts at the position of the first number in the range, and up to but not including the second one:

import array as arr 

#original array
numbers = arr.array('i',[10,20,30])


#get the values 20 and 30 only
print(numbers[1:3]) #second to third position

#output

#rray('i', [20, 30])

Methods For Performing Operations on Arrays in Python

Arrays are mutable, which means they are changeable. You can change the value of the different items, add new ones, or remove any you don't want in your program anymore.

Let's see some of the most commonly used methods which are used for performing operations on arrays.

How to Change the Value of an Item in an Array

You can change the value of a specific element by speficying its position and assigning it a new value:

import array as arr 

#original array
numbers = arr.array('i',[10,20,30])

#change the first element
#change it from having a value of 10 to having a value of 40
numbers[0] = 40

print(numbers)

#output

#array('i', [40, 20, 30])

How to Add a New Value to an Array

To add one single value at the end of an array, use the append() method:

import array as arr 

#original array
numbers = arr.array('i',[10,20,30])

#add the integer 40 to the end of numbers
numbers.append(40)

print(numbers)

#output

#array('i', [10, 20, 30, 40])

Be aware that the new item you add needs to be the same data type as the rest of the items in the array.

Look what happens when I try to add a float to an array of integers:

import array as arr 

#original array
numbers = arr.array('i',[10,20,30])

#add the integer 40 to the end of numbers
numbers.append(40.0)

print(numbers)

#output

#Traceback (most recent call last):
#  File "/Users/dionysialemonaki/python_articles/demo.py", line 19, in <module>
#   numbers.append(40.0)
#TypeError: 'float' object cannot be interpreted as an integer

But what if you want to add more than one value to the end an array?

Use the extend() method, which takes an iterable (such as a list of items) as an argument. Again, make sure that the new items are all the same data type.

import array as arr 

#original array
numbers = arr.array('i',[10,20,30])

#add the integers 40,50,60 to the end of numbers
#The numbers need to be enclosed in square brackets

numbers.extend([40,50,60])

print(numbers)

#output

#array('i', [10, 20, 30, 40, 50, 60])

And what if you don't want to add an item to the end of an array? Use the insert() method, to add an item at a specific position.

The insert() function takes two arguments: the index number of the position the new element will be inserted, and the value of the new element.

import array as arr 

#original array
numbers = arr.array('i',[10,20,30])

#add the integer 40 in the first position
#remember indexing starts at 0

numbers.insert(0,40)

print(numbers)

#output

#array('i', [40, 10, 20, 30])

How to Remove a Value from an Array

To remove an element from an array, use the remove() method and include the value as an argument to the method.

import array as arr 

#original array
numbers = arr.array('i',[10,20,30])

numbers.remove(10)

print(numbers)

#output

#array('i', [20, 30])

With remove(), only the first instance of the value you pass as an argument will be removed.

See what happens when there are more than one identical values:


import array as arr 

#original array
numbers = arr.array('i',[10,20,30,10,20])

numbers.remove(10)

print(numbers)

#output

#array('i', [20, 30, 10, 20])

Only the first occurence of 10 is removed.

You can also use the pop() method, and specify the position of the element to be removed:

import array as arr 

#original array
numbers = arr.array('i',[10,20,30,10,20])

#remove the first instance of 10
numbers.pop(0)

print(numbers)

#output

#array('i', [20, 30, 10, 20])

Conclusion

And there you have it - you now know the basics of how to create arrays in Python using the array module. Hopefully you found this guide helpful.

You'll start from the basics and learn in an interacitve and beginner-friendly way. You'll also build five projects at the end to put into practice and help reinforce what you learned.

Thanks for reading and happy coding!

Original article source at https://www.freecodecamp.org

#python