Gifuct-js: Fastest Javascript .GIF Decoder/parser

Gifuct-js

A Simple to use javascript .GIF decoder.

We needed to be able to efficiently load and manipulate GIF files for the Ruffle hybrid app (for mobiles). There are a couple of example libraries out there like jsgif & its derivative libgif-js, however these are admittedly inefficient, and a mess. After pulling our hair out trying to understand the ancient, mystic gif format (hence the project name), we decided to just roll our own. This library also removes any specific drawing code, and simply parses, and decompresses gif files so that you can manipulate and display them however you like. We do include imageData patch construction though to get you most of the way there.

Demo

You can see a demo of this library in action here

Usage

Installation:

npm install gifuct-js

Decoding:

This decoder uses js-binary-schema-parser to parse the gif files (you can examine the schema in the source). This means the gif file must firstly be converted into a Uint8Array buffer in order to decode it. Some examples:

fetch

  import { parseGIF, decompressFrames } from 'gifuct-js'

  var promisedGif = fetch(gifURL)
       .then(resp => resp.arrayBuffer())
       .then(buff => {
           var gif = parseGIF(buff)
           var frames = decompressFrames(gif, true)
           return gif;
       });

XMLHttpRequest

  import { parseGIF, decompressFrames } from 'gifuct-js'

  var oReq = new XMLHttpRequest();
  oReq.open("GET", gifURL, true);
  oReq.responseType = "arraybuffer";

  oReq.onload = function (oEvent) {
      var arrayBuffer = oReq.response; // Note: not oReq.responseText
      if (arrayBuffer) {
          var gif = parseGIF(arrayBuffer);
          var frames = decompressFrames(gif, true);
          // do something with the frame data
      }
  };

  oReq.send(null);

Result:

The result of the decompressFrames(gif, buildPatch) function returns an array of all the GIF image frames, and their meta data. Here is a an example frame:

{
    // The color table lookup index for each pixel
    pixels: [...],
    // the dimensions of the gif frame (see disposal method)
    dims: {
        top: 0,
        left: 10,
        width: 100,
        height: 50
    },
    // the time in milliseconds that this frame should be shown
    delay: 50,
    // the disposal method (see below)
    disposalType: 1,
    // an array of colors that the pixel data points to
    colorTable: [...],
    // An optional color index that represents transparency (see below)
    transparentIndex: 33,
    // Uint8ClampedArray color converted patch information for drawing
    patch: [...]
 }

Automatic Patch Generation:

If the buildPatch param of the dcompressFrames() function is true, the parser will not only return the parsed and decompressed gif frames, but will also create canvas ready Uint8ClampedArray arrays of each gif frame image, so that they can easily be drawn using ctx.putImageData() for example. This requirement is common, however it was made optional because it makes assumptions about transparency. The demo makes use of this option.

Disposal Method:

The pixel data is stored as a list of indexes for each pixel. These each point to a value in the colorTable array, which contain the color that each pixel should be drawn. Each frame of the gif may not be the full size, but instead a patch that needs to be drawn over a particular location. The disposalType defines how that patch should be drawn over the gif canvas. In most cases, that value will be 1, indicating that the gif frame should be simply drawn over the existing gif canvas without altering any pixels outside the frames patch dimensions. More can be read about this here.

Transparency:

If a transparentIndex is defined for a frame, it means that any pixel within the pixel data that matches this index should not be drawn. When drawing the patch using canvas, this means setting the alpha value for this pixel to 0.

Drawing the GIF

Check out the demo for an example of how to draw/manipulate a gif using this library. We wanted the library to be drawing agnostic to allow users to do what they wish with the raw gif data, rather than impose a method that has to be altered. On this note however, we provide an easy interface for creating commonly used canvas pixel data for drawing ease.

Thanks to

We underestimated the convolutedness of the GIF format, so this library couldn't have been made without the help of:

Project: What's In A GIF - Bit by Byte - An amazingly detailed blog by Matthew Flickinger
jsgif
The [almost correct] LZW decompression from this neat gist

Who are we?

Matt Way & Nick Drewe

Wethrift.com

Download Details:

Author: Matt-way
Source Code: https://github.com/matt-way/gifuct-js
License: MIT license

#javascript #decode #gif

What is GEEK

Buddha Community

Gifuct-js: Fastest Javascript .GIF Decoder/parser

JavaScript Daily

1632537859

NBB: Ad-hoc CLJS Scripting on Node.js

Nbb

Not babashka. Node.js babashka!?

Ad-hoc CLJS scripting on Node.js.

Status

Experimental. Please report issues here.

Goals and features

Nbb's main goal is to make it easy to get started with ad hoc CLJS scripting on Node.js.

Additional goals and features are:

Fast startup without relying on a custom version of Node.js.
Small artifact (current size is around 1.2MB).
First class macros.
Support building small TUI apps using Reagent.
Complement babashka with libraries from the Node.js ecosystem.

Requirements

Nbb requires Node.js v12 or newer.

How does this tool work?

CLJS code is evaluated through SCI, the same interpreter that powers babashka. Because SCI works with advanced compilation, the bundle size, especially when combined with other dependencies, is smaller than what you get with self-hosted CLJS. That makes startup faster. The trade-off is that execution is less performant and that only a subset of CLJS is available (e.g. no deftype, yet).

Usage

Install nbb from NPM:

$ npm install nbb -g

Omit -g for a local install.

Try out an expression:

$ nbb -e '(+ 1 2 3)'
6

And then install some other NPM libraries to use in the script. E.g.:

$ npm install csv-parse shelljs zx

Create a script which uses the NPM libraries:

(ns script
  (:require ["csv-parse/lib/sync$default" :as csv-parse]
            ["fs" :as fs]
            ["path" :as path]
            ["shelljs$default" :as sh]
            ["term-size$default" :as term-size]
            ["zx$default" :as zx]
            ["zx$fs" :as zxfs]
            [nbb.core :refer [*file*]]))

(prn (path/resolve "."))

(prn (term-size))

(println (count (str (fs/readFileSync *file*))))

(prn (sh/ls "."))

(prn (csv-parse "foo,bar"))

(prn (zxfs/existsSync *file*))

(zx/$ #js ["ls"])

Call the script:

$ nbb script.cljs
"/private/tmp/test-script"
#js {:columns 216, :rows 47}
510
#js ["node_modules" "package-lock.json" "package.json" "script.cljs"]
#js [#js ["foo" "bar"]]
true
$ ls
node_modules
package-lock.json
package.json
script.cljs

Macros

Nbb has first class support for macros: you can define them right inside your .cljs file, like you are used to from JVM Clojure. Consider the plet macro to make working with promises more palatable:

(defmacro plet
  [bindings & body]
  (let [binding-pairs (reverse (partition 2 bindings))
        body (cons 'do body)]
    (reduce (fn [body [sym expr]]
              (let [expr (list '.resolve 'js/Promise expr)]
                (list '.then expr (list 'clojure.core/fn (vector sym)
                                        body))))
            body
            binding-pairs)))

Using this macro we can look async code more like sync code. Consider this puppeteer example:

(-> (.launch puppeteer)
      (.then (fn [browser]
               (-> (.newPage browser)
                   (.then (fn [page]
                            (-> (.goto page "https://clojure.org")
                                (.then #(.screenshot page #js{:path "screenshot.png"}))
                                (.catch #(js/console.log %))
                                (.then #(.close browser)))))))))

Using plet this becomes:

(plet [browser (.launch puppeteer)
       page (.newPage browser)
       _ (.goto page "https://clojure.org")
       _ (-> (.screenshot page #js{:path "screenshot.png"})
             (.catch #(js/console.log %)))]
      (.close browser))

See the puppeteer example for the full code.

Since v0.0.36, nbb includes promesa which is a library to deal with promises. The above plet macro is similar to promesa.core/let.

Startup time

$ time nbb -e '(+ 1 2 3)'
6
nbb -e '(+ 1 2 3)'   0.17s  user 0.02s system 109% cpu 0.168 total

The baseline startup time for a script is about 170ms seconds on my laptop. When invoked via npx this adds another 300ms or so, so for faster startup, either use a globally installed nbb or use $(npm bin)/nbb script.cljs to bypass npx.

Dependencies

NPM dependencies

Nbb does not depend on any NPM dependencies. All NPM libraries loaded by a script are resolved relative to that script. When using the Reagent module, React is resolved in the same way as any other NPM library.

Classpath

To load .cljs files from local paths or dependencies, you can use the --classpath argument. The current dir is added to the classpath automatically. So if there is a file foo/bar.cljs relative to your current dir, then you can load it via (:require [foo.bar :as fb]). Note that nbb uses the same naming conventions for namespaces and directories as other Clojure tools: foo-bar in the namespace name becomes foo_bar in the directory name.

To load dependencies from the Clojure ecosystem, you can use the Clojure CLI or babashka to download them and produce a classpath:

$ classpath="$(clojure -A:nbb -Spath -Sdeps '{:aliases {:nbb {:replace-deps {com.github.seancorfield/honeysql {:git/tag "v2.0.0-rc5" :git/sha "01c3a55"}}}}}')"

and then feed it to the --classpath argument:

$ nbb --classpath "$classpath" -e "(require '[honey.sql :as sql]) (sql/format {:select :foo :from :bar :where [:= :baz 2]})"
["SELECT foo FROM bar WHERE baz = ?" 2]

Currently nbb only reads from directories, not jar files, so you are encouraged to use git libs. Support for .jar files will be added later.

Current file

The name of the file that is currently being executed is available via nbb.core/*file* or on the metadata of vars:

(ns foo
  (:require [nbb.core :refer [*file*]]))

(prn *file*) ;; "/private/tmp/foo.cljs"

(defn f [])
(prn (:file (meta #'f))) ;; "/private/tmp/foo.cljs"

Reagent

Nbb includes reagent.core which will be lazily loaded when required. You can use this together with ink to create a TUI application:

$ npm install ink

ink-demo.cljs:

(ns ink-demo
  (:require ["ink" :refer [render Text]]
            [reagent.core :as r]))

(defonce state (r/atom 0))

(doseq [n (range 1 11)]
  (js/setTimeout #(swap! state inc) (* n 500)))

(defn hello []
  [:> Text {:color "green"} "Hello, world! " @state])

(render (r/as-element [hello]))

Promesa

Working with callbacks and promises can become tedious. Since nbb v0.0.36 the promesa.core namespace is included with the let and do! macros. An example:

(ns prom
  (:require [promesa.core :as p]))

(defn sleep [ms]
  (js/Promise.
   (fn [resolve _]
     (js/setTimeout resolve ms))))

(defn do-stuff
  []
  (p/do!
   (println "Doing stuff which takes a while")
   (sleep 1000)
   1))

(p/let [a (do-stuff)
        b (inc a)
        c (do-stuff)
        d (+ b c)]
  (prn d))

$ nbb prom.cljs
Doing stuff which takes a while
Doing stuff which takes a while
3

Also see API docs.

Js-interop

Since nbb v0.0.75 applied-science/js-interop is available:

(ns example
  (:require [applied-science.js-interop :as j]))

(def o (j/lit {:a 1 :b 2 :c {:d 1}}))

(prn (j/select-keys o [:a :b])) ;; #js {:a 1, :b 2}
(prn (j/get-in o [:c :d])) ;; 1

Most of this library is supported in nbb, except the following:

destructuring using :syms
property access using .-x notation. In nbb, you must use keywords.

See the example of what is currently supported.

Examples

See the examples directory for small examples.

Also check out these projects built with nbb:

c64core: retrocompute aesthetics twitter bot
gallery.cljs: script to download walpapers from windowsonearth.org.
nbb-action-example: example of a Github action built with nbb.

API

See API documentation.

Migrating to shadow-cljs

See this gist on how to convert an nbb script or project to shadow-cljs.

Build

Prequisites:

babashka >= 0.4.0
Clojure CLI >= 1.10.3.933
Node.js 16.5.0 (lower version may work, but this is the one I used to build)

To build:

Clone and cd into this repo
bb release

Run bb tasks for more project-related tasks.

Download Details:
Author: borkdude
Download Link: Download The Source Code
Official Website: https://github.com/borkdude/nbb
License: EPL-1.0

#node #javascript

Reid Rohan

1664931000

Gifuct-js: Fastest Javascript .GIF Decoder/parser

Gifuct-js

A Simple to use javascript .GIF decoder.

We needed to be able to efficiently load and manipulate GIF files for the Ruffle hybrid app (for mobiles). There are a couple of example libraries out there like jsgif & its derivative libgif-js, however these are admittedly inefficient, and a mess. After pulling our hair out trying to understand the ancient, mystic gif format (hence the project name), we decided to just roll our own. This library also removes any specific drawing code, and simply parses, and decompresses gif files so that you can manipulate and display them however you like. We do include imageData patch construction though to get you most of the way there.

Demo

You can see a demo of this library in action here

Usage

Installation:

npm install gifuct-js

Decoding:

This decoder uses js-binary-schema-parser to parse the gif files (you can examine the schema in the source). This means the gif file must firstly be converted into a Uint8Array buffer in order to decode it. Some examples:

fetch

  import { parseGIF, decompressFrames } from 'gifuct-js'

  var promisedGif = fetch(gifURL)
       .then(resp => resp.arrayBuffer())
       .then(buff => {
           var gif = parseGIF(buff)
           var frames = decompressFrames(gif, true)
           return gif;
       });

XMLHttpRequest

  import { parseGIF, decompressFrames } from 'gifuct-js'

  var oReq = new XMLHttpRequest();
  oReq.open("GET", gifURL, true);
  oReq.responseType = "arraybuffer";

  oReq.onload = function (oEvent) {
      var arrayBuffer = oReq.response; // Note: not oReq.responseText
      if (arrayBuffer) {
          var gif = parseGIF(arrayBuffer);
          var frames = decompressFrames(gif, true);
          // do something with the frame data
      }
  };

  oReq.send(null);

Result:

The result of the decompressFrames(gif, buildPatch) function returns an array of all the GIF image frames, and their meta data. Here is a an example frame:

{
    // The color table lookup index for each pixel
    pixels: [...],
    // the dimensions of the gif frame (see disposal method)
    dims: {
        top: 0,
        left: 10,
        width: 100,
        height: 50
    },
    // the time in milliseconds that this frame should be shown
    delay: 50,
    // the disposal method (see below)
    disposalType: 1,
    // an array of colors that the pixel data points to
    colorTable: [...],
    // An optional color index that represents transparency (see below)
    transparentIndex: 33,
    // Uint8ClampedArray color converted patch information for drawing
    patch: [...]
 }

Automatic Patch Generation:

If the buildPatch param of the dcompressFrames() function is true, the parser will not only return the parsed and decompressed gif frames, but will also create canvas ready Uint8ClampedArray arrays of each gif frame image, so that they can easily be drawn using ctx.putImageData() for example. This requirement is common, however it was made optional because it makes assumptions about transparency. The demo makes use of this option.

Disposal Method:

The pixel data is stored as a list of indexes for each pixel. These each point to a value in the colorTable array, which contain the color that each pixel should be drawn. Each frame of the gif may not be the full size, but instead a patch that needs to be drawn over a particular location. The disposalType defines how that patch should be drawn over the gif canvas. In most cases, that value will be 1, indicating that the gif frame should be simply drawn over the existing gif canvas without altering any pixels outside the frames patch dimensions. More can be read about this here.

Transparency:

If a transparentIndex is defined for a frame, it means that any pixel within the pixel data that matches this index should not be drawn. When drawing the patch using canvas, this means setting the alpha value for this pixel to 0.

Drawing the GIF

Check out the demo for an example of how to draw/manipulate a gif using this library. We wanted the library to be drawing agnostic to allow users to do what they wish with the raw gif data, rather than impose a method that has to be altered. On this note however, we provide an easy interface for creating commonly used canvas pixel data for drawing ease.

Thanks to

We underestimated the convolutedness of the GIF format, so this library couldn't have been made without the help of:

Project: What's In A GIF - Bit by Byte - An amazingly detailed blog by Matthew Flickinger
jsgif
The [almost correct] LZW decompression from this neat gist

Who are we?

Matt Way & Nick Drewe

Wethrift.com

Download Details:

Author: Matt-way
Source Code: https://github.com/matt-way/gifuct-js
License: MIT license

#javascript #decode #gif

Ajay Kapoor

1626321063

JS Development Company India | JavaScript Development Services

PixelCrayons: Our JavaScript web development service offers you a feature-packed & dynamic web application that effectively caters to your business challenges and provide you the best RoI. Our JavaScript web development company works on all major frameworks & libraries like Angular, React, Nodejs, Vue.js, to name a few.

With 15+ years of domain expertise, we have successfully delivered 13800+ projects and have successfully garnered 6800+ happy customers with 97%+ client retention rate.

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Our JavaScript development companies offers you strict NDA, 100% money back guarantee and agile/DevOps approach.

#javascript development company #javascript development services #javascript web development #javascript development #javascript web development services #javascript web development company

Catharine Rippin

1593507275

Grokking Call(), Apply() and Bind() Methods in JavaScript

These functions are very important for every JavaScript Developer and are used in almost every JavaScript Library or Framework. Check out the code snippet below.

Taken from the very popular library Lodash

/**
	* Creates a function that invokes `func` with arguments reversed.
	*
	* @since 4.0.0
	* @category Function
	* @param {Function} func The function to flip arguments for.
	* @returns {Function} Returns the new flipped function.
	* @see reverse
	* @example
	*
	* const flipped = flip((...args) => args)
	*
	* flipped('a', 'b', 'c', 'd')
	* // => ['d', 'c', 'b', 'a']
	*/
	function flip(func) {
	  if (typeof func !== 'function') {
	    throw new TypeError('Expected a function')
	  }
	  return function(...args) {
	    return func.apply(this, args.reverse())
	  }
	}

	export default flip

Look at the statement on line 21, return func.apply(this, args.reverse())

In this article, we will have a look at the call(), apply() and bind() methods of JavaScript. Basically these 3 methods are used to control the invocation of the function. The call() and apply() were introduced in ECMAScript 3 while bind() was added as a part of ECMAScript 5.

Let us start with an example to understand these.

Suppose you are a student of X university and your professor has asked you to create a math library, for an assignment, which calculates the area of a circle.

const calcArea = {
	  pi: 3.14,
	  area: function(r) {
	    return this.pi * r * r;
	  }
	}

calcArea.area(4); // prints 50.24


You test this and verify its result, it is working fine and you upload the library to portal way before the deadline ends. Then you ask your classmates to test and verify as well, you come to know that that your result and their results mismatches the decimals precision. You check the assignment guidelines, Oh no! The professor asked you to use a constant **pi** with 5 decimals precision. But you used **3.14** and not **3.14159** as the value of pi. Now you cannot re-upload the library as the deadline date was already over. In this situation, **call()** function will save you.

#js #javascript-development #javascript #javascript-interview #javascript-tips

Rahul Jangid

1622207074

What is JavaScript - Stackfindover - Blog

Who invented JavaScript, how it works, as we have given information about Programming language in our previous article ( What is PHP ), but today we will talk about what is JavaScript, why JavaScript is used The Answers to all such questions and much other information about JavaScript, you are going to get here today. Hope this information will work for you.

Who invented JavaScript?

JavaScript language was invented by Brendan Eich in 1995. JavaScript is inspired by Java Programming Language. The first name of JavaScript was Mocha which was named by Marc Andreessen, Marc Andreessen is the founder of Netscape and in the same year Mocha was renamed LiveScript, and later in December 1995, it was renamed JavaScript which is still in trend.

What is JavaScript?

JavaScript is a client-side scripting language used with HTML (Hypertext Markup Language). JavaScript is an Interpreted / Oriented language called JS in programming language JavaScript code can be run on any normal web browser. To run the code of JavaScript, we have to enable JavaScript of Web Browser. But some web browsers already have JavaScript enabled.

Today almost all websites are using it as web technology, mind is that there is maximum scope in JavaScript in the coming time, so if you want to become a programmer, then you can be very beneficial to learn JavaScript.

JavaScript Hello World Program

In JavaScript, ‘document.write‘ is used to represent a string on a browser.

<script type="text/javascript">
	document.write("Hello World!");
</script>

How to comment JavaScript code?

For single line comment in JavaScript we have to use // (double slashes)
For multiple line comments we have to use / * – – * /

<script type="text/javascript">

//single line comment

/* document.write("Hello"); */

</script>

Advantages and Disadvantages of JavaScript

#javascript #javascript code #javascript hello world #what is javascript #who invented javascript