GeeSharp: Pan-sharpening in The Earth Engine Code Editor

geeSharp

Pan-sharpen multispectral imagery in the Google Earth Engine Code Editor with one line of code:

var sharp = geeSharp.sharpen(ms, pan);

Usage

Pan-sharpening

To pan-sharpen an image, separate the lower resolution multispectral bands and the higher resolution panchromatic band into two images and pass them to the geeSharp.sharpen function. For example:

// Import the geeSharp module
var geeSharp = require("users/aazuspan/geeSharp:geeSharp");

// Load an example Landsat 8 TOA image to sharpen
var img = ee.Image("LANDSAT/LC08/C01/T1_TOA/LC08_047027_20160819");

// Select the 30 m spectral bands to sharpen
var ms = img.select(["B4", "B3", "B2"]);
// Select the 15 m panchromatic band
var pan = img.select(["B8"]);

// Pan-sharpen!
var sharpened = geeSharp.sharpen(ms, pan);

By default, pansharpening in geeSharp uses the Smoothing Filter-based Intensity Modulation (SFIM) algorithm because it is fast and produces consistent, high-quality results. However, you may want to experiment with other methods. You can do that by passing an algorithm name to the sharpen function.

var method = "brovey";
var sharpened = geeSharp.sharpen(ms, pan, method);

Most sharpening functions just require the unsharpened multispectral bands and the high-resolution panchromatic band as inputs, but some algorithms (like Gram-Schmidt) may accept other parameters. You can add those parameters after the method name when calling sharpen.

// The Gram-Schmidt algorithm may require additional parameters depending on the size of your image.
var method = "GS";
var geom = ee.Geometry.Point([-122.41676185101713, 47.26851080476613]).buffer(1000);
var scale = 30;
var maxPixels = 1e13;

var sharpened = geeSharp.sharpen(ms, pan, method, geom, scale, maxPixels);

Print geeSharp.methods for a full list of supported algorithms, and see the documentation for descriptions.

Image quality assessment

Image quality metrics measure the distortion between a reference image and an image that has been modified, such as a pan-sharpened image.

// Choose a metric
var metric = "RMSE";
// Reproject the unsharpened image to the sharpened resolution
var reproj = unsharpened.resample("bicubic").reproject(sharpened.projection());
// Calculate the metric
var quality = geeSharp.quality(reproj, sharpened, metric);

Note that quality metrics are affected by spatial resolution, so when comparing unsharpened and pan-sharpened images, always resample and reproject the unsharpened image to high resolution first to ensure an accurate comparison!

Most quality metrics just require an unmodified and a modified image and return a dictionary mapping band names to metric values, but some metrics require other parameters (e.g. ERGAS requires the high and low spectral resolution) and some return a single image-wise value (e.g. RASE and ERGAS). Print geeSharp.metrics for a full list of supported metrics and see the documentation for descriptions.

Author: aazuspan
Source Code: https://github.com/aazuspan/geeSharp 
License: GPL-3.0 license

#javascript #image #editor 

What is GEEK

Buddha Community

How to Use Hotwire Rails

Introduction

We are back with another exciting and much-talked-about Rails tutorial on how to use Hotwire with the Rails application. This Hotwire Rails tutorial is an alternate method for building modern web applications that consume a pinch of JavaScript.

Rails 7 Hotwire is the default front-end framework shipped with Rails 7 after it was launched. It is used to represent HTML over the wire in the Rails application. Previously, we used to add a hotwire-rails gem in our gem file and then run rails hotwire: install. However, with the introduction of Rails 7, the gem got deprecated. Now, we use turbo-rails and stimulus rails directly, which work as Hotwire’s SPA-like page accelerator and Hotwire’s modest JavaScript framework.

What is Hotwire?

Hotwire is a package of different frameworks that help to build applications. It simplifies the developer’s work for writing web pages without the need to write JavaScript, and instead sending HTML code over the wire.

Introduction to The Hotwire Framework:

1. Turbo:

It uses simplified techniques to build web applications while decreasing the usage of JavaScript in the application. Turbo offers numerous handling methods for the HTML data sent over the wire and displaying the application’s data without actually loading the entire page. It helps to maintain the simplicity of web applications without destroying the single-page application experience by using the below techniques:

Turbo Frames: Turbo Frames help to load the different sections of our markup without any dependency as it divides the page into different contexts separately called frames and updates these frames individually.
Turbo Drive: Every link doesn’t have to make the entire page reload when clicked. Only the HTML contained within the tag will be displayed.
Turbo Streams: To add real-time features to the application, this technique is used. It helps to bring real-time data to the application using CRUD actions.

2. Stimulus

It represents the JavaScript framework, which is required when JS is a requirement in the application. The interaction with the HTML is possible with the help of a stimulus, as the controllers that help those interactions are written by a stimulus.

3. Strada

Not much information is available about Strada as it has not been officially released yet. However, it works with native applications, and by using HTML bridge attributes, interaction is made possible between web applications and native apps.

Simple diagrammatic representation of Hotwire Stack:

Prerequisites For Hotwire Rails Tutorial

As we are implementing the Ruby on Rails Hotwire tutorial, make sure about the following installations before you can get started.

• Ruby on Rails
• Hotwire gem
• PostgreSQL/SQLite (choose any one database)
• Turbo Rails
• Stimulus.js

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Contact Bacancy today and hire Ruby developers to start building your dream project!

Create a new Rails Project

Find the following commands to create a rails application.

mkdir ~/projects/railshotwire
cd ~/projects/railshotwire
echo "source 'https://rubygems.org'" > Gemfile
echo "gem 'rails', '~> 7.0.0'" >> Gemfile
bundle install  
bundle exec rails new . --force -d=postgresql

Now create some files for the project, up till now no usage of Rails Hotwire can be seen.
Fire the following command in your terminal.

• For creating a default controller for the application

echo "class HomeController < ApplicationController" > app/controllers/home_controller.rb
echo "end" >> app/controllers/home_controller.rb

• For creating another controller for the application

echo "class OtherController < ApplicationController" > app/controllers/other_controller.rb
echo "end" >> app/controllers/home_controller.rb

• For creating routes for the application

echo "Rails.application.routes.draw do" > config/routes.rb
echo '  get "home/index"' >> config/routes.rb
echo '  get "other/index"' >> config/routes.rb
echo '  root to: "home#index"' >> config/routes.rb
echo 'end' >> config/routes.rb

• For creating a default view for the application

mkdir app/views/home
echo '<h1>This is Rails Hotwire homepage</h1>' > app/views/home/index.html.erb
echo '<div><%= link_to "Enter to other page", other_index_path %></div>' >> app/views/home/index.html.erb

• For creating another view for the application

mkdir app/views/other
echo '<h1>This is Another page</h1>' > app/views/other/index.html.erb
echo '<div><%= link_to "Enter to home page", root_path %></div>' >> app/views/other/index.html.erb

• For creating a database and schema.rb file for the application

bin/rails db:create
bin/rails db:migrate

• For checking the application run bin/rails s and open your browser, your running application will have the below view.

Additionally, you can clone the code and browse through the project. Here’s the source code of the repository: Rails 7 Hotwire application

Now, let’s see how Hotwire Rails can work its magic with various Turbo techniques.

Hotwire Rails: Turbo Drive

Go to your localhost:3000 on your web browser and right-click on the Inspect and open a Network tab of the DevTools of the browser.

Now click on go to another page link that appears on the home page to redirect from the home page to another page. In our Network tab, we can see that this action of navigation is achieved via XHR. It appears only the part inside HTML is reloaded, here neither the CSS is reloaded nor the JS is reloaded when the navigation action is performed.

By performing this action we can see that Turbo Drive helps to represent the HTML response without loading the full page and only follows redirect and reindeer HTML responses which helps to make the application faster to access.

Hotwire Rails: Turbo Frame

This technique helps to divide the current page into different sections called frames that can be updated separately independently when new data is added from the server.
Below we discuss the different use cases of Turbo frame like inline edition, sorting, searching, and filtering of data.

Let’s perform some practical actions to see the example of these use cases.

Make changes in the app/controllers/home_controller.rb file

#CODE

class HomeController < ApplicationController
   def turbo_frame_form
   end
   
   def turbo_frame submit
      extracted_anynumber = params[:any][:anynumber]
      render :turbo_frame_form, status: :ok, locals: {anynumber: extracted_anynumber,      comment: 'turbo_frame_submit ok' }
   end
end

Add app/views/home/turbo_frame_form.html.erb file to the application and add this content inside the file.

#CODE

<section>

    <%= turbo_frame_tag 'anyframe' do %>
            
      <div>
          <h2>Frame view</h2>
          <%= form_with scope: :any, url: turbo_frame_submit_path, local: true do |form| %>
              <%= form.label :anynumber, 'Type an integer (odd or even)', 'class' => 'my-0  d-inline'  %>
              <%= form.text_field :anynumber, type: 'number', 'required' => 'true', 'value' => "#{local_assigns[:anynumber] || 0}",  'aria-describedby' => 'anynumber' %>
              <%= form.submit 'Submit this number', 'id' => 'submit-number' %>
          <% end %>
      </div>
      <div>
        <h2>Data of the view</h2>
        <pre style="font-size: .7rem;"><%= JSON.pretty_generate(local_assigns) %></pre> 
      </div>
      
    <% end %>

</section>

Make some adjustments in routes.rb

#CODE

Rails.application.routes.draw do
  get 'home/index'
  get 'other/index'

  get '/home/turbo_frame_form' => 'home#turbo_frame_form', as: 'turbo_frame_form'
  post '/home/turbo_frame_submit' => 'home#turbo_frame_submit', as: 'turbo_frame_submit'


  root to: "home#index"
end

• Next step is to change homepage view in app/views/home/index.html.erb

#CODE

<h1>This is Rails Hotwire home page</h1>
<div><%= link_to "Enter to other page", other_index_path %></div>

<%= turbo_frame_tag 'anyframe' do %>        
  <div>
      <h2>Home view</h2>
      <%= form_with scope: :any, url: turbo_frame_submit_path, local: true do |form| %>
          <%= form.label :anynumber, 'Type an integer (odd or even)', 'class' => 'my-0  d-inline'  %>
          <%= form.text_field :anynumber, type: 'number', 'required' => 'true', 'value' => "#{local_assigns[:anynumber] || 0}",  'aria-describedby' => 'anynumber' %>
          <%= form.submit 'Submit this number', 'id' => 'submit-number' %>
      <% end %>
  <div>
<% end %>

After making all the changes, restart the rails server and refresh the browser, the default view will appear on the browser.

Now in the field enter any digit, after entering the digit click on submit button, and as the submit button is clicked we can see the Turbo Frame in action in the below screen, we can observe that the frame part changed, the first title and first link didn’t move.

Hotwire Rails: Turbo Streams

Turbo Streams deliver page updates over WebSocket, SSE or in response to form submissions by only using HTML and a series of CRUD-like operations, you are free to say that either

• Update the piece of HTML while responding to all the other actions like the post, put, patch, and delete except the GET action.
• Transmit a change to all users, without reloading the browser page.

This transmit can be represented by a simple example.

• Make changes in app/controllers/other_controller.rb file of rails application

#CODE

class OtherController < ApplicationController

  def post_something
    respond_to do |format|
      format.turbo_stream {  }
    end
  end

   end

Add the below line in routes.rb file of the application

#CODE

post '/other/post_something' => 'other#post_something', as: 'post_something'

Superb! Rails will now attempt to locate the app/views/other/post_something.turbo_stream.erb template at any moment the ‘/other/post_something’ endpoint is reached.

For this, we need to add app/views/other/post_something.turbo_stream.erb template in the rails application.

#CODE

<turbo-stream action="append" target="messages">
  <template>
    <div id="message_1">This changes the existing message!</div>
  </template>
</turbo-stream>

This states that the response will try to append the template of the turbo frame with ID “messages”.

Now change the index.html.erb file in app/views/other paths with the below content.

#CODE

<h1>This is Another page</h1>
<div><%= link_to "Enter to home page", root_path %></div>

<div style="margin-top: 3rem;">
  <%= form_with scope: :any, url: post_something_path do |form| %>
      <%= form.submit 'Post any message %>
  <% end %>
  <turbo-frame id="messages">
    <div>An empty message</div>
  </turbo-frame>
</div>

• After making all the changes, restart the rails server and refresh the browser, and go to the other page.

• Once the above screen appears, click on the Post any message button

This action shows that after submitting the response, the Turbo Streams help the developer to append the message, without reloading the page.

Another use case we can test is that rather than appending the message, the developer replaces the message. For that, we need to change the content of app/views/other/post_something.turbo_stream.erb template file and change the value of the action attribute from append to replace and check the changes in the browser.

#CODE

<turbo-stream action="replace" target="messages">
  <template>
    <div id="message_1">This changes the existing message!</div>
  </template>
</turbo-stream>

When we click on Post any message button, the message that appear below that button will get replaced with the message that is mentioned in the app/views/other/post_something.turbo_stream.erb template

Stimulus

There are some cases in an application where JS is needed, therefore to cover those scenarios we require Hotwire JS tool. Hotwire has a JS tool because in some scenarios Turbo-* tools are not sufficient. But as we know that Hotwire is used to reduce the usage of JS in an application, Stimulus considers HTML as the single source of truth. Consider the case where we have to give elements on a page some JavaScript attributes, such as data controller, data-action, and data target. For that, a stimulus controller that can access elements and receive events based on those characteristics will be created.

Make a change in app/views/other/index.html.erb template file in rails application

#CODE

<h1>This is Another page</h1>
<div><%= link_to "Enter to home page", root_path %></div>

<div style="margin-top: 2rem;">
  <%= form_with scope: :any, url: post_something_path do |form| %>
      <%= form.submit 'Post something' %>
  <% end %>
  <turbo-frame id="messages">
    <div>An empty message</div>
  </turbo-frame>
</div>

<div style="margin-top: 2rem;">
  <h2>Stimulus</h2>  
  <div data-controller="hello">
    <input data-hello-target="name" type="text">
    <button data-action="click->hello#greet">
      Greet
    </button>
    <span data-hello-target="output">
    </span>
  </div>
</div>

Make changes in the hello_controller.js in path app/JavaScript/controllers and add a stimulus controller in the file, which helps to bring the HTML into life.

#CODE

import { Controller } from "@hotwired/stimulus"

export default class extends Controller {
  static targets = [ "name", "output" ]

  greet() {
    this.outputTarget.textContent =
      `Hello, ${this.nameTarget.value}!`
  }
}

Go to your browser after making the changes in the code and click on Enter to other page link which will navigate to the localhost:3000/other/index page there you can see the changes implemented by the stimulus controller that is designed to augment your HTML with just enough behavior to make it more responsive.

With just a little bit of work, Turbo and Stimulus together offer a complete answer for applications that are quick and compelling.

Using Rails 7 Hotwire helps to load the pages at a faster speed and allows you to render templates on the server, where you have access to your whole domain model. It is a productive development experience in ROR, without compromising any of the speed or responsiveness associated with SPA.

Conclusion

We hope you were satisfied with our Rails Hotwire tutorial. Write to us at service@bacancy.com for any query that you want to resolve, or if you want us to share a tutorial on your query.

For more such solutions on RoR, check out our Ruby on Rails Tutorials. We will always strive to amaze you and cater to your needs.

Original article source at: https://www.bacancytechnology.com/

#rails #ruby 

Static Code Analysis: What It Is? How to Use It?

Static code analysis refers to the technique of approximating the runtime behavior of a program. In other words, it is the process of predicting the output of a program without actually executing it.

Lately, however, the term “Static Code Analysis” is more commonly used to refer to one of the applications of this technique rather than the technique itself — program comprehension — understanding the program and detecting issues in it (anything from syntax errors to type mismatches, performance hogs likely bugs, security loopholes, etc.). This is the usage we’d be referring to throughout this post.

“The refinement of techniques for the prompt discovery of error serves as well as any other as a hallmark of what we mean by science.”

• J. Robert Oppenheimer

Outline

We cover a lot of ground in this post. The aim is to build an understanding of static code analysis and to equip you with the basic theory, and the right tools so that you can write analyzers on your own.

We start our journey with laying down the essential parts of the pipeline which a compiler follows to understand what a piece of code does. We learn where to tap points in this pipeline to plug in our analyzers and extract meaningful information. In the latter half, we get our feet wet, and write four such static analyzers, completely from scratch, in Python.

Note that although the ideas here are discussed in light of Python, static code analyzers across all programming languages are carved out along similar lines. We chose Python because of the availability of an easy to use ast module, and wide adoption of the language itself.

How does it all work?

Before a computer can finally “understand” and execute a piece of code, it goes through a series of complicated transformations:

As you can see in the diagram (go ahead, zoom it!), the static analyzers feed on the output of these stages. To be able to better understand the static analysis techniques, let’s look at each of these steps in some more detail:

Scanning

The first thing that a compiler does when trying to understand a piece of code is to break it down into smaller chunks, also known as tokens. Tokens are akin to what words are in a language.

A token might consist of either a single character, like (, or literals (like integers, strings, e.g., 7, Bob, etc.), or reserved keywords of that language (e.g, def in Python). Characters which do not contribute towards the semantics of a program, like trailing whitespace, comments, etc. are often discarded by the scanner.

Python provides the tokenize module in its standard library to let you play around with tokens:

Python

1

import io

2

import tokenize

3

4

code = b"color = input('Enter your favourite color: ')"

5

6

for token in tokenize.tokenize(io.BytesIO(code).readline):

7

    print(token)

Python

1

TokenInfo(type=62 (ENCODING),  string='utf-8')

2

TokenInfo(type=1  (NAME),      string='color')

3

TokenInfo(type=54 (OP),        string='=')

4

TokenInfo(type=1  (NAME),      string='input')

5

TokenInfo(type=54 (OP),        string='(')

6

TokenInfo(type=3  (STRING),    string="'Enter your favourite color: '")

7

TokenInfo(type=54 (OP),        string=')')

8

TokenInfo(type=4  (NEWLINE),   string='')

9

TokenInfo(type=0  (ENDMARKER), string='')

(Note that for the sake of readability, I’ve omitted a few columns from the result above — metadata like starting index, ending index, a copy of the line on which a token occurs, etc.)

#code quality #code review #static analysis #static code analysis #code analysis #static analysis tools #code review tips #static code analyzer #static code analysis tool #static analyzer

GeeSharp: Pan-sharpening in The Earth Engine Code Editor

geeSharp

Pan-sharpen multispectral imagery in the Google Earth Engine Code Editor with one line of code:

var sharp = geeSharp.sharpen(ms, pan);

Usage

Pan-sharpening

To pan-sharpen an image, separate the lower resolution multispectral bands and the higher resolution panchromatic band into two images and pass them to the geeSharp.sharpen function. For example:

// Import the geeSharp module
var geeSharp = require("users/aazuspan/geeSharp:geeSharp");

// Load an example Landsat 8 TOA image to sharpen
var img = ee.Image("LANDSAT/LC08/C01/T1_TOA/LC08_047027_20160819");

// Select the 30 m spectral bands to sharpen
var ms = img.select(["B4", "B3", "B2"]);
// Select the 15 m panchromatic band
var pan = img.select(["B8"]);

// Pan-sharpen!
var sharpened = geeSharp.sharpen(ms, pan);

By default, pansharpening in geeSharp uses the Smoothing Filter-based Intensity Modulation (SFIM) algorithm because it is fast and produces consistent, high-quality results. However, you may want to experiment with other methods. You can do that by passing an algorithm name to the sharpen function.

var method = "brovey";
var sharpened = geeSharp.sharpen(ms, pan, method);

Most sharpening functions just require the unsharpened multispectral bands and the high-resolution panchromatic band as inputs, but some algorithms (like Gram-Schmidt) may accept other parameters. You can add those parameters after the method name when calling sharpen.

// The Gram-Schmidt algorithm may require additional parameters depending on the size of your image.
var method = "GS";
var geom = ee.Geometry.Point([-122.41676185101713, 47.26851080476613]).buffer(1000);
var scale = 30;
var maxPixels = 1e13;

var sharpened = geeSharp.sharpen(ms, pan, method, geom, scale, maxPixels);

Print geeSharp.methods for a full list of supported algorithms, and see the documentation for descriptions.

Image quality assessment

Image quality metrics measure the distortion between a reference image and an image that has been modified, such as a pan-sharpened image.

// Choose a metric
var metric = "RMSE";
// Reproject the unsharpened image to the sharpened resolution
var reproj = unsharpened.resample("bicubic").reproject(sharpened.projection());
// Calculate the metric
var quality = geeSharp.quality(reproj, sharpened, metric);

Note that quality metrics are affected by spatial resolution, so when comparing unsharpened and pan-sharpened images, always resample and reproject the unsharpened image to high resolution first to ensure an accurate comparison!

Most quality metrics just require an unmodified and a modified image and return a dictionary mapping band names to metric values, but some metrics require other parameters (e.g. ERGAS requires the high and low spectral resolution) and some return a single image-wise value (e.g. RASE and ERGAS). Print geeSharp.metrics for a full list of supported metrics and see the documentation for descriptions.

Author: aazuspan
Source Code: https://github.com/aazuspan/geeSharp 
License: GPL-3.0 license

#javascript #image #editor 

How to tell if your code actually sucks...

There is no better moment for me than starting a brand new project.

Smells like new project spirit… (Whatever it means)

Starting a new project is funny. Everything seems to be in the right place. But as the projects grow and the deadlines come closer the things begin to boiling.

So, let’s talk about signals that can tell us if our code sucks and we how we can avoid that.

Everyone is afraid of adding or removing stuff

I guess we all have known at least one project that anyone wants to touch, or heard the phrase:

It works, don’t touch it!

Well, that’s not a good signal. I know there are complex projects, big projects, but if nobody in your team can touch it without breaking something, then there is something wrong with that code.

Code is like a garden, it needs to be treat and maintained, if it grows in size or complexity with no control, then will be harder to maintain and easily can get death.

Code grows out of control when there are no conventions to work in it, team practices, even solo practices are important to keep our code under control.

If you see yourself in a scenario where is hard to add things to your project, then you should rethink the whole thing.

Only the creator understands it (Sometimes even the creator can’t.)

If only one person in your team can understand a project, then that’s a problem and hopefully that person never gets sick or goes on vacation.

If you are working by yourself please don’t write overcomplicated code; in my experience simplicity is better; writing code that anyone can read is the right thing to do.

t is clear today may not be that clear in a couple of weeks, even for you.

Use comments on your code. Do not comment on every single line but put enough comments on the complicated and crucial parts.

1

If you develop on javascript this is a great repo with good practices.

It is difficult to read

I have to insist on this. Simple is better; there is no need to show anyone how abstract you can be or how much you know the language. Keeping things simple is way much more productive than trying to show off your knowledge and skill.

Keep your code as readable as possible, simple as possible. Clear variable names, descriptive functions names, clear statements. This will save time for you and your team.

A good way to measure how readable your code is is to overcome the necessity of comments. If the code does not need many comments to describe it, then it means the code is readable enough.

Conclusion

The best code is not only the one that is fast and performant; the best code is also the one you enjoy working on. I’ve had nightmares of codebases that I had to work with, and I also have had codebases that I enjoy.

Coding is a team sport, and every member of the team must be able to play the game, so write for the team.

#development #programming #software-development #coding #coding-skills #software-engineering #code-quality #code

Guidelines for Java Code Reviews

Get a jump-start on your next code review session with this list.

Having another pair of eyes scan your code is always useful and helps you spot mistakes before you break production. You need not be an expert to review someone’s code. Some experience with the programming language and a review checklist should help you get started. We’ve put together a list of things you should keep in mind when you’re reviewing Java code. Read on!

1. Follow Java Code Conventions

2. Replace Imperative Code With Lambdas and Streams

3. Beware of the NullPointerException

4. Directly Assigning References From Client Code to a Field

5. Handle Exceptions With Care

…

#java #code quality #java tutorial #code analysis #code reviews #code review tips #code analysis tools #java tutorial for beginners #java code review