Processing.js

Processing.js
Original author(s) John Resig
Developer(s) Processing.js team
Initial release 2008 (2008)
Stable release
1.4.8 / March 25, 2014 (2014-03-25)
Development status Active
Written in JavaScript
Size 61 KB (gzipped) / 209 KB (production) / 754 KB (development)
Type Web application framework
License MIT
Website processingjs.org

Processing.js is a JavaScript port of Processing, a programming language designed to write visualizations, images, and interactive content. It allows web browsers to display animations, visual applications, games and other graphical rich content without the need for a Java applet or Flash plugin.

Processing.js was originally created to allow existing Processing developers and existing code to work unmodified on web. Processing.js uses JavaScript to render 2D and 3D content on the HTML canvas element, and is supported by browsers that have implemented this element (the latest versions of Mozilla Firefox, Opera, Internet Explorer, Safari and Google Chrome).

The development of Processing.js was begun by John Resig and then picked up by students at Seneca College after its initial release in 2008. A team of students finished the port of Processing.js, fixing more than 900 bugs, shipping 12 releases, and creating a vibrant community in the process. The project was done through a partnership between the Mozilla Foundation and Seneca College, led by David Humphrey, Al MacDonald, and Corban Brook. The students continue to maintain the project today.

Versions

Changes made in latest release: (2.1)

IDE

The Processing.js code is designed to be used with standalone text editors, or it may be built into an integrated development environment (IDE).

Following are the IDEs which support Processing.js:

iPhone use

There exists an integration of the Processing.js library and a Javascript application framework for iPhone, called iProcessing.

Processing syntax

Processing.js syntax is almost identical to that of the Processing language, in that a setup() function is used to define general visualization properties like canvas size, frame rate and other variables, and a draw() function controls the behavior of each frame in the animation.

The Processing.js library can be included in head section of a web page as a single JavaScript file:

<html>
<head>
  <script type="text/javascript" src="processing.js"></script>
</head>

A canvas element is declared inside the body, with a data-processing-sources attribute, specifying the location of an external file holding the Processing code:

<canvas data-processing-sources="example.pde"></canvas>

Any extension can be used in the external file, for example, the .pde extension used by the Processing language sketch files.

/* example.pde */

// The statements in the setup() function 
// execute once when the program begins
void setup() 
{
  size(200, 200);  // Sets the canvas size to 200 by 200 pixels
  stroke(255);     // Set line drawing color to monochrome white
  frameRate(30);   // Set up draw() to be called 30 times per second
}

float y = 100;

// The statements in draw() are executed until the 
// program is stopped. The function is called as many
// times per second as the frameRate. If no explicit
// rate is set, this is 45 times per second.
void draw() 
{ 
  background(0);   // Set the background to monochrome black
  y = y - 1; 
  if (y < 0) { y = height; } 
  line(0, y, width, y);  // draw a horizontal line at height y
}

Processing language has two ways of rendering a 2D or 3D in order to understand underlying graphic. It uses Java for 2D, and OpenGL for 3D. This code demonstrates the rendering . The size() function provide choice to choose 2D or 3D. To create a 2D sketch that is 100 by 100 pixels. size(100, 100, P2D);
To draw a 3D sketch OpenGL is used: size(100, 100, OPENGL);

Challenges

The sample code below shows explicit casting of the integer datatype.

// before
int g = mouseX / j;

// after
int g = (int)(mouseX / j);

See also

References

This article is issued from Wikipedia - version of the 7/6/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.