Learning Processing.js - 1-优快云博客

本文介绍Processing.js，一种用于网页上编程图像、动画及交互的开放语言。通过JavaScript在HTML5 Canvas上绘制图形并操作图片，无需使用Flash或Java Applets。文章提供了一个基本示例，演示如何设置画布大小、背景颜色等。

Learning Processing.js - 1

Processing.js is an open programming language for people who want to program images, animation, and interactions for the web without using Flash or Java applets. Processing.js uses Javascript to draw shapes and manipulate images on the HTML5 Canvas element.

Basic Syntax:

As with any language, you begin by defining your global variables. Then you create a setup() function, where you control the visualization’s properties, like the canvas size, frame rate and perhaps variables such as the stoke-weight or background-color.

The next step is to create your draw() function, which controls the behavior of each frame in your animation. The draw function loops continuously unless you tell it otherwise by using the exit() command.

Following is my first Processing.js example:

<html>
<head>
    <title></title>  

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

    <script type="text/javascript">
        window.onload = function() {
            var canvas = document.getElementById('canvas');
            var script = document.getElementById('processing').text;
            Processing(canvas, script);
        };
    </script>  

</head>
<body>  

    <script id="processing" type="application/processing">  

        int x;  

        void setup() {
            // The size function is a statement that tells the computer
            // how large to make the window.
            // Each function statement has zero or more parameters.
            // Parameters are data passed into the function
            // and used as values for specifying what the computer will do.
            size(200, 200);  

            // The background function is a statement that tells the computer
            // which color to make the background of the window
            background(100);  

            stroke(255);
            frameRate(60);    

            x = width;
        }  

        // The statements in draw() are executed until the
        // program is stopped. Each statement is executed in
        // sequence and after the last line is read, the first
        // line is executed again.
        void draw()
        {
            background(100);
            x--;
            if(x < 0) {
                x = width - 1;
            }
            line(x, 0, x, height);
        }  

    </script>  

    <canvas id="canvas"></canvas>
</body>
</html>