Per pixel bitmap animation in HTML5/JavaScript

LICSON showed how to simulate GLSL shader effects on HTML5 Canvas using pure JavaScript:

//The requestAnimFrame fallback for better and smoother animation
window.requestAnimFrame = (function () {
    return window.requestAnimationFrame || window.webkitRequestAnimationFrame || 
 window.mozRequestAnimationFrame || window.oRequestAnimationFrame || 
 window.msRequestAnimationFrame || function (callback) {
        window.setTimeout(callback, 1000 / 60);
    };
})();

//Prepare our canvas
var canvas = document.querySelector('#render');
var w = window.innerWidth;
var h = window.innerHeight;
canvas.width = w;
canvas.height = h;
var ctx = canvas.getContext('2d');

var time = Date.now();//record initial time
var buffer = ctx.createImageData(w, h);//The back buffer we used to paint the result into the canvas

//The main render function
//Calculate a color value from elapsed time and [x,y] coordinates (scaled to [0,1])
function render(time, fragcoord) {
    /* put the GLSL fragment shader's JavaScript equivalent here. */
    //begin of per pixel bitmap manipulation
    var x = fragcoord[0]; var y = fragcoord[1];
    var red = x;
    var green = y;
    var blue = 1/(1+time);
    var alpha = 1;
    //end of per pixel bitmap manipulation
    return [red,green,blue,alpha]; //the final color value (scaled to [0,1])
};

function animate() {
    var delta = (Date.now() - time) / 1000;
    buffer = ctx.createImageData(w, h);
    ctx.clearRect(0, 0, w, h);
    for (var x = 0; x < w; x++) {
        for (var y = 0; y < h; y++) {
            var ret = render(delta, [x/w, y/h]);
            var i = (y * buffer.width + x) * 4;
            buffer.data[i] = ret[0] * 255;//red
            buffer.data[i + 1] = ret[1] * 255;//green
            buffer.data[i + 2] = ret[2] * 255;//blue
            buffer.data[i + 3] = ret[3] * 255;//alpha
        }
    }
    ctx.putImageData(buffer, 0, 0);
    requestAnimFrame(animate);
};

window.onresize = function () {
    w = window.innerWidth;
    h = window.innerHeight;
    canvas.width = w;
    canvas.height = h;
};

animate();

Demo & Full Source Code: http://vvv.flaswf.tk/demo/?url=HTML5Pixels

The difference: In AS3/Haxe, a color value is represented by a single Unsigned Int value (0xAARRGGBB). In HTML5, the color data (BitmapData) array stores a whole color value as four neighboring elements (integer between 0 and 255), representing the red, green, blue and alpha values, respectively. To get/set the color value at coordinate (x,y), you should go to index "i=(y*buffer.width+x)*4", then the red, green, blue and alpha values are respectively "buffer.data[i], buffer.data[i+1], buffer.data[i+2], buffer.data[i+3]".

Links:
https://licson.net/post/glsl-fragment-shaders-in-javascript/
https://developer.mozilla.org/en-US/docs/Web/API/Canvas_API/Tutorial/Pixel_manipulation_with_canvas
https://bruce-lab.blogspot.com/2019/02/four-ways-for-per-pixel-bitmap.html
Faster Canvas Pixel Manipulation with Typed Arrays