edco/fizzlefade.html

## fizzlefade.html
<!DOCTYPE html>
<html>
<head><title>Javascript RT</title></head>
<style>canvas {width: 1280px; height: 768px}</style>
<body>

<canvas id="framebuffer"></canvas>

<script type="text/javascript">
/* Fizzlefade using a Feistel network.
 * Copyright (C) 2017 Salvatore Sanfilippo <antirez@gmail.com>
 * This softare is released under the terms of the BSD two-clause license.
 * See http://fabiensanglard.net/fizzlefade/index.php for more info. */

var ctx;
var pixels;
var screen_width = 3480;
var screen_height = 2160;
var frame = 0;

/* Here is a very ugly thing that calms my laptop's fan */
var timerKiller = {
    timer: null,
    ended: false,
    setTimer: function (newTimer) {
        timer = newTimer;
        if(ended) {
            clearInterval(timer);
        }
    },
    end: function () {
        if(timer != null) {
            clearInterval(timer);
        }
        ended = true;
    }
};

/* Create a context where we can easily write pixels. */
function init() {
    fb = document.getElementById('framebuffer');
    fb.width = screen_width;
    fb.height = screen_height;
    ctx = fb.getContext('2d');
    pixels = ctx.createImageData(screen_width, screen_height);
    timerKiller.setTimer(setInterval(draw, 1, timerKiller));
};

/* Write a pixel, just set alpha and RGB channels. */
function setPixel(x,y) {
    var offset = x*4+y*4*screen_width;

    pixels.data[offset+3] = 255;
    pixels.data[offset+0] = 255;
    pixels.data[offset+1] = 0;
    pixels.data[offset+2] = 0;
}

/* Transforms the n bit input into another seemingly pseudo random number
 * in the same range. Every input n bit input will generate a different
 * n bit output. This is called a Feistel network. */
function feistelNet(input, bits) {
    var mask = Math.pow(2, bits) - 1;
    var halfBits = bits/2;
    var halfMask = Math.pow(2, halfBits) - 1;
    var l = input & halfMask;
    var r = input >> halfBits;
    for (var i = 0; i < 5; i++) {
        var nl = r;
        var F = (((r * 19) + (r >> 1)) ^ r) & halfMask;
        r = l ^ F;
        l = nl;
    }
    return ((r << halfBits) | l) & mask;
}

/* Called once every millisecond (or as fast as your browser allows), sets many
 * pixels. */
function draw(killer) {
    var j;
    var bits = 2 * Math.ceil(Math.log2(screen_width * screen_height) / 2);
    var lastFrame = Math.pow(2, bits)

    /* Set many pixels per iteration otherwise it's too slow. */
    for (j = 0; j < (lastFrame / 200); j++) {
        if (frame >= lastFrame) {
            killer.end();
            break;
        }
	    var fn = feistelNet(frame, bits);
        var x = fn % screen_width;
        var y = Math.floor(fn / screen_width);
        if (x < screen_width && y < screen_height) {
            setPixel(x,y);
        }
        frame++;
    }
    ctx.putImageData(pixels, 0, 0);
}

init();

</script>
</body>
</html>
	<!DOCTYPE html>
	<html>
	<head><title>Javascript RT</title></head>
	<style>canvas {width: 1280px; height: 768px}</style>
	<body>

	<canvas id="framebuffer"></canvas>

	<script type="text/javascript">
	/* Fizzlefade using a Feistel network.
	* Copyright (C) 2017 Salvatore Sanfilippo <antirez@gmail.com>
	* This softare is released under the terms of the BSD two-clause license.
	* See http://fabiensanglard.net/fizzlefade/index.php for more info. */

	var ctx;
	var pixels;
	var screen_width = 3480;
	var screen_height = 2160;
	var frame = 0;

	/* Here is a very ugly thing that calms my laptop's fan */
	var timerKiller = {
	timer: null,
	ended: false,
	setTimer: function (newTimer) {
	timer = newTimer;
	if(ended) {
	clearInterval(timer);
	}
	},
	end: function () {
	if(timer != null) {
	clearInterval(timer);
	}
	ended = true;
	}
	};

	/* Create a context where we can easily write pixels. */
	function init() {
	fb = document.getElementById('framebuffer');
	fb.width = screen_width;
	fb.height = screen_height;
	ctx = fb.getContext('2d');
	pixels = ctx.createImageData(screen_width, screen_height);
	timerKiller.setTimer(setInterval(draw, 1, timerKiller));
	};

	/* Write a pixel, just set alpha and RGB channels. */
	function setPixel(x,y) {
	var offset = x4+y4*screen_width;

	pixels.data[offset+3] = 255;
	pixels.data[offset+0] = 255;
	pixels.data[offset+1] = 0;
	pixels.data[offset+2] = 0;
	}

	/* Transforms the n bit input into another seemingly pseudo random number
	* in the same range. Every input n bit input will generate a different
	* n bit output. This is called a Feistel network. */
	function feistelNet(input, bits) {
	var mask = Math.pow(2, bits) - 1;
	var halfBits = bits/2;
	var halfMask = Math.pow(2, halfBits) - 1;
	var l = input & halfMask;
	var r = input >> halfBits;
	for (var i = 0; i < 5; i++) {
	var nl = r;
	var F = (((r * 19) + (r >> 1)) ^ r) & halfMask;
	r = l ^ F;
	l = nl;
	}
	return ((r << halfBits) \| l) & mask;
	}

	/* Called once every millisecond (or as fast as your browser allows), sets many
	* pixels. */
	function draw(killer) {
	var j;
	var bits = 2 * Math.ceil(Math.log2(screen_width * screen_height) / 2);
	var lastFrame = Math.pow(2, bits)

	/* Set many pixels per iteration otherwise it's too slow. */
	for (j = 0; j < (lastFrame / 200); j++) {
	if (frame >= lastFrame) {
	killer.end();
	break;
	}
	var fn = feistelNet(frame, bits);
	var x = fn % screen_width;
	var y = Math.floor(fn / screen_width);
	if (x < screen_width && y < screen_height) {
	setPixel(x,y);
	}
	frame++;
	}
	ctx.putImageData(pixels, 0, 0);
	}

	init();

	</script>
	</body>
	</html>