canvas绘制动态背景

所属分类:背景类

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canvas绘制动态背景

一、本插件应用

前端资源库 头部的canvas自动变化的背景,就是引用了这个插件!这个用canvas绘制的自动变化的背景。


二、介绍

本下载demo中有七个案例,都是canvas绘制的。这里我简单的介绍一下第一个!


大家可以点击预览效果,看一下!


案例是全屏的。贴一下代码:



var w = c.width = window.innerWidth,
h = c.height = window.innerHeight,
ctx = c.getContext('2d'),
opts = {
	len: 20,
	count: 50,
	baseTime: 10,
	addedTime: 10,
	dieChance: .05,
	spawnChance: 1,
	sparkChance: .1,
	sparkDist: 10,
	sparkSize: 2,
	color: 'hsl(hue,100%,light%)',
	baseLight: 50,
	addedLight: 10,
	shadowToTimePropMult: 6,
	baseLightInputMultiplier: .01,
	addedLightInputMultiplier: .02,
	cx: w / 2,
	cy: h / 2,
	repaintAlpha: .04,
	hueChange: .1
},
tick = 0,
lines = [],
dieX = w / 2 / opts.len,
dieY = h / 2 / opts.len,
baseRad = Math.PI * 2 / 6;
ctx.fillStyle = '#2085c5';
ctx.fillRect(0, 0, w, h);
function loop() {
	window.requestAnimationFrame(loop); ++tick;
	ctx.globalCompositeOperation = 'source-over';
	ctx.shadowBlur = 0;
	ctx.fillStyle = 'rgba(43,94,200,alp)'.replace('alp', opts.repaintAlpha);
	ctx.fillRect(0, 0, w, h);
	ctx.globalCompositeOperation = 'lighter';
	if (lines.length < opts.count && Math.random() < opts.spawnChance) lines.push(new Line); lines.map(function(line) { line.step() }) } function Line() { this.reset() } Line.prototype.reset = function() { this.x = 0; this.y = 0; this.addedX = 0; this.addedY = 0; this.rad = 0; this.lightInputMultiplier = opts.baseLightInputMultiplier + opts.addedLightInputMultiplier * Math.random(); this.color = opts.color.replace('hue', tick * opts.hueChange); this.cumulativeTime = 0; this.beginPhase() } Line.prototype.beginPhase = function() { this.x += this.addedX; this.y += this.addedY; this.time = 0; this.targetTime = (opts.baseTime + opts.addedTime * Math.random()) | 0; this.rad += baseRad * (Math.random() < .5 ? 1 : -1); this.addedX = Math.cos(this.rad); this.addedY = Math.sin(this.rad); if (Math.random() < opts.dieChance || this.x > dieX || this.x < -dieX || this.y > dieY || this.y < -dieY) this.reset() } Line.prototype.step = function() {++this.time; ++this.cumulativeTime; if (this.time >= this.targetTime) this.beginPhase();
	var prop = this.time / this.targetTime,
	wave = Math.sin(prop * Math.PI / 2),
	x = this.addedX * wave,
	y = this.addedY * wave;
	ctx.shadowBlur = prop * opts.shadowToTimePropMult;
	ctx.fillStyle = ctx.shadowColor = this.color.replace('light', opts.baseLight + opts.addedLight * Math.sin(this.cumulativeTime * this.lightInputMultiplier));
	ctx.fillRect(opts.cx + (this.x + x) * opts.len, opts.cy + (this.y + y) * opts.len, 2, 2);
	if (Math.random() < opts.sparkChance) ctx.fillRect(opts.cx + (this.x + x) * opts.len + Math.random() * opts.sparkDist * (Math.random() < .5 ? 1 : -1) - opts.sparkSize / 2, opts.cy + (this.y + y) * opts.len + Math.random() * opts.sparkDist * (Math.random() < .5 ? 1 : -1) - opts.sparkSize / 2, opts.sparkSize, opts.sparkSize) } loop(); window.addEventListener('resize', function() { w = c.width = window.innerWidth; h = c.height = window.innerHeight; ctx.fillStyle = '#2085c5 '; ctx.fillRect(0, 0, w, h); opts.cx = w / 2; opts.cy = h / 2; dieX = w / 2 / opts.len; dieY = h / 2 / opts.len });



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