html5 canvas线条下落动画特效

html5 canvas线条下落动画特效是一款跟下雨有点相似的线条下落动画效果。

(function(){

var c = document.getElementById("c"),
ctx = c.getContext("2d");

c.width = innerWidth;
c.height = innerHeight;

var lines = [],
maxSpeed = 5,
spacing = 5,
xSpacing = 0,
n = innerWidth / spacing,
colors = ["#3B8686", "#79BD9A", "#A8DBA8", "#0B486B"],
i;

for (i = 0; i < n; i++){
xSpacing += spacing;
lines.push({
x: xSpacing,
y: Math.round(Math.random()*c.height),
width: 2,
height: Math.round(Math.random()*(innerHeight/10)),
speed: Math.random()*maxSpeed + 1,
color: colors[Math.floor(Math.random() * colors.length)]
});
}


function draw(){
var i;
ctx.clearRect(0,0,c.width,c.height);

for (i = 0; i < n; i++){
ctx.fillStyle = lines[i].color;
ctx.fillRect(lines[i].x, lines[i].y, lines[i].width, lines[i].height);
lines[i].y += lines[i].speed;

if (lines[i].y > c.height)
lines[i].y = 0 - lines[i].height;
}

requestAnimationFrame(draw);

}

draw();

}());