我需要一些关于画布和 HTML5 的帮助。
我有这个代码
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<title>HTML Canvas Flag Wave</title>
<style type="text/css" media="screen">
body { background:#eee }
#flag { position:absolute; top:50%; left:50% }
</style>
<script type="text/javascript">
var h = new Image;
h.onload = function(){
var flag = document.getElementById('flag');
var amp = 20;
flag.width = h.width;
flag.height = h.height + amp*2;
flag.getContext('2d').drawImage(h,0,amp,h.width,h.height);
flag.style.marginLeft = -(flag.width/2)+'px';
flag.style.marginTop = -(flag.height/2)+'px';
var timer = waveFlag( flag, h.width/10, amp );
};
h.src = 'gkhead.jpg';
function waveFlag( canvas, wavelength, amplitude, period, shading, squeeze ){
if (!squeeze) squeeze = 0;
if (!shading) shading = 100;
if (!period) period = 200;
if (!amplitude) amplitude = 10;
if (!wavelength) wavelength = canvas.width/10;
var fps = 30;
var ctx = canvas.getContext('2d');
var w = canvas.width, h = canvas.height;
var od = ctx.getImageData(0,0,w,h).data;
// var ct = 0, st=new Date;
return setInterval(function(){
var id = ctx.getImageData(0,0,w,h);
var d = id.data;
var now = (new Date)/period;
for (var y=0;y<h;++y){
var lastO=0,shade=0;
var sq = (y-h/2)*squeeze;
for (var x=0;x<w;++x){
var px = (y*w + x)*4;
var pct = x/w;
var o = Math.sin(x/wavelength-now)*amplitude*pct;
var y2 = y + (o+sq*pct)<<0;
var opx = (y2*w + x)*4;
shade = (o-lastO)*shading;
d[px ] = od[opx ]+shade;
d[px+1] = od[opx+1]+shade;
d[px+2] = od[opx+2]+shade;
d[px+3] = od[opx+3];
lastO = o;
}
}
ctx.putImageData(id,0,0);
// if ((++ct)%100 == 0) console.log( 1000 * ct / (new Date - st));
},1000/fps);
}
</script>
</head>
<body>
<canvas id="flag"></canvas>
</body>
</html>结果是这样的： http ://www.americkiplakari.org/zastavanovo.html
漂亮的挥舞旗帜，但我有一个问题，我不太擅长画布。我想旋转画布，我想固定图像的顶部并且波浪从上到下，是否可以这样做。