用JS实现渐变效果，兼容各款浏览器

以住做B/S的系统都是以IE浏览器为主，基本上忽略其他的浏览器，这次决定来个大兼容，但在实现背景渐变上就是个大麻烦。本想用图片来实现的，但 要兼顾多种分辨率实在不好办，最后在网上找到一个Javascript的实现办法，兼容IE6/7、FF、Safari等，相当完美。好东西不敢独占，贴 出来大家共享：

<SCRIPT>
var setGradient = (function(){
//private variables;
var p_dCanvas = document.createElement('canvas');
var p_useCanvas = !!( typeof(p_dCanvas.getContext) == 'function');
var p_dCtx = p_useCanvas?p_dCanvas.getContext('2d'):null;
var p_isIE = /*@cc_on!@*/false;

//test if toDataURL() is supported by Canvas since Safari may not support it
try{ p_dCtx.canvas.toDataURL() }
catch(err){ p_useCanvas = false; };

if(p_useCanvas){
return function (dEl , sColor1 , sColor2 , bRepeatY ){
if(typeof(dEl) == 'string') dEl = document.getElementById(dEl);
if(!dEl) return false;
var nW = dEl.offsetWidth;
var nH = dEl.offsetHeight;
p_dCanvas.width = nW;
p_dCanvas.height = nH;

var dGradient;
var sRepeat;
// Create gradients
if(bRepeatY){
dGradient = p_dCtx.createLinearGradient(0,0,nW,0);
sRepeat = 'repeat-y';
}else{
dGradient = p_dCtx.createLinearGradient(0,0,0,nH);
sRepeat = 'repeat-x';
}

dGradient.addColorStop(0,sColor1);
dGradient.addColorStop(1,sColor2);

p_dCtx.fillStyle = dGradient ;
p_dCtx.fillRect(0,0,nW,nH);
var sDataUrl = p_dCtx.canvas.toDataURL('image/png');

with(dEl.style){
backgroundRepeat = sRepeat;
backgroundImage = 'url(' + sDataUrl + ')';
backgroundColor = sColor2;
};
}
}else if(p_isIE){
p_dCanvas = p_useCanvas = p_dCtx = null;
return function (dEl , sColor1 , sColor2 , bRepeatY){
if(typeof(dEl) == 'string') dEl = document.getElementById(dEl);
if(!dEl) return false;
dEl.style.zoom = 1;
var sF = dEl.currentStyle.filter;
dEl.style.filter += ' ' + ['progid:DXImageTransform.Microsoft.gradient( GradientType=', +(!!bRepeatY),',enabled=true,startColorstr=',sColor1,', endColorstr=',sColor2,')'].join('');
};
}else{
p_dCanvas = p_useCanvas = p_dCtx = null;
return function(dEl , sColor1 , sColor2 ){
if(typeof(dEl) == 'string') dEl = document.getElementById(dEl);
if(!dEl) return false;
with(dEl.style){ backgroundColor = sColor2; };
//alert('your browser does not support gradient effet');
}
}
})();
</script>
//调用方式：
<script>
setGradient('example1','#4ddbbe','#d449cc',1);
setGradient(document.body, '#629be2','#333ebe',0);
</script>