var setGradient = (function(){
    //private variables;
    var p_dCanvas = document.createElement('canvas');
    var p_useCanvas =  (typeof(p_dCanvas.getContext) == 'function');
    //如果是IE则为null
    var p_dCtx = p_useCanvas?p_dCanvas.getContext('2d'):null;
    //cc_on 这个东西加上他两边的东西是有用的，但是不知道是干什么用的
    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');
            }
        }
    }
)();