HTML5实践-灰色图片画廊实现的方法

<script src="jquery.min.js" type="text/javascript"></script><script type="text/javascript">        // 设置 window load事件是为了等待所有图片加载完毕之后才行运行    $(window).load(function(){                // 使图片渐入，这样有颜色的原图就不会显示出来了，然后再执行window load 事件        $(".item img").fadeIn(500);                // 复制图片        $(&#39;.item img&#39;).each(function(){                    var el = $(this);            el.css({"position":"absolute"}).wrap("<p class=&#39;img_wrapper&#39;             style=&#39;display: inline-block&#39;>").clone().addClass(&#39;img_grayscale&#39;)            .css({"position":"absolute","z-index":"998","opacity":"0"}).insertBefore(el).queue(function(){                            var el = $(this);                el.parent().css({"width":this.width,"height":this.height});                el.dequeue();            });                        this.src = grayscale(this.src);        });                // 使图片渐入         $(&#39;.item img&#39;).mouseover(function(){            $(this).parent().find(&#39;img:first&#39;).stop().animate({opacity:1}, 1000);        })        $(&#39;.img_grayscale&#39;).mouseout(function(){            $(this).stop().animate({opacity:0}, 1000);        });            });        // 使用canvas制作灰色图片    function grayscale(src){            var canvas = document.createElement(&#39;canvas&#39;);            var ctx = canvas.getContext(&#39;2d&#39;);            var imgObj = new Image();        imgObj.src = src;        canvas.width = imgObj.width;        canvas.height = imgObj.height;         ctx.drawImage(imgObj, 0, 0);         var imgPixels = ctx.getImageData(0, 0, canvas.width, canvas.height);                for(var y = 0; y < imgPixels.height; y++){                    for(var x = 0; x < imgPixels.width; x++){                        var i = (y * 4) * imgPixels.width + x * 4;                        var avg = (imgPixels.data[i] + imgPixels.data[i + 1] + imgPixels.data[i + 2]) / 3;                imgPixels.data[i] = avg;                 imgPixels.data[i + 1] = avg;                 imgPixels.data[i + 2] = avg;            }        }        ctx.putImageData(imgPixels, 0, 0, 0, 0, imgPixels.width, imgPixels.height);                return canvas.toDataURL();    }        </script>