tryhtml5_canvas_getimagedata2 在线代码实例

 <img id="scream" src="/upload2/attachments/image/20161109/1478674768430227.jpg">
<canvas id="myCanvas" width="220" height="277" style="border:1px solid #d3d3d3;">
您的浏览器不支持 HTML5 canvas 标签。
</canvas>
<script>
document.getElementById("scream").onload=function(){
    var c=document.getElementById("myCanvas");     var ctx=c.getContext("2d");
    var img=document.getElementById("scream");
    ctx.drawImage(img,0,0);
    var imgData=ctx.getImageData(0,0,c.width,c.height);
    // 反转颜色
    for (var i=0;i<imgData.data.length;i+=4){
		imgData.data[i]=255-imgData.data[i];
		imgData.data[i+1]=255-imgData.data[i+1];
		imgData.data[i+2]=255-imgData.data[i+2];
		imgData.data[i+3]=255;
    }
	ctx.putImageData(imgData,0,0);
};
</script>