androidFileReader读取图片资源显示预览失败解决方法

昨天用html5写一个手机上传图片问题，因为用户不可能自己剪辑图片，所以要在客户端生成缩图，不然用户没传两张把人家流量耗光了。

代码如下，

oImage.src="data:application/octet-stream;"+e.target.result.substr(e.target.result.indexOf("base64,"));

希望对有同样问题的同学有帮助，目前我使用

canvas.toDataURL("image/png");

function fileSelected() {    // hide different warnings    // get selected file element    var oFile = document.getElementById('image_file').files[0];    // filter for image files    var rFilter = /^(image\/bmp|image\/gif|image\/jpeg|image\/png|image\/tiff)$/i;    // little test for filesize showerror	sResultFileSize=oFile.size;    if (sResultFileSize > iMaxFilesize) {        return;    }    // get preview element    var oImage = document.getElementById('preview');    // prepare HTML5 FileReader	document.getElementById('showerror').innerHTML='正在读取文件。。。（要十多秒）请稍候';    var oReader = new FileReader();        oReader.Onload= function(e){	        oImage.src = e.target.result;				oImage.src="data:application/octet-stream;"+e.target.result.substr(e.target.result.indexOf("base64,"));	        oImage.Onload= function () { // binding onload event			//nshowerror').innerHTML='读取完成，请点上传按扭，有多张图片请继续上传';						fileup=false;        };		oImage.Onerror=function(){			document.getElementById('showerror').innerHTML='没有缩略图，请拍照或点上传按扭，有多张图片请继续上传';			fileup=true;		}    };    oReader.readAsDataURL(oFile);}function drawimg(oimg){    canvas = document.getElementById("myCanvas");                    canvas.width  = newwidth;                    canvas.height = newheight;    ctx = canvas.getContext('2d');ctx.drawImage(oimg, 0, 0, nwidth, nheight,0, 0, newwidth, newheight);pic=canvas.toDataURL("image/png");pic=pic.substr(22);}