//data为文件的base64编码
function dataURLtoBlob(data) {
    var tmp = data.split(',');
    tmp[1] = tmp[1].replace(//s/g,'');
    var binary = atob(tmp[1]);
    var array = [];
    for(var i = 0; i < binary.length; i++) {
        array.push(binary.charCodeAt(i));
    }
    return new Blob([new Uint8Array(array)], {type: 'image/jpeg'});
}