canvas、image src、data url、blob file conversion

//canvas.toDataURL('image/jpeg'), and convert to blob,blob is a File Object. but UC don't support
function dataURLtoBlob(dataurl) {
    var arr = dataurl.split(','), mime = arr[0].match(/:(.*?);/)[1],
        bstr = atob(arr[1]), n = bstr.length, u8arr = new Uint8Array(n);
    while (n--) u8arr[n] = bstr.charCodeAt(n);
    window.BlobBuilder = window.BlobBuilder || window.WebKitBlobBuilder || window.MozBlobBuilder || window.MSBlobBuilder;
    if (window.BlobBuilder) {
        var bb = new BlobBuilder();
        bb.append([u8arr]);
        return bb.getBlob(mime);
    } else return new Blob([u8arr], { type: mime });
}

//html image src convert to dataUrl
function imageToDataURL(url, callback, mime) {
    var canvas = document.createElement('canvas'),
        ctx = canvas.getContext('2d'),
        img = new Image;
    img.crossOrigin = 'Anonymous';
    img.onload = function () {
        canvas.height = img.height;
        canvas.width = img.width;
        ctx.drawImage(img, 0, 0);
        var dataURL = canvas.toDataURL(mime || 'image/jpeg');
        callback.call(this, dataURL);
        canvas = null;
    };
    img.src = url;
}