$("#image").cropper('getCroppedCanvas').toBlob( function (blob){})

    /* Use binary method to process dataUrl */ 
    function processData(dataUrl) {
         var binaryString = window.atob(dataUrl.split(',')[1 ]);
         var arrayBuffer = new ArrayBuffer(binaryString.length);
         var intArray = new Uint8Array(arrayBuffer);
         for ( var i = 0, j = binaryString.length; i <j; i++ ) {
            intArray[i] = binaryString.charCodeAt(i);
        }

        var data = [intArray],
            blob;

        try {
            blob = new Blob(data);
        } catch (e) {
            window.BlobBuilder = window.BlobBuilder || 
                window.WebKitBlobBuilder || 
                window.MozBlobBuilder ||
                window.MSBlobBuilder;
            if (e.name ==='TypeError' && window.BlobBuilder) {
                 var builder = new BlobBuilder();
                builder.append(arrayBuffer);
                blob = builder.getBlob(imgType); // imgType is the upload file type, that is, file.type 
            } else {
                console.log( 'The version is too low to support uploading pictures' );
            }
        }
        return blob;
    }

    $('#cutBtn').click( function () {
         var data = $('#image').cropper('getCroppedCanvas' , {
                width: 300, // length and width after cropping 
                height: 300
            }),
            blob = processData(data.toDataURL());

        var formData = new FormData();
        formData.append( 'uploadImg' , blob);
        $.ajax({
            url: '/path/to/upload' ,
            method: "POST" ,
            data: formData,
            processData: false ,
            contentType: false ,
            success: function () {
                console.log( 'Upload success' );
            },
            error: function () {
                console.log( 'Upload error' );
            }
        });
    });