想用cropper裁剪图片后转为blob格式上传到服务器，却传不上去

[mango_beverge]

代码在下边……请各位大神帮忙看一下呀，小白菜跪求了
// 确定按钮点击事件
$("#sure").on("click", function() {
if ($("#img").attr("src") == null) {
return false;
} else {
$('#img').cropper('getCroppedCanvas').toBlob(function (blob) {
var formData = new FormData();
formData.append('croppedImage', blob);
$.ajax({
url :"/user/filesUpload",
method: "POST",
data: formData,
processData: false,
contentType: false,
success: function () {
alert("success");
console.log('Upload success');
},
error: function () {
console.log('Upload error');
}
});
}, "image/jpeg");
}
});