Thanks for gif cropperjs lib it helps me a lot in my project,
but I found an issue about rotated area crop.

after cropper.rotate(-45),
cropped blob area is not matched with canvas

I think this is cause of setupCanvas function's rotated box check

    var rotatedBoxWidth = (this.width*Math.cos(radian)+this.height*Math.sin(radian)) * limitRatio;
    var rotatedBoxHeight = (this.height*Math.cos(radian)+this.width*Math.sin(radian)) * limitRatio;

var rotatedBoxWidth = (this.widthMath.cos(radian)+this.heightMath.sin(radian)) * limitRatio;

利用OSS的图像处理.
实测阿里云支持对gif截取处理.

截图上传时,检测到gif时,不做canvas处理,获取到用户选择的坐标尺寸,然后直接上传原图到OSS,保存图片链接时,按照OSS的格式,将截图坐标附上即可

如
test.gif保存为test.gif?x-oss-process=image/crop,x_50,y_50,w_100,h_100