@Override
    public LuminanceSource crop(int left, int top, int width, int height) {
        return new BufferedImageLuminanceSource(image, this.left + left, this.top + top, width, height);
    }
This LuminanceSource implementation is meant for J2SE clients and our blackbox unit tests.

@author dswitkin@google.com (Daniel Switkin)
@author Sean Owen
@author code@elektrowolle.de (Wolfgang Jung)
src/main/java/io/github/biezhi/wechat/utils/BufferedImageLuminanceSource.java