code: public BinaryBitmap crop(int left, int top, int width, int height) {
      LuminanceSource newSource = binarizer.getLuminanceSource().crop(left, top, width, height);
      return new BinaryBitmap(binarizer.createBinarizer(newSource));
    }
docs: Returns a new object with cropped image data. Implementations may keep a reference to the
  original data rather than a copy. Only callable if isCropSupported() is true.
  
  @param left The left coordinate, which must be in [0,getWidth())
  @param top The top coordinate, which must be in [0,getHeight())
  @param width The width of the rectangle to crop.
  @param height The height of the rectangle to crop.
  @return A cropped version of this object.