area.py

mask_img = np.array(Image.open(mask.file, mode='r').convert('1'))

# Absolute WSI coordinates
dx = max(patch_x, mask.x)
dx2 = min(patch_x + self.crop_size, mask.x + mask.width)
dy = max(patch_y, mask.y)
dy2 = min(patch_y + self.crop_size, mask.y + mask.height)

# Make the coordinates relative to the mask position
dx = dx - mask.x
dx2 = dx2 - mask.x
dy = dy - mask.y
dy2 = dy2 - mask.y

# Should get the union area between the patch and the mask
if dx2 > 0 and dy2 > 0:
  # Invert x and y because of PIL -> numpy transform
  area = mask_img[dy:dy2, dx:dx2]