code: def masked_grid_1d_index_to_2d_pixel_index_from_mask(mask):
      
  
      total_regular_pixels = total_regular_pixels_from_mask(mask)
      grid_to_pixel = np.zeros(shape=(total_regular_pixels, 2))
      pixel_count = 0
  
      for y in range(mask.shape[0]):
          for x in range(mask.shape[1]):
              if not mask[y, x]:
                  grid_to_pixel[pixel_count, :] = y, x
                  pixel_count += 1
  
      return grid_to_pixel
docs: Compute a 1D array that maps every unmasked pixel to its corresponding 2d pixel using its (y,x) pixel indexes.
  
      For howtolens if pixel [2,5] corresponds to the second pixel on the 1D array, grid_to_pixel[1] = [2,5]