module ChunkyPNG::Canvas::Adam7Interlacing

def adam7_extract_pass(pass, canvas)

Returns:
  • (ChunkyPNG::Canvas) - The extracted pass image.

Parameters:
  • canvas (ChunkyPNG::Canvas) -- The image that is being deconstructed.
  • pass (Integer) -- The pass number, should be in 0..6. 
def adam7_extract_pass(pass, canvas)
  x_shift, x_offset, y_shift, y_offset = adam7_multiplier_offset(pass)
  sm_pixels = []
  y_offset.step(canvas.height - 1, 1 << y_shift) do |y|
    x_offset.step(canvas.width - 1, 1 << x_shift) do |x|
      sm_pixels << canvas[x, y]
    end
  end
  new_canvas_args = adam7_pass_size(pass, canvas.width, canvas.height) + [sm_pixels]
  ChunkyPNG::Canvas.new(*new_canvas_args)
end