Converting pygame surface buffer bytes into numpy array

Question

Anybody know why this array I created from pygame's get_buffer method has the R, G, B, values reversed? I want to create an array with the colour values in the same order I put them in - like [8, 16, 32, 0]. Have I done something wrong or is this something with the way pygame stores pixel data?

>>> import pygame
>>> import pygame.gfxdraw
>>> import numpy as np
>>> background_colour = (1, 1, 1)
>>> width, height = (256, 256)
>>> screen = pygame.Surface((width, height))
>>> pygame.draw.rect(screen, (8, 16, 32), (0, 0, 100, 100), 0)
<rect(0, 0, 100, 100)>
>>> s = screen.get_buffer()
>>> x = np.fromstring(s.raw, dtype='b').reshape(height, width, 4)
>>> x[0, 0]
array([32, 16,  8,  0], dtype=int8)

I tried this but I loose the R value:

>>> y = x[:, :, 3:0:-1]
>>> y[0, 0]
array([ 0,  8, 16], dtype=int8)

(I'm using numpy version 1.8.2 so I don't have np.flip).

Bill · Accepted Answer · 2018-11-11 22:45:36Z

1

I realised there is a much better way to do this. The pygame.surfarray module has various methods that actually create numpy arrays for you!

>>> x3 = pygame.surfarray.pixels3d(screen)
>>> x3.shape
(256, 256, 3)
>>> x3[0, 0]
array([ 8, 16, 32], dtype=uint8)

answered Nov 11, 2018 at 22:45

Bill

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