Re: [pygame] Bug: numpyarray.pixels_alpha array not properly aligned

[Lenard Lindstrom <len-l@xxxxxxxxx>]

Marcus von Appen wrote:
> On, Tue Jan 08, 2008, Lenard Lindstrom wrote:
>
> [...] 
>   
> > The problem is that the major and minor axis of the array are reversed from 
> > those of the surface. Try replacing lines 272-276 with:
> >
> >    return numpy.ndarray(buffer=surface.get_buffer (),
> >                         dtype=numpy.uint8,
> >                         shape=surface.get_size (),
> >                         offset=start,
> >                         strides=(4, surface.get_pitch ()))
> >
> > The offset argument sets the relative position of the alpha byte. The 
> > strides argument makes the second argument the major axis and the first 
> > argument skip by the pixel size of 4 bytes. It works with the test case I 
> > submitted and an application I wrote that relies heavily on arrays. Hope 
> > this helps.
> >     
>
> You refer to rev. 1072 I guess, not to the fixed version? I cannot see
> any misbehaviour anymore.
>
>
>   

That was fast. Unfortunately I found more bugs. In surfarray.py lines 
241 and 243 should have "array" instead of "surface". Also make_surface 
ignores all but the blue color plane for a 3d array. I have enclosed a 
test program make_surface_bug.py.

Finally, I noticed a major performance decrease for array_colorkey on a 
24 bit surface with numpy. It runs 80 times slower than with Numeric. 
The attached array_colorkey.py is the benchmark program I used. 32 bits 
surfaces are only 5 times slower, so I suppose one can always update 
ones programs to them instead.

--
Lenard Lindstrom
<len-l@xxxxxxxxx>

# Shows bug with numpyarray.pixels_alpha.
# Displays two green rectangles with a transparent center.
# A surfarray.make_surface test for numpy. This show as an all-white window.

import pygame as pg
import numpy as np
import cPickle

pg.surfarray.use_array('numpy')

pg.init()

window_size = (200, 200)

screen = pg.display.set_mode(window_size)

pixels = np.zeros(window_size + (3,), np.uint8)
pixels[...] = 255  # All white.
s = pg.surfarray.make_surface(pixels)
screen.blit(s, (0, 0))

pg.display.flip()

while 1:
    event = pg.event.wait()
    if event.type in [pg.KEYDOWN, pg.QUIT]:
        break

# A program to compare compare the performance of surfarray.array_colorkey
# when using numpy and Numeric.

import pygame as pg
from time import clock

start = 0.0
numpy_elapse = 0.0
numeric_elapse = 0.0
a = None
s = pg.Surface((1000, 1000), 0, 24)
s.fill((255, 0, 0), (0, 0, 500, 1000))
s.fill((0, 255, 0), (500, 0, 500, 1000))
s.set_colorkey((0, 255, 0))

for i in range(40):
    pg.surfarray.use_array('numeric')
    start = clock()
    a = pg.surfarray.array_colorkey(s)
    numeric_elapse += clock() - start
    a = None

    pg.surfarray.use_array('numpy')
    start = clock()
    a = pg.surfarray.array_colorkey(s)
    numpy_elapse += clock() - start
    a = None

print "--- Results ---"
print "Numeric:", numeric_elapse, "seconds"
print "Numpy:", numpy_elapse, "seconds"