search_color @ pygame.transform.threshold ignores alpha channel

[Kyuchumimo]

Current behavior:

search_color @ pygame.transform.threshold ignores alpha channel

Expected behavior:

I was expecting half image turn blue.

Screenshots

128x128 red image with one half 92 transparency and the other half 128 transparency:

after applying pygame.transform.threshold both regions turn blue with 128 transparency:

Test code

import pygame
pygame.init()

image = pygame.image.load('test.png')
pygame.transform.threshold(image, image, (255,0,0,92), (0,0,0,0), (0,0,255,128), 1, None, True)
pygame.image.save(image, 'test2.png')

pygame.quit()

[Starbuck5]

Hey @Kyuchumimo ! Thank you for the report.

We will probably not be able to change this for the sake of backwards compatibility. Maybe a pygame-ce 3 thing, or we could do a consider_alpha parameter like one of the other transform methods has now.

If your use case is truly a replace with a distance of 0, it looks like Pixelarray.replace accidentally supports that.

image = pygame.image.load('test.png')

px = pygame.PixelArray(image)
px.replace((255,0,0,92), (0,0,255,128))
px.close()

#pygame.transform.threshold(image, image, (255,0,0,92), (0,0,0,0), (0,0,255,128), 1, None, True)
pygame.image.save(image, 'test2.png')

[Starbuck5]

I think the best thing to do right now would be to add a note to the docs about this. Is that something you could take on?