Why Is Surface.unlock Failing To Unlock The Surface For Blitting?

I'm trying to apply a numpy array of alpha values to a surface. I'm able to do so, but the surface remains locked after this operation such that I cannot blit the surface to my di

Solution 1:

Make a sprite class and put the values in an update function. This way, the array will be created and destroyed within the scope of the function. Here's an example in which you can make the grey block transparent by pressing the space bar:

import pygame
from pygame.locals import QUIT, KEYDOWN, K_ESCAPE, K_SPACE, SRCALPHA


class Game(object):
    def __init__(self):
        pygame.init()
        self.width, self.height = 800, 800
        pygame.display.set_caption("Surfarray test")
        self.screen = pygame.display.set_mode((self.width, self.height))
        self.background = pygame.Surface((self.width, self.height))
        self.background.fill((255, 255, 255))
        self.background.convert()
        self.bar = pygame.Surface((200, 100))
        self.bar.fill((255, 0, 0))
        self.bar.convert()

        self.sprite = pygame.sprite.GroupSingle()
        self.sprite.add(CustomSprite(pygame.Rect(5, 5, 100, 100)))

    def input(self):
        for event in pygame.event.get():

            if event.type == QUIT:
                return False

            if event.type == KEYDOWN:
                if event.key == K_ESCAPE:
                    return False
                if event.key == K_SPACE:
                    # make bar transparent by pressing the space bar
                    self.sprite.update()

    def main(self):
        while True:
            if self.input() is False:
                return False
            self.draw()

    def draw(self):
        self.screen.blit(self.background, (0, 0))
        self.screen.blit(self.bar, (5, 5))
        self.sprite.draw(self.screen)
        pygame.display.update()


class CustomSprite(pygame.sprite.Sprite):
    def __init__(self, rect):
        pygame.sprite.Sprite.__init__(self)
        self.rect = rect
        # SRCALPHA flag makes the pixel format include per-pixel alpha data
        self.image = pygame.Surface((rect.width, rect.height), SRCALPHA)
        self.image.convert_alpha()
        self.image.fill((126, 126, 126))

    # magic happens here
    def update(self):
        pxa = pygame.surfarray.pixels_alpha(self.image)
        pxa[:] = 100  # make all pixels transparent

if __name__ == "__main__":
    game = Game()
    game.main()