如何在 Pygame 中淡入淡出文本

Question

我知道如何在屏幕上显示文本，但我不喜欢它出现和消失的方式。我想让它淡入淡出。更改 RGB 是不可能的，因为有背景图像。你能告诉我一个改变文本不透明度的代码吗？

Answer 1

要使文本淡出，您可以将白色透明表面 blit 到文本表面并传递 pygame.BLEND_RGBA_MULT 特殊标志。

减少（或增加淡入）每帧或特定时间间隔后的 alpha 值（查看这些）并使用它来填充 alpha_surf：

alpha = max(alpha-4, 0)
alpha_surf.fill((255, 255, 255, alpha))

此外，每次更改 alpha 时都创建原始文本表面的副本，否则它会因为原始文本被修改而淡出得太快。这是一个最小的完整示例：

import pygame as pg


def main():
    clock = pg.time.Clock()
    screen = pg.display.set_mode((640, 480))
    font = pg.font.Font(None, 64)
    blue = pg.Color('royalblue')
    orig_surf = font.render('Enter your text', True, blue)
    txt_surf = orig_surf.copy()
    # This surface is used to adjust the alpha of the txt_surf.
    alpha_surf = pg.Surface(txt_surf.get_size(), pg.SRCALPHA)
    alpha = 255  # The current alpha value of the surface.

    while True:
        for event in pg.event.get():
            if event.type == pg.QUIT:
                return

        if alpha > 0:
            # Reduce alpha each frame, but make sure it doesn't get below 0.
            alpha = max(alpha-4, 0)
            txt_surf = orig_surf.copy()  # Don't modify the original text surf.
            # Fill alpha_surf with this color to set its alpha value.
            alpha_surf.fill((255, 255, 255, alpha))
            # To make the text surface transparent, blit the transparent
            # alpha_surf onto it with the BLEND_RGBA_MULT flag.
            txt_surf.blit(alpha_surf, (0, 0), special_flags=pg.BLEND_RGBA_MULT)

        screen.fill((30, 30, 30))
        screen.blit(txt_surf, (30, 60))
        pg.display.flip()
        clock.tick(30)


if __name__ == '__main__':
    pg.init()
    main()
    pg.quit()

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