How to fade in and out a text in Pygame

Question

I know how to show a text on screen, but I don't like the way it appears and disappears. I want it to fade in and out. Changing the RGB is impossible because there is a background image. Can you tell me a code which changes the text's opacity?

Answer 1

To fade out the text, you can blit a white, transparent surface onto the text surface and pass the pygame.BLEND_RGBA_MULT special flag.

Reduce (or increase to fade-in) the alpha value each frame or after a specific time interval (check out these timers) and use it to fill the alpha_surf:

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

Also, create a copy of the original text surface each time you change the alpha, otherwise it would fade-out too quickly because the original gets modified. Here's a minimal, complete example:

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()