如何使用 PyGame 使文本或图像淡入淡出

Question

有人可以帮我解决这个问题吗？ :

我试着制作一个在用户屏幕上流畅显示的标题:

def image(name,x,y,u):
   screen.blit(name,(x,y))
   if u = 1
      pygame.display.update()

Window == 'main'
While windows = 'main':
   image(background,0,0)
   image(title, 640, 120)
   pygame.display.update()

但是文字突然出现，而且不是我想要的...

Answer 1

pygame.Surface.blit() already does what you want. It bends a surface to an other surface, depended on its alpha channel. All you have to do is to set the alpha channel by pygame.Surface.set_alpha():

image.set_alpha(min(1.0,alpha)*255)

写一个函数，"blends"一个表面到屏幕。在下面的函数BlendSurface中，参数alpha是范围[0, 1]中表面的不透明度值。 0.0 将生成一个完全透明（不可见）的表面。 1.0 会生成一个完全不透明的表面：

def BlendSurface(image, pos, alpha):
    image.set_alpha(min(1.0,alpha)*255)
    screen.blit(image, pos)

查看简单的演示程序：

import pygame
import pygame.font
pygame.init()

BLUE    = (  0,   0, 255)
YELLOW  = (255, 255,   0)

size = (800,600)
screen = pygame.display.set_mode(size)

def BlendSurface(image, pos, alpha):
    image.set_alpha(min(1.0,alpha)*255)
    screen.blit(blendImage, pos)

clock = pygame.time.Clock()

font = pygame.font.SysFont('Times New Roman', 100)
text = font.render('blend text', False, YELLOW)

i = 0
done = False
while not done:
    clock.tick(60)
    i += 1
    if i > 200:
        i = 0

    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            done = True

    screen.fill(BLUE)
    BlendSurface(text, (100, 100), i/200) 
    pygame.display.flip()

Answer 2

您想使用透明度，pygame 使用 three different types:

There are three types of transparency supported in pygame: colorkeys, surface alphas, and pixel alphas. Surface alphas can be mixed with colorkeys, but an image with per pixel alphas cannot use the other modes. Colorkey transparency makes a single color value transparent. Any pixels matching the colorkey will not be drawn. The surface alpha value is a single value that changes the transparency for the entire image. A surface alpha of 255 is opaque, and a value of 0 is completely transparent.

Per pixel alphas are different because they store a transparency value for every pixel. This allows for the most precise transparency effects, but it also the slowest. Per pixel alphas cannot be mixed with surface alpha and colorkeys.

所以让我们使用 colorkey 创建一个透明的 Surface 并将一些文本 blit 到它，然后使用表面 alpha 通过调用 set_alpha 和 Surface 创建淡入效果:

import pygame

def main():
    screen = pygame.display.set_mode((300, 100))
    FONT = pygame.font.SysFont(None, 64)
    text = FONT.render('Hello World', False, pygame.Color('darkorange'))
    surf = pygame.Surface(text.get_rect().size)
    surf.set_colorkey((1,1,1))
    surf.fill((1,1,1))
    surf.blit(text, (0, 0))
    clock = pygame.time.Clock()
    alpha = 0
    while True:
        for e in pygame.event.get():
            if e.type == pygame.QUIT:
                return

        alpha = (alpha + 1) % 256
        surf.set_alpha(alpha)
        
        screen.fill(pygame.Color('dodgerblue'))
        screen.blit(surf, (20, 20))
        clock.tick(120)
        print(alpha)
        pygame.display.update()

if __name__ == '__main__':
    pygame.init()
    main()

如何使用 PyGame 使文本或图像淡入淡出

How to fade in a text or an image with PyGame

python

pygame

pygame-surface

python-3.7