Pygame - 有没有办法只在掩码中进行 blit 或更新

问题描述

在 pygame 中是否有任何方法可以在掩码内将某些内容 blit 到屏幕上.例如:如果您有一个掩码，除了左上角和全黑图像外，所有位都设置为 1，而不更改图像，您能否保持左上角(与掩码相同)清晰?只有更新掩码(而不是矩形)才会有帮助.

Is there any way in pygame to blit something to the screen inside a mask. Eg: if you had a mask where all the bits were set to 1 except for the topleft corner and a fully black image, without changing the image, could you keep the top left corner (same as the mask) clear? Only updating a mask (rather than a rect) would help to.

推荐答案

好吧，如果我正确理解你的问题，诀窍是 BLEND_RGBA_MULT 标志.

Ok, if I'm understanding your question properly, the trick is the BLEND_RGBA_MULT flag.

我决定亲自测试一下，因为我很好奇.我从这张图片开始:

I decided to test this for myself because I was curious. I started with this image:

我用白色制作了一张我想要显示的图像，并在我想要遮罩的地方制作了透明度.我什至给它设置了不同程度的透明度，看看我是否可以得到模糊遮罩.

I made an image with white where I wanted the image to show, and transparency where I wanted it masked. I even gave it varying levels of transparency to see if I could get fuzzy masking.

^^^ 您可能看不到图像，因为它是透明的白色，但它就在那里.您可以右键单击并下载它.

^^^ You probably can't see the image because it's white on transparent, but it's there. You can just right click and download it.

我加载了两张图片，确保使用了convert_alpha():

I loaded the two images, making sure to use convert_alpha():

background = pygame.image.load("leaves.png").convert_alpha()
mask = pygame.image.load("mask-fuzzy.png").convert_alpha()

然后为了遮罩图像，我复制了被遮罩的图像，

Then to mask the image, I made a copy of the image being masked,

masked = background.copy()

...我使用 BLEND_RGBA_MULT 将蒙版复制到这个副本上，

...I blitted the mask onto this copy using BLEND_RGBA_MULT,

masked.blit(mask, (0, 0), None, pygame.BLEND_RGBA_MULT)

...然后我把它画到了屏幕上.

...and I drew it to the screen.

display.blit(masked, (0, 0))

果然成功了:

这是我使用的完整代码.

Here's the complete code I used.

import pygame
from pygame.locals import *

pygame.init()
display = pygame.display.set_mode((320, 240))

background = pygame.image.load("leaves.png").convert_alpha()
mask = pygame.image.load("mask-fuzzy.png").convert_alpha()

running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
    # draw
    display.fill(Color(255, 0, 255))
    masked = background.copy()
    masked.blit(mask, (0, 0), None, pygame.BLEND_RGBA_MULT)
    display.blit(masked, (0, 0))
    pygame.display.flip()

如果您想要一个可变遮罩，您可以尝试手动编辑一个 Surface 并将其用作您的遮罩.

If you want a variable mask, you could try manually editing a Surface and using that as your mask.

以下是通过编辑表面生成蒙版的示例:

Here's an example of generating a mask by editing a Surface:

mask = pygame.Surface((320, 240), pygame.SRCALPHA)
for y in range(0, 240):
    for x in range(0, 320):
        if (x/16 + y/16) % 2 == 0:
            mask.set_at((x, y), Color("white"))

它产生了这个结果:

现在我想在游戏中使用它！

Now I want to use this in a game!

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