如何在 pygame 中制作圆形表面

Question

我需要创建一个有边界圆的表面。在该表面上绘制的任何内容都不应在该边界圆之外可见。我试过使用遮罩、次表面、srcalpha 等，但似乎没有任何效果。

我的尝试：

w = ss.get_width  ()
h = ss.get_height ()    
    
TRANSPARENT = (255, 255, 255,   0)
OPAQUE      = (  0,   0,   0, 225)
    
crop = pygame.Surface ((w, h), pygame.SRCALPHA, ss)
crop.fill (TRANSPARENT)
    
c = round (w / 2), round (h / 2)
r = 1
pygame.gfxdraw.     aacircle (crop, *c, r, OPAQUE)
pygame.gfxdraw.filled_circle (crop, *c, r, OPAQUE)
    
ss = crop.subsurface (crop.get_rect ())
App.set_subsurface (self, ss)

稍后...

self.ss.fill (BLACK)
self.ss.blit (self.background, ORIGIN)

背景是方形图片。它应该被裁剪成圆形并呈现在屏幕上

基于 Rabbid76 笔记的解决方案：

def draw_scene (self, temp=None):
        if temp is None: temp = self.ss
        # 1. Draw everything on a surface with the same size as the window (background and scene).
        size = temp.get_size ()
        temp = pygame.Surface (size)
        self.draw_cropped_scene (temp)

        # 2. create the surface with the white circle.      
        self.cropped_background = pygame.Surface (size, pygame.SRCALPHA)
        self.crop ()

        # 3. blit the former surface on the white circle.
        self.cropped_background.blit (temp, ORIGIN, special_flags=pygame.BLEND_RGBA_MIN)
    
        # 4. blit the whole thing on the window.
        self.ss.blit (self.cropped_background, ORIGIN)

    def draw_cropped_scene (self, temp): App.draw_scene (self, temp)

crop() 的示例实现是：

def crop (self):
        o, bounds = self.bounds
        bounds = tr (bounds) # round elements of tuple
        pygame.gfxdraw.     aaellipse (self.cropped_background, *bounds, *bounds, OPAQUE)
        pygame.gfxdraw.filled_ellipse (self.cropped_background, *bounds, *bounds, OPAQUE)

Answer 1

The background is a square image. It should be cropped into the shape of a circle and rendered on screen

您可以使用混合模式 BLEND_RGBA_MIN 实现此目的（参见 pygame.Surface.blit）。

创建一个与 self.background 大小相同的透明 pygame.Surface。在 Surface 中间画一个白色圆圈，然后使用混合模式 BLEND_RGBA_MIN 在 Surface 上混合背景。最后你可以 blit 它在屏幕上：

size = self.background.get_size()
self.cropped_background = pygame.Surface(size, pygame.SRCALPHA)
pygame.draw.ellipse(self.cropped_background, (255, 255, 255, 255), (0, 0, *size))
self.cropped_background.blit(self.background, (0, 0), special_flags=pygame.BLEND_RGBA_MIN)

self.ss.fill(BLACK)
self.ss.blit(self.cropped_background, ORIGIN)

最小示例： repl.it/@Rabbid76/PyGame-ClipCircularRegion-1

import pygame
pygame.init()
window = pygame.display.set_mode((250, 250))

background = pygame.Surface(window.get_size())
for x in range(5):
    for y in range(5):
        color = (255, 255, 255) if (x+y) % 2 == 0 else (255, 0, 0)
        pygame.draw.rect(background, color, (x*50, y*50, 50, 50))

size = background.get_size()
cropped_background = pygame.Surface(size, pygame.SRCALPHA)
pygame.draw.ellipse(cropped_background, (255, 255, 255, 255), (0, 0, *size))
cropped_background.blit(background, (0, 0), special_flags=pygame.BLEND_RGBA_MIN)

run = True
while run:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            run = False
        
    window.fill(0)
    window.blit(cropped_background, (0, 0))
    pygame.display.flip()

另见 How to fill only certain circular parts of the window in pygame?

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