python - 如何在 PyGame 中滚动背景表面？

Question

我正在尝试在基于 pyGame 的随机 map 生成器中设置滚动。但是，我无法弄清楚如何防止显示“涂抹”背景，而不是仅仅滚动背景。我专门为 Stack Overflow 制作了一个 MCV 示例，仅显示彩色方 block 。也有同样的问题。

如何让显示滚动而不弄脏屏幕？

这是 map 生成器在我滚动一下后显示的内容:

MCV 示例:

""" This example just displays colored squares. """

import pygame
import sys


def main():

    pygame.init()

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

    x_pos = 0
    y_pos = 0
    yellow = (255, 255, 0)
    blue = (0, 0, 255)

    # draw pattern of yellow and blue squares
    for y in range(100):
        for x in range(100):

            if (y + x) % 2 == 0:
                pygame.draw.rect(screen, yellow, (x_pos, y_pos, 50, 50))
            else:
                pygame.draw.rect(screen, blue, (x_pos, y_pos, 50, 50))

            x_pos += 50

        y_pos += 50
        x_pos = 0

    while True:  # <-- the pyGame loop

        event = pygame.event.poll()
        pressed = pygame.key.get_pressed()

        # handle window closing
        if event.type == pygame.QUIT:
            break

        # handle scrolling
        if pressed[pygame.K_UP]:
            screen.scroll(0, 2)
        elif pressed[pygame.K_DOWN]:
            screen.scroll(0, -2)
        elif pressed[pygame.K_LEFT]:
            screen.scroll(2, 0)
        elif pressed[pygame.K_RIGHT]:
            screen.scroll(-2, 0)

        # updates what the window displays
        pygame.display.update()

    pygame.quit()
    sys.exit(0)


if __name__ == "__main__":
    # runs the pyGame loop
    main()

初始 MCVE 图像

滚动后MCVE显示:

Answer 1

pygame.Surface.scroll()没有达到您的预期。它不会无缝滚动表面。请参阅文档:

scroll() Shift the surface image in place

[...] Areas of the surface that are not overwritten retain their original pixel values. [...]

您必须编写自己的滚动函数，将表面移出的部分放置在表面的另一侧。

例如编写 2 个函数(scrollX 和 scrollY)，它们可以沿轴滚动:

def scrollX(screenSurf, offsetX):
    width, height = screenSurf.get_size()
    copySurf = screenSurf.copy()
    screenSurf.blit(copySurf, (offsetX, 0))
    if offsetX < 0:
        screenSurf.blit(copySurf, (width + offsetX, 0), (0, 0, -offsetX, height))
    else:
        screenSurf.blit(copySurf, (0, 0), (width - offsetX, 0, offsetX, height))

def scrollY(screenSurf, offsetY):
    width, height = screenSurf.get_size()
    copySurf = screenSurf.copy()
    screenSurf.blit(copySurf, (0, offsetY))
    if offsetY < 0:
        screenSurf.blit(copySurf, (0, height + offsetY), (0, 0, width, -offsetY))
    else:
        screenSurf.blit(copySurf, (0, 0), (0, height - offsetY, width, offsetY))

if pressed[pygame.K_UP]:
    scrollY(screen, 2)
elif pressed[pygame.K_DOWN]:
    scrollY(screen, -2)
elif pressed[pygame.K_LEFT]:
    scrollX(screen, 2)
elif pressed[pygame.K_RIGHT]:
    scrollX(screen, -2)