pygame图像屏幕填充

Question

I have a pygame program that is meant to fill the pygame window with Grass.png:

import pygame, sys
from pygame.locals import *

pygame.init()

screen = pygame.display.set_mode([600, 500])

def DrawBackground(background, xpos, ypos):
    screen.blit(background, [xpos, ypos])

background = pygame.image.load('Grass.png')
xpos = 0
ypos = 0

while True:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            sys.exit()
    while ypos >= -500:
        while xpos <= 600:
            DrawBackground(background, xpos, ypos)
            xpos += 100
        ypos -= 100

    pygame.display.flip()

Only problem is, it only fills the first 100 pixel row with the image. What is wrong with the code? Thanks.

Answer 1

当您向下移动屏幕时，y轴为正-因此，当第一行的y位置为0时，下一行的y位置为100。基本上，您应该将y-坐标，而不是减法。

Answer 2

You're much better off using for loops rather than while loops to do that.

for y in range(5):
    for x in range(6):
        DrawBackground(background, x*100, y*100)

Makes the code much more readable and easier to debug. But in answer to your question, like frr171 said, the origin point (0, 0) is in the top left corner of the screen. As you go right, the x axis increases and as you go down the y axis increases.