在pygame中将图片添加到圆圈中

Question

我最近一直在努力将一个简单的 PNG 添加到 Pygame 中的一个圆圈中。出于某种原因，我得到的只是一个黑色的大方块，而不是一个里面有图片的圆圈：

import pygame
from pygame.locals import *
import math

planet_texture = pygame.image.load("earth.png")

"""  Initialize pygame """
pygame.init()

""" Define colors """
WHITE = (255, 255, 255)
BLACK = (0, 0, 0)
BLUE = (135, 206, 235)  # sky blue
YELLOW = (255, 255, 224)  # light yellow
RED = (255, 69, 0)  # red-orange

""" Define constants """
SCREEN_WIDTH = 800
SCREEN_HEIGHT = 600
PLANET_RADIUS = 100
ATMOSPHERE_THICKNESS = 70
LIGHT_SOURCE_RADIUS = 15
LIGHT_SOURCE_COLOR = WHITE
LIGHT_SOURCE_POS = (SCREEN_WIDTH // 4, SCREEN_HEIGHT // 2)

""" Create the screen """
screen = pygame.display.set_mode((SCREEN_WIDTH, SCREEN_HEIGHT))
pygame.display.set_caption("Rayleigh Scattering Simulation")

planet_texture.convert()

""" Main loop """
is_light_source_clicked = False

running = True
while running:
    for event in pygame.event.get():
        if event.type == QUIT:
            running = False
        elif event.type == MOUSEBUTTONDOWN and event.button == 1:
            # Check if the mouse is over the light source
            x, y = event.pos
            if math.sqrt((x - LIGHT_SOURCE_POS[0]) ** 2 + (y - LIGHT_SOURCE_POS[1]) ** 2) <= LIGHT_SOURCE_RADIUS:
                is_light_source_clicked = True
        elif event.type == MOUSEBUTTONUP and event.button == 1:
            is_light_source_clicked = False

    # Get the position of the mouse
    mouse_pos = pygame.mouse.get_pos()
    
    # Move the light source if it is clicked
    if is_light_source_clicked:
        LIGHT_SOURCE_POS = mouse_pos
        
    # clear the disaply
    screen.fill(0)
    
    # Create a new surface with the same size as the circle
    image_surface = pygame.Surface((PLANET_RADIUS * 2, PLANET_RADIUS * 2))
    
    # Get the rect of the image surface
    image_rect = planet_texture.get_rect()
    
    # Set the center of the image rect to the center of the circle
    image_rect.center = (SCREEN_WIDTH // 2, SCREEN_HEIGHT // 2)
    
    # Blit the planet texture onto the new surface
    image_surface.blit(planet_texture, (0, 0))
    
    # Scale the image to fit inside the circle
    scaled_image = pygame.transform.scale(image_surface, (PLANET_RADIUS * 2, PLANET_RADIUS * 2))
    
    # Create a rect for the scaled image and set its center to the center of the circle
    scaled_image_rect = scaled_image.get_rect()
    scaled_image_rect.center = (SCREEN_WIDTH // 2, SCREEN_HEIGHT // 2)
    
    # Draw the planet
    pygame.draw.circle(screen, BLACK, (SCREEN_WIDTH // 2, SCREEN_HEIGHT // 2), PLANET_RADIUS)

    # Draw the atmosphere
    for i in range(1, ATMOSPHERE_THICKNESS + 1):
        alpha = int((math.sin(math.pi * i / (2 * ATMOSPHERE_THICKNESS))) * 255)
        color = (BLUE[0], BLUE[1], BLUE[2], alpha)
        pygame.draw.circle(screen, color, (SCREEN_WIDTH // 2, SCREEN_HEIGHT // 2), PLANET_RADIUS + i, i)
    
    # Draw the light source
    pygame.draw.circle(screen, LIGHT_SOURCE_COLOR, LIGHT_SOURCE_POS, LIGHT_SOURCE_RADIUS)
    
    # Blit the scaled image onto the screen
    screen.blit(scaled_image, scaled_image_rect)
    
    # Update the screen
    pygame.display.update()

""" Quit pygame """
pygame.quit()

不知道是不是操作顺序问题，还是漏了一步。我还不完全熟悉 pygame 库。