Python Crash Course Alien Game - Replace background colour with background .bmp image

Question

I have a working Alien Invasion game which is from the Python Crash Course book. However, I am applying modifications. I am trying to replace the value of bg_color to represent a background image stored in my project folder instead of a colour i.e

self.bg_color = pygame.image.load('images/space.bmp')

Currently the AlienInvasion class imports the background colour from a class called settings stored in a sep file called settings.py

class Settings:
    """A class to store all settings for Alien Invasion."""
    def __init__(self):
        """Initialize the game's static settings."""
        # Screen settings
        self.screen_width = 1200
        self.screen_height = 800
        self.bg_color = (230,230,230)

AlienInvasion is the main game class which sets up the game.

class AlienInvasion:
    """Overall class to manage game assets and behavior."""
    def __init__(self):
        """Initialize the game, and create game resources."""
        pygame.init()
        """create a settings object using the imported settings class"""
        self.settings = Settings()
        """initialise the game display using the settings saved within the settings file"""
        self.screen = pygame.display.set_mode((self.settings.screen_width, self.settings.screen_height))
        """ assign the imported ship attributes to a new ship instance - "Self" in the call references to a call of AlienInvasion as a class """
        self.ship = Ship(self)
        """ run the game in full screen mode """
        pygame.display.set_caption("Alien Invasion")
        # Set the background color.
        self.bg_color = (230, 230, 230)

Update_screen updates the screen continually as the game progresses and handles the background colour when the game is run

def _update_screen(self):
            """Update the images on the screen and flip to the new screen"""  
            # Redraw the screen during each pass through the loop. Use the settings file here
            self.screen.fill(self.settings.bg_color)

I think my issue is to do with .fill() applying only to colour values (230, 230, 230). But I essentially want the screen to update with the background image rather than a static colour. Can somebody please assist? Is there another function I should be using instead of .fill()?

Answer 1

Change the background in Settings:

class Settings:
    def __init__(self):
        # [...]
    
        self.bg_color = pygame.image.load('images/space.bmp')

Get the background from the Settings object in the constructor of AlienInvasion. If the background image is a different size than the display, I recommend using pygame.transform.smoothscale() to scale the background to the correct size:

class AlienInvasion:
    """Overall class to manage game assets and behavior."""
    def __init__(self):
        # [...]
        self.settings = Settings()
        # [...]

        self.bg_color = pygame.transform.smoothscale(self.settings.bg_color, 
                            self.screen.get_size())
 

blit the background rather rather than fill the display surface:

class AlienInvasion:
    # [...]

    def _update_screen(self):
        self.screen.blit(self.settings.bg_color, (0, 0))

blit draw one image onto another. In this case it draw the background image (Surface) on the Surface which is associated to the display.

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Note, that the name bg_color is misleading. If you are using a background image, you should rename it (e.g. bg_image or bg_surface).