How do you make an image transparent over a period of time?

Question

I am currently trying to display a death screen when the player dies in my game, but rather than it just popping up I want it to gradually becoming less and less transparent until the opacity is 256. I currently have this line of code below to display the image, but I was wondering how I would go about gradually increasing the opacity over a period of few seconds.

screen.blit(pygame.image.load("Images/dead.jpg"), (0, 0))

I've tried to add a for loop and tried to use convert_alpha, however I couldn't figure out a way of doing it, and any help will be greatly appreciated.

Answer 1

Here is what I would do. I have explained everything in the comments:

# Allow the image to have its alpha value changed
image = pygame.image.load("Images/dead.jpg").convert()

# Set the transparency to full
image_alpha = 0

# Decide how many frames you want the image to fade in over
fade_frame_number = 60
# And the frames per second
FPS = 30
FPS_Clock = pygame.time.Clock()

while True:
    window.fill((255, 255, 255))               # Fill the window with a white bg
    if image_alpha < 255:
        image_alpha += 255 / fade_frame_number # Change the transparency variable
    image.set_alpha(image_alpha)               # Set the image's alpha value
    window.blit(image, (0, 0))                 # Display the image
    pygame.display.update()                    # Update the screen
    FPS_Clock.tick(FPS)                        # Wait for the next frame

In this, window is the display surface.