Question

I would like to draw lines (of arbitrary position and length) onto a surface in pygame, which itself is an image loaded from a file on disk.

Can anyone point me to some example code that does this?

Answer 1

This should do what you’re asking for:

# load the image image = pygame.image.load('some_image.png')  # draw a yellow line on the image pygame.draw.line(image, (255, 255, 0), (0, 0), (100, 100)) 

Typically you don’t draw to the original image, since you’ll have to reload the image to get the original back (or create a copy of it before you start drawing onto it). Perhaps what you actually need is something more like this:

# initialize pygame and screen import pygame pygame.init() screen = pygame.display.set_mode((720, 576))  # Draw the image to the screen screen.blit(image, (0, 0))  # Draw a line on top of the image on the screen pygame.draw.line(screen, (255, 255, 255), (0, 0), (50, 50))