Image rotating in Pygame while keeping smooth edges

Question

I would like to rotate an image and also keep the edges smooth.

This is how it looks like

And after rotating

The code I'm using looks like

def rot_center(self, image, angle):
   """rotate an image while keeping its center and size"""
   orig_rect = image.get_rect()
   rot_image = pygame.transform.rotate(image, angle)
   rot_rect = orig_rect.copy()
   rot_rect.center = rot_image.get_rect().center
   rot_image = rot_image.subsurface(rot_rect).copy()
   return rot_image

Is there something I'm doing wrong?

Answer 1

Try using pygame.transform.rotozoom with a scale of 1. It says it's filtered, I think that means AA.

Answer 2

The problem with rotozoom is where the image's edges touch the rectangle and not all the outer parts, that means if you have a ship ,for instance, the recessed edges will look fine only the wider parts will have the aliasing problem. I managed to fix that by going to photoshop and scale in my PNG file by 2 pixels(depends on your image maybe you'll need to experiment with different scaling factors), this way i still have the same image's dimensions but the real image(the colored pixels) will not touch the image's rectangle while rotating.

Answer 3

Rotozoom doesn't seem to smooth the edges of a surface, though. That is, the inner part of the image will look nice, but the edge is still non-antialiased.