How can i rotate an image from the center rather than the corner in pygame? [duplicate]

Question

I am creating a game and i need to rotate the ship, how can i rotate the ship from the center rather than the top left corner? I am using python 2.7 and Pygame 1.9.

Here is the code that i already have to rotate the image.

shipImg = pygame.transform.rotate(shipImg,-90)

However this rotates the image from the corner.

Answer 1

Rotate the sprite then set the center of the new rect to the center of the old rect. This way the new one has the same center when you're done, making it look like it rotated around the center.

Here's an example function from the pygame wiki:

def rot_center(image, rect, angle):
    """rotate an image while keeping its center"""
    rot_image = pygame.transform.rotate(image, angle)
    rot_rect = rot_image.get_rect(center=rect.center)
    return rot_image,rot_rect

And here's how you would use it in your example:

# Draw ship image centered around 100, 100
oldRect = shipImg.get_rect(center=(100,100)) 
screen.blit(shipImg, oldRect) 

# Now  rotate the ship and draw it with the new rect, 
# which will keep it centered around 100,100
shipImg, newRect = rot_center(shipImg,oldRect,-90)
screen.blit(shipImg, newRect)