使用pygame.transform.rotate（）时出现奇怪的移位

Question

def rotate(self):
    #Save the original rect center
    self.saved_center=self.rect.center

    #Rotates a saved image every time to maintain quality
    self.image=pygame.transform.rotate(self.saved_image, self.angle)

    #Make new rect center the old one
    self.rect.center=self.saved_center

    self.angle+=10

When I rotate the image, there is a weird shifting of it despite the fact that I'm saving the old rect center and making the rotated rect center the old one. I want it to rotate right at the center of the square.

Here's what it looks like: http://i.imgur.com/g6Os9.gif

Answer 1

You are just calculating the new rect wrong. Try this:

def rotate(self):
    self.image=pygame.transform.rotate(self.saved_image, self.angle)
    self.rect = self.image.get_rect(center=self.rect.center)
    self.angle+=10

It tells the new rect to center itself around the original center (the center never changes here. Just keeps getting passed along).

The issue was that the self.rect was never being properly updated. You were only changing the center value. The entire rect changes as the image rotates because it grows and shrinks in size. So what you needed to do was completely set the new rect each time.

self.image.get_rect(center=self.rect.center)

This calculates a brand new rect, while basing it around the given center. The center is set on the rect before it calculate the positions. Thus, you get a rect that is properly centered around your point.

Answer 2

I had this issue. My method has a bit of a different purpose, but I solved it quite nicely.

import pygame, math

def draw_sprite(self, sprite, x, y, rot):
    #'sprite' is the loaded image file.
    #'x' and 'y' are coordinates.
    #'rot' is rotation in radians.

    #Creates a new 'rotated_sprite' that is a rotated variant of 'sprite'
    #Also performs a radian-to-degrees conversion on 'rot'.
    rotated_sprite = pygame.transform.rotate(sprite, math.degrees(rot))

    #Creates a new 'rect' based on 'rotated_sprite'
    rect = rotated_sprite.get_rect()

    #Blits the rotated_sprite onto the screen with an offset from 'rect'
    self.screen.blit(rotated_sprite, (x-(rect.width/2), y-(rect.height/2)))