我想围绕一个枢轴旋转图像，该枢轴不在图像的中心Surface https://www.pygame.org/docs/ref/surface.html in Pygame https://www.pygame.org/news.
枢轴是图像中的绿色十字：
我知道游戏窗口中枢轴的位置。 如何跟踪此时的图像并同时围绕该点旋转它。
image = pygame.image.load("boomerang64.png")
pos = (200, 200)
angle = 0
while True:
# [...]
rotate_rect, rotate_image = ???? # rotate around green cross by angle
surf.blit(rotated_image, rotate_rect)
angle += 1
# [...]
首先是枢轴的位置Surface必须定义：
image = pygame.image.load("boomerang64.png") # 64x64 surface
pivot = (48, 21) # position of the pivot on the image
当图像旋转时，其尺寸会增加。我们必须比较轴对齐边界框 https://en.wikipedia.org/wiki/Minimum_bounding_box旋转前和旋转后的图像。
对于下面的数学pygame.math.Vector2 https://www.pygame.org/docs/ref/math.html用来。请注意，在屏幕坐标中，y 指向屏幕下方，但数学上的 y 轴点从底部到顶部。这导致在计算过程中必须“翻转”y 轴。请注意pygame.math.Vector2.rotate沿相反方向旋转pygame.transform.rotate。因此必须反转角度。
设置一个包含边界框 4 个角点的列表，并将向量旋转到角点pygame.math.Vector2.rotate https://www.pygame.org/docs/ref/math.html#pygame.math.Vector2.rotate。最后找到旋转框的最小值。由于 pygame 中的 y 轴指向下方，因此必须通过找到旋转反转高度的最大值（“最大（旋转（-h））"):
计算从图像中心到枢轴的向量：
image_rect = image.get_rect(topleft = (pos[0] - originPos[0], pos[1]-originPos[1]))
offset_center_to_pivot = pygame.math.Vector2(pos) - image_rect.center
旋转偏移向量：
rotated_offset = offset_center_to_pivot.rotate(-angle)
计算旋转图像的中心：
rotated_image_center = (pos[0] - rotated_offset.x, pos[1] - rotated_offset.y)
旋转并位图传输图像：
rotated_image = pygame.transform.rotate(image, angle)
rotated_image_rect = rotated_image.get_rect(center = rotated_image_center)
screen.blit(rotated_image, rotated_image_rect)
在下面的示例程序中，函数blitRotate(surf, image, pos, originPos, angle)执行上述所有步骤并且blit https://www.pygame.org/docs/ref/surface.html#pygame.Surface.blit旋转图像到与显示器关联的 Surface：
surf是目标表面image是必须旋转的表面并且blit
pos是目标表面上枢轴的位置surf（相对于左上角surf)originPos是枢轴在image表面（相对于左上角image)angle是以度为单位的旋转角度import math
import pygame
def blitRotate(surf, image, pos, originPos, angle):
image_rect = image.get_rect(topleft = (pos[0] - originPos[0], pos[1]-originPos[1]))
offset_center_to_pivot = pygame.math.Vector2(pos) - image_rect.center
rotated_offset = offset_center_to_pivot.rotate(-angle)
rotated_image_center = (pos[0] - rotated_offset.x, pos[1] - rotated_offset.y)
rotated_image = pygame.transform.rotate(image, angle)
rotated_image_rect = rotated_image.get_rect(center = rotated_image_center)
surf.blit(rotated_image, rotated_image_rect)
pygame.init()
size = (400,400)
screen = pygame.display.set_mode(size)
clock = pygame.time.Clock()
image = pygame.image.load('Boomerang64.png')
pivot = (48, 21)
angle, frame = 0, 0
done = False
while not done:
clock.tick(60)
for event in pygame.event.get():
if event.type == pygame.QUIT:
done = True
screen.fill(0)
pos = (200 + math.cos(frame * 0.05)*100, 200 + math.sin(frame * 0.05)*50)
blitRotate(screen, image, pos, pivot, angle)
pygame.draw.line(screen, (0, 255, 0), (pos[0]-20, pos[1]), (pos[0]+20, pos[1]), 3)
pygame.draw.line(screen, (0, 255, 0), (pos[0], pos[1]-20), (pos[0], pos[1]+20), 3)
pygame.draw.circle(screen, (0, 255, 0), pos, 7, 0)
pygame.display.flip()
frame += 1
angle += 10
pygame.quit()
exit()
相同的算法可用于Sprite https://www.pygame.org/docs/ref/sprite.html#pygame.sprite.Sprite, too.
在这种情况下，位置（self.pos), 枢轴 (self.pivot）和角度（self.angle) 是类的实例属性。
在里面update方法self.rect and self.image计算属性。
Minimal example: 
repl.it/@Rabbid76/PyGame-RotateSpriteAroundOffCenterPivot
import math
import pygame
class SpriteRotate(pygame.sprite.Sprite):
def __init__(self, imageName, origin, pivot):
super().__init__()
self.image = pygame.image.load(imageName)
self.original_image = self.image
self.rect = self.image.get_rect(topleft = (origin[0]-pivot[0], origin[1]-pivot[1]))
self.origin = origin
self.pivot = pivot
self.angle = 0
def update(self):
# offset from pivot to center
image_rect = self.original_image.get_rect(topleft = (self.origin[0] - self.pivot[0], self.origin[1]-self.pivot[1]))
offset_center_to_pivot = pygame.math.Vector2(self.origin) - image_rect.center
# roatated offset from pivot to center
rotated_offset = offset_center_to_pivot.rotate(-self.angle)
# roatetd image center
rotated_image_center = (self.pos[0] - rotated_offset.x, self.pos[1] - rotated_offset.y)
# get a rotated image
self.image = pygame.transform.rotate(self.original_image, self.angle)
self.rect = self.image.get_rect(center = rotated_image_center)
self.angle += 10
pygame.init()
size = (400,400)
screen = pygame.display.set_mode(size)
clock = pygame.time.Clock()
boomerang = SpriteRotate('Boomerang64.png', (200, 200), (48, 21))
all_sprites = pygame.sprite.Group(boomerang)
frame = 0
done = False
while not done:
clock.tick(60)
for event in pygame.event.get():
if event.type == pygame.QUIT:
done = True
pos = (200 + math.cos(frame * 0.05)*100, 200 + math.sin(frame * 0.05)*50)
boomerang.pos = pos
all_sprites.update()
screen.fill(0)
all_sprites.draw(screen)
#pygame.draw.line(screen, (0, 255, 0), (pos[0]-20, pos[1]), (pos[0]+20, pos[1]), 3)
#pygame.draw.line(screen, (0, 255, 0), (pos[0], pos[1]-20), (pos[0], pos[1]+20), 3)
#pygame.draw.circle(screen, (0, 255, 0), pos, 7, 0)
pygame.display.flip()
frame += 1
pygame.quit()
exit()
如何使用 Pygame 围绕图像中心旋转图像？ https://stackoverflow.com/questions/4183208/how-do-i-rotate-an-image-around-its-center-using-pygame
如何在图像尺寸变大时绕其中心旋转图像（在 Pygame 中） https://stackoverflow.com/questions/54462645/how-to-rotate-an-image-around-its-center-while-its-scale-is-getting-largerin-py