[英]How to rotate an image around its center while its scale is getting larger(in Pygame)
[英]How do I rotate an image around its center using Pygame?
我一直在嘗試使用pygame.transform.rotate()
圍繞其中心旋轉圖像,但它不起作用。 具體來說,掛起的部分是rot_image = rot_image.subsurface(rot_rect).copy()
。 我得到了例外:
ValueError: subsurface rectangle outside surface area
這是用於旋轉圖像的代碼:
def rot_center(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
簡短的回答:
獲取原始圖像的矩形並設置位置。 獲取旋轉圖像的矩形,並通過原始矩形的中心設置中心位置。 返回旋轉圖像和矩形的元組:
def rot_center(image, angle, x, y):
rotated_image = pygame.transform.rotate(image, angle)
new_rect = rotated_image.get_rect(center = image.get_rect(center = (x, y)).center)
return rotated_image, new_rect
或者編寫一個旋轉和.blit
圖像的函數:
def blitRotateCenter(surf, image, topleft, angle):
rotated_image = pygame.transform.rotate(image, angle)
new_rect = rotated_image.get_rect(center = image.get_rect(topleft = topleft).center)
surf.blit(rotated_image, new_rect)
長答案:
圖像( pygame.Surface
)可以通過pygame.transform.rotate
旋轉。
如果在循環中逐步完成,則圖像會失真並迅速增加:
while not done:
# [...]
image = pygame.transform.rotate(image, 1)
screen.blit(image, pos)
pygame.display.flip()
這是因為旋轉圖像的邊界矩形總是大於原始圖像的邊界矩形(除了一些旋轉 90 度的倍數)。
由於多重副本,圖像會變形。 每次旋轉都會產生一個小錯誤(不准確)。 錯誤的總和在增加,圖像在衰減。
這可以通過保持原始圖像和“blit”由單個旋轉操作生成的圖像形成原始圖像來解決。
angle = 0
while not done:
# [...]
rotated_image = pygame.transform.rotate(image, angle)
angle += 1
screen.blit(rotated_image, pos)
pygame.display.flip()
現在圖像似乎可以隨意改變它的位置,因為圖像的大小會隨着旋轉而改變,並且原點始終是圖像邊界矩形的左上角。
這可以通過比較旋轉前后圖像的軸對齊邊界框來補償。
對於以下數學,使用pygame.math.Vector2
。 請注意屏幕坐標中的 y 指向屏幕下方,但數學上的 y 軸點從底部到頂部形成。 這導致在計算期間必須“翻轉”y軸
用邊界框的 4 個角點建立一個列表:
w, h = image.get_size()
box = [pygame.math.Vector2(p) for p in [(0, 0), (w, 0), (w, -h), (0, -h)]]
通過pygame.math.Vector2.rotate
將向量旋轉到角點:
box_rotate = [p.rotate(angle) for p in box]
獲取旋轉點的最小值和最大值:
min_box = (min(box_rotate, key=lambda p: p[0])[0], min(box_rotate, key=lambda p: p[1])[1])
max_box = (max(box_rotate, key=lambda p: p[0])[0], max(box_rotate, key=lambda p: p[1])[1])
通過將旋轉框的最小值添加到位置來計算圖像左上角點的“補償”原點。 對於 y 坐標max_box[1]
是最小值,因為沿 y 軸“翻轉”:
origin = (pos[0] + min_box[0], pos[1] - max_box[1])
rotated_image = pygame.transform.rotate(image, angle)
screen.blit(rotated_image, origin)
甚至可以在原始圖像上定義一個樞軸。 計算從圖像中心到樞軸的偏移向量並旋轉向量。 向量可以用pygame.math.Vector2
表示,也可以用pygame.math.Vector2.rotate
旋轉。 請注意, pygame.math.Vector2.rotate
的旋轉方向與pygame.transform.rotate
的相反。 因此必須反轉角度:
計算從圖像中心到樞軸的向量:
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
旋轉矢量
rotated_offset = offset_center_to_pivot.rotate(-angle)
計算旋轉圖像的中心:
rotated_image_center = (pos[0] - rotated_offset.x, pos[1] - rotated_offset.y)
旋轉和blit圖像:
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,函數blitRotate(surf, image, pos, originPos, angle)
執行上述所有步驟並將旋轉的圖像“blit”到表面。
surf
是目標表面
image
是必須旋轉和blit
的 Surface
pos
是目標 Surface surf
上樞軸的位置(相對於surf
的左上角)
originPos
是image
Surface 上樞軸的位置(相對於image
的左上角)
angle
是以度為單位的旋轉角度
這意味着, blitRotate
的第二個參數( pos
)是窗口中樞軸點的位置,第三個參數( originPos
)是旋轉Surface上的樞軸點位置:
最小的例子: repl.it/@Rabbid76/PyGame-RotateAroundPivot
import pygame
pygame.init()
screen = pygame.display.set_mode((300, 300))
clock = pygame.time.Clock()
def blitRotate(surf, image, pos, originPos, angle):
# offset from pivot to center
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
# roatated offset from pivot to center
rotated_offset = offset_center_to_pivot.rotate(-angle)
# roatetd image center
rotated_image_center = (pos[0] - rotated_offset.x, pos[1] - rotated_offset.y)
# get a rotated image
rotated_image = pygame.transform.rotate(image, angle)
rotated_image_rect = rotated_image.get_rect(center = rotated_image_center)
# rotate and blit the image
surf.blit(rotated_image, rotated_image_rect)
# draw rectangle around the image
pygame.draw.rect(surf, (255, 0, 0), (*rotated_image_rect.topleft, *rotated_image.get_size()),2)
def blitRotate2(surf, image, topleft, angle):
rotated_image = pygame.transform.rotate(image, angle)
new_rect = rotated_image.get_rect(center = image.get_rect(topleft = topleft).center)
surf.blit(rotated_image, new_rect.topleft)
pygame.draw.rect(surf, (255, 0, 0), new_rect, 2)
try:
image = pygame.image.load('AirPlaneFront.png')
except:
text = pygame.font.SysFont('Times New Roman', 50).render('image', False, (255, 255, 0))
image = pygame.Surface((text.get_width()+1, text.get_height()+1))
pygame.draw.rect(image, (0, 0, 255), (1, 1, *text.get_size()))
image.blit(text, (1, 1))
w, h = image.get_size()
angle = 0
done = False
while not done:
clock.tick(60)
for event in pygame.event.get():
if event.type == pygame.QUIT:
done = True
pos = (screen.get_width()/2, screen.get_height()/2)
screen.fill(0)
blitRotate(screen, image, pos, (w/2, h/2), angle)
#blitRotate2(screen, image, pos, angle)
angle += 1
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()
pygame.quit()
exit()
另請參閱旋轉曲面和問題的答案:
您正在刪除旋轉創建的矩形。 您需要保留矩形,因為它在旋轉時會改變大小。
如果要保留對象位置,請執行以下操作:
def rot_center(image, angle):
"""rotate a Surface, maintaining position."""
loc = image.get_rect().center #rot_image is not defined
rot_sprite = pygame.transform.rotate(image, angle)
rot_sprite.get_rect().center = loc
return rot_sprite
# or return tuple: (Surface, Rect)
# return rot_sprite, rot_sprite.get_rect()
置頂答案有一些問題: 函數中需要有前一個rect的位置,這樣我們才能將其分配給新的rect,例如:
rect = new_image.get_rect(center=rect.center)
在另一個答案中,位置是通過從原始圖像創建一個新的矩形來獲得的,但這意味着它將定位在默認的 (0, 0) 坐標處。
下面的示例應該可以正常工作。 新矩形需要舊矩形的center
位置,所以我們也將它傳遞給函數。 然后旋轉圖像,調用get_rect
得到一個大小正確的新矩形,並將舊矩形的center
屬性作為center
參數傳遞。 最后,將旋轉后的圖像和新矩形作為元組返回,並在主循環中解包。
import pygame as pg
def rotate(image, rect, angle):
"""Rotate the image while keeping its center."""
# Rotate the original image without modifying it.
new_image = pg.transform.rotate(image, angle)
# Get a new rect with the center of the old rect.
rect = new_image.get_rect(center=rect.center)
return new_image, rect
def main():
clock = pg.time.Clock()
screen = pg.display.set_mode((640, 480))
gray = pg.Color('gray15')
blue = pg.Color('dodgerblue2')
image = pg.Surface((320, 200), pg.SRCALPHA)
pg.draw.polygon(image, blue, ((0, 0), (320, 100), (0, 200)))
# Keep a reference to the original to preserve the image quality.
orig_image = image
rect = image.get_rect(center=(320, 240))
angle = 0
done = False
while not done:
for event in pg.event.get():
if event.type == pg.QUIT:
done = True
angle += 2
image, rect = rotate(orig_image, rect, angle)
screen.fill(gray)
screen.blit(image, rect)
pg.display.flip()
clock.tick(30)
if __name__ == '__main__':
pg.init()
main()
pg.quit()
這是另一個旋轉 pygame 精靈的示例。
import pygame as pg
class Entity(pg.sprite.Sprite):
def __init__(self, pos):
super().__init__()
self.image = pg.Surface((122, 70), pg.SRCALPHA)
pg.draw.polygon(self.image, pg.Color('dodgerblue1'),
((1, 0), (120, 35), (1, 70)))
# A reference to the original image to preserve the quality.
self.orig_image = self.image
self.rect = self.image.get_rect(center=pos)
self.angle = 0
def update(self):
self.angle += 2
self.rotate()
def rotate(self):
"""Rotate the image of the sprite around its center."""
# `rotozoom` usually looks nicer than `rotate`. Pygame's rotation
# functions return new images and don't modify the originals.
self.image = pg.transform.rotozoom(self.orig_image, self.angle, 1)
# Create a new rect with the center of the old rect.
self.rect = self.image.get_rect(center=self.rect.center)
def main():
screen = pg.display.set_mode((640, 480))
clock = pg.time.Clock()
all_sprites = pg.sprite.Group(Entity((320, 240)))
while True:
for event in pg.event.get():
if event.type == pg.QUIT:
return
all_sprites.update()
screen.fill((30, 30, 30))
all_sprites.draw(screen)
pg.display.flip()
clock.tick(30)
if __name__ == '__main__':
pg.init()
main()
pg.quit()
發現問題:示例效果很好,但寬度和高度需要相等的尺寸。 固定的圖片,它的工作原理。
在pygame
中繪制圖像所需的一切
game_display = pygame.display.set_mode((800, 600))
x = 0
y = 0
angle = 0
img = pygame.image.load("resources/image.png")
img = pygame.transform.scale(img, (50, 50)) # image size
def draw_img(self, image, x, y, angle):
rotated_image = pygame.transform.rotate(image, angle)
game_display.blit(rotated_image, rotated_image.get_rect(center=image.get_rect(topleft=(x, y)).center).topleft)
# run this method with your loop
def tick():
draw_img(img, x, y, angle)
我必須如下修改 skrx 解決方案,這種方式對我有用。
angle=0
roll = true
while roll:
# clean surface with your background color
gameDisplay.fill(color)
self.image = yourImage
rotate_image = pygame.transform.rotate(self.image, angle)
rect = rotate_image.get_rect()
pos = (((your_surface_width - rect.width)/2),((your_surface_height - rect.height)/2))
gameDisplay.blit(rotate_image,pos)
pygame.display.flip()
angle+=2
if angle == 360:
roll=False
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