绘制一个曲面并用pygam旋转

Question

我试图在Python中用命令模拟JS中可用的一些行为上下文.旋转（角度）。在

我有以下代码： 导入pygame 导入数学 将numpy作为np导入

pygame.init()

CLOCK = pygame.time.Clock()
RED = pygame.color.THECOLORS['red']
WHITE = pygame.color.THECOLORS['white']
screen = pygame.display.set_mode((0, 0), pygame.FULLSCREEN)
screen_width, screen_height = screen.get_size()
surface = pygame.Surface((50, 50), pygame.SRCALPHA)
surface.fill((0, 0, 0))
rotated_surface = surface
rect = surface.get_rect()
ax = int(screen_width / 2)
ay = int(screen_height / 2)
angle = 0
print("Size of the screen ({}, {})".format(screen_width, screen_height))
print("Center of the screen ({}, {})".format(ax, ay))
myfont = pygame.font.SysFont("monospace", 12)

pygame.display.set_caption("Test rotate")

main_loop = True
amplifier = 200


def calculate_angle(mouse_position):
    dx = mouse_position[0] - ax
    dy = mouse_position[1] - ay
    return np.arctan2(dy,dx)

while main_loop:
    for event in pygame.event.get():
        keys = pygame.key.get_pressed()
        if event.type == pygame.QUIT or keys[pygame.K_ESCAPE]:
            main_loop = False

    pos = pygame.mouse.get_pos()
    angle = (calculate_angle(pos) * 180)/math.pi
    screen.fill((255,255,255))
    rotated_surface = pygame.transform.rotate(surface, -angle)
    rect = rotated_surface.get_rect(center = (ax, ay))
    screen.blit(rotated_surface, (rect.x, rect.y))
    pygame.draw.line(rotated_surface, WHITE, (ax,ay), (ax+20, ay), 1)
    pygame.draw.line(rotated_surface, WHITE, (ax+10,ay-10), (ax+20, ay), 1)
    pygame.draw.line(rotated_surface, WHITE, (ax+10,ay+10), (ax+20, ay), 1)
    pygame.display.update()
    CLOCK.tick(30)


pygame.quit()

我画了一个箭头，想根据鼠标在屏幕上的位置旋转它。当然，每次做正弦、余弦计算时，我都可以重新画出线条，但这很痛苦。我认为曲面可以帮助我，事实上，它与完美旋转的矩形一起工作。但是把我的线条画到表面上是行不通的。在

所以，我想我误解了曲面的用途，或者我把代码写错了，还有更好的方法。请注意，如果我在绘制线说明，箭头确实在屏幕上绘制，但永远不会旋转。在

有什么想法（除了使用image/sprite；）？在

谢谢

Answer 1

问题是在曲面区域之外绘制箭头线。每个曲面的左上角坐标为（0，0），因此它们都有自己的（局部）坐标系。因为你用屏幕的中心坐标来画线，所以箭头不会在可见的表面区域绘制。在

我用局部坐标在while循环前面的原始曲面上画线，然后旋转它，在循环内部得到一个新的rect。在

import math
import pygame


pygame.init()

CLOCK = pygame.time.Clock()
GRAY = pygame.color.THECOLORS['gray50']
WHITE = pygame.color.THECOLORS['white']
screen = pygame.display.set_mode((800, 600))
screen_rect = screen.get_rect()  # A rect with the size of the screen.
surface = pygame.Surface((50, 50), pygame.SRCALPHA)
# surface.fill((0, 50, 150))  # Fill the surface to make it visible.
# Use the local coordinate system of the surface to draw the lines.
pygame.draw.line(surface, WHITE, (0, 0), (25, 0), 1)
pygame.draw.line(surface, WHITE, (0, 0), (25, 25), 1)
pygame.draw.line(surface, WHITE, (0, 0), (0, 25), 1)
# I rotate it so that the arrow is pointing to the right (0° is right).
surface = pygame.transform.rotate(surface, -135)
rect = surface.get_rect()
angle = 0
# If you're using Python 3.6+, you can use f-strings.
print(f"Size of the screen {screen.get_size()}")
print(f"Center of the screen {screen_rect.center}")

def calculate_angle(mouse_position):
    dx = mouse_position[0] - screen_rect.centerx
    dy = mouse_position[1] - screen_rect.centery
    return math.atan2(dy, dx)

main_loop = True
while main_loop:
    for event in pygame.event.get():
        # You shouldn't use `pygame.key.get_pressed` in the event loop.
        if (event.type == pygame.QUIT
            or event.type == pygame.KEYDOWN and event.key == pygame.K_ESCAPE):
            main_loop = False

    pos = pygame.mouse.get_pos()
    angle = math.degrees(calculate_angle(pos))
    screen.fill(GRAY)
    # Now just rotate the original surface and get a new rect.
    rotated_surface = pygame.transform.rotate(surface, -angle)
    rect = rotated_surface.get_rect(center=(screen_rect.center))
    screen.blit(rotated_surface, rect)
    pygame.display.update()
    CLOCK.tick(30)


pygame.quit()

我还试图改进一些东西（查看评论）。在