如何在 pygame 中检测鼠标悬停在图像（圆形）上

Question

如果图像检测到鼠标悬停，我需要缩放图像，但我不知道方法。我认为使用 pygame.mouse.get_pos() 和图像的 rect 很难检测到它，因为图像是圆形而不是矩形。它可能会检测到鼠标悬停，但鼠标位于图像的一角，而不是触摸它。

Answer 1

可以使用Pythagorean theorem to calculate the distance between the mouse and the circle center or just math.hypot。如果距离小于半径，则鼠标与圆碰撞。

另外，为图片创建一个rect作为blit位置，方便获取中心点。

import math
import pygame as pg


pg.init()
screen = pg.display.set_mode((640, 480))
clock = pg.time.Clock()
BG_COLOR = pg.Color('gray12')

radius = 60  # Circle radius.
IMAGE = pg.Surface((120, 120), pg.SRCALPHA)
pg.draw.circle(IMAGE, (225, 0, 0), (radius, radius), radius)
# Use this rect to position the image.
rect = IMAGE.get_rect(center=(200, 200))

done = False
while not done:
    for event in pg.event.get():
        if event.type == pg.QUIT:
            done = True
        elif event.type == pg.MOUSEMOTION:
            mouse_pos = event.pos  # Or `pg.mouse.get_pos()`.
            # Calculate the x and y distances between the mouse and the center.
            dist_x = mouse_pos[0] - rect.centerx
            dist_y = mouse_pos[1] - rect.centery
            # Calculate the length of the hypotenuse. If it's less than the
            # radius, the mouse collides with the circle.
            if math.hypot(dist_x, dist_y) < radius:
                print('collision')

    screen.fill(BG_COLOR)
    screen.blit(IMAGE, rect)
    pg.display.flip()
    clock.tick(60)

pg.quit()

如果您要处理精灵，也可以使用 masks for pixel-perfect collision detection or pygame.sprite.collide_circle。

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