蒙版
蒙版是二值化的图像，每个像素的值只能是0或1。
mask(蒙版)的用途：
- 碰撞检测
- 部分着色
案例
和字母的碰撞检测
当玩家碰到字母 α \alpha α时，改变玩家颜色为绿色，否则为红色。
注意：我们希望碰到字母 α \alpha α时才变色，而不是碰到字母 α \alpha α所在的矩形就变色。
# collisionif pygame.sprite.spritecollide(player.sprite,obstacle,False):if pygame.sprite.spritecollide(player.sprite,obstacle,False,pygame.sprite.collide_mask):player.sprite.image.fill('green')else:player.sprite.image.fill('red')
这里我们先用普通的精灵碰撞检测（矩形碰撞），如果发生了矩形碰撞，在使用蒙版碰撞将pygame.sprite.collide_mask作为参数传入pygame.sprite.spritecollide。
因为矩形检测比蒙版检测速度快很多，这样做可以减少蒙版检测的次数，提高效率。
https://www.pygame.org/docs/ref/sprite.html#pygame.sprite.spritecollide
完整代码：
import pygame, sys class Player(pygame.sprite.Sprite):def __init__(self):super().__init__()self.image = pygame.Surface((40,40)) self.image.fill('red')self.rect = self.image.get_rect(center = (300,300))self.mask = pygame.mask.from_surface(self.image)def update(self):if pygame.mouse.get_pos():self.rect.center = pygame.mouse.get_pos()class Obstacle(pygame.sprite.Sprite):def __init__(self):super().__init__()self.image = pygame.image.load('alpha.png').convert_alpha()self.rect = self.image.get_rect(center = (400,400))self.mask = pygame.mask.from_surface(self.image)# pygame setup
pygame.init()
screen = pygame.display.set_mode((800,800))
clock = pygame.time.Clock()# group setup
player = pygame.sprite.GroupSingle(Player())
obstacle = pygame.sprite.GroupSingle(Obstacle())while True:for event in pygame.event.get():if event.type == pygame.QUIT:pygame.quit()sys.exit()screen.fill('white')obstacle.draw(screen) # updating and drawing player.update()player.draw(screen)# collisionif pygame.sprite.spritecollide(player.sprite,obstacle,False):if pygame.sprite.spritecollide(player.sprite,obstacle,False,pygame.sprite.collide_mask):player.sprite.image.fill('green')else:player.sprite.image.fill('red')pygame.display.update()clock.tick(60)
图片轮廓
将字母 α \alpha α的轮廓变成橘色。
我们需要：
- 从surface 创建mask.
- 将mask变成surface.
- 使用2中的surface创建轮廓(silhouette)
- 显示轮廓。
import pygame,syspygame.init()
screen = pygame.display.set_mode((800,800))
clock = pygame.time.Clock()# creating the obstacle
obstacle_surf = pygame.image.load('alpha.png').convert_alpha()
obstacle_pos = (100,100)
# 1. surface -> mask
obstacle_mask = pygame.mask.from_surface(obstacle_surf)# 2. mask -> surface
new_obstacle_surf = obstacle_mask.to_surface()
# 与colorkey相同的像素变透明
new_obstacle_surf.set_colorkey((0,0,0))# 4. filling in the surface with a color
surf_w,surf_h = new_obstacle_surf.get_size()
for x in range(surf_w):for y in range(surf_h):if new_obstacle_surf.get_at((x,y))[0] != 0:new_obstacle_surf.set_at((x,y),'orange')while True:for event in pygame.event.get():if event.type == pygame.QUIT:pygame.quit()sys.exit()screen.fill('grey')# complex way for a outlineoffset = 4screen.blit(new_obstacle_surf,(obstacle_pos[0] + offset,obstacle_pos[1])) # rightscreen.blit(new_obstacle_surf,(obstacle_pos[0] - offset,obstacle_pos[1])) # leftscreen.blit(new_obstacle_surf,(obstacle_pos[0], obstacle_pos[1] - offset)) # topscreen.blit(new_obstacle_surf,(obstacle_pos[0], obstacle_pos[1] + offset)) # bottomscreen.blit(new_obstacle_surf,(obstacle_pos[0] + offset, obstacle_pos[1] - offset)) # toprightscreen.blit(new_obstacle_surf,(obstacle_pos[0] + offset, obstacle_pos[1] + offset)) # bottomrightscreen.blit(new_obstacle_surf,(obstacle_pos[0] - offset, obstacle_pos[1] + offset)) # bottomleftscreen.blit(new_obstacle_surf,(obstacle_pos[0] - offset, obstacle_pos[1] - offset)) # topleftscreen.blit(obstacle_surf,obstacle_pos)# simple way to create an outline from a mask# for point in obstacle_mask.outline():# x = point[0] + obstacle_pos[0]# y = point[1] + obstacle_pos[1]# pygame.draw.circle(screen,'red',(x,y),1)pygame.display.update()clock.tick(60)
重叠部分着色
- 使用
overlap_mask获得重叠部分的mask - 重新设置重叠部分mask的颜色。
import pygame,syspygame.init()
screen = pygame.display.set_mode((800,800))
clock = pygame.time.Clock()# ship setup
ship_surf = pygame.image.load('ship.png').convert_alpha()
ship_overlay_surf = pygame.image.load('ship.png').convert_alpha()
ship_rect = ship_surf.get_rect(center = (300,300))
ship_mask = pygame.mask.from_surface(ship_surf)# obstacle setup
obstacle_surf = pygame.image.load('alpha.png').convert_alpha()
obstacle_pos = (100,100)
obstacle_mask = pygame.mask.from_surface(obstacle_surf)while True:for event in pygame.event.get():if event.type == pygame.QUIT:pygame.quit()sys.exit()screen.fill('white')# obstacle screen.blit(obstacle_surf,obstacle_pos)# moving partif pygame.mouse.get_pos():ship_rect.center = pygame.mouse.get_pos()screen.blit(ship_surf,ship_rect)# mask coloring offset_x = obstacle_pos[0] - ship_rect.leftoffset_y = obstacle_pos[1] - ship_rect.topif ship_mask.overlap(obstacle_mask,(offset_x,offset_y)):new_mask = ship_mask.overlap_mask(obstacle_mask,(offset_x,offset_y))new_surf = new_mask.to_surface()new_surf.set_colorkey((0,0,0))surf_w, surf_h = new_surf.get_size()for x in range(surf_w):for y in range(surf_h):if new_surf.get_at((x,y))[0] != 0:new_surf.set_at((x,y),'orange')screen.blit(new_surf,ship_rect)pygame.display.update()clock.tick(60)
