Pygame基础11-mask 蒙版

Pygame基础11-mask 蒙版

Mask是二值化的图像，每个像素的值只能是0或1。Mask的主要用途包括碰撞检测和部分着色。

和字母的碰撞检测

当玩家碰到字母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时才变色，而不是碰到字母α所在的矩形就变色。

# collision
if 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。

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)
    
    # collision
    if 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的轮廓变成橘色。我们需要：

1. 从surface 创建mask.
2. 将mask变成surface.
3. 使用2中的surface创建轮廓(silhouette)
4. 显示轮廓。

import pygame,sys
pygame.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 outline
    offset = 4
    screen.blit(new_obstacle_surf,(obstacle_pos[0] + offset,obstacle_pos[1])) # right
    screen.blit(new_obstacle_surf,(obstacle_pos[0] - offset,obstacle_pos[1])) # left
    screen.blit(new_obstacle_surf,(obstacle_pos[0], obstacle_pos[1] - offset)) # top
    screen.blit(new_obstacle_surf,(obstacle_pos[0], obstacle_pos[1] + offset)) # bottom
    screen.blit(new_obstacle_surf,(obstacle_pos[0] + offset, obstacle_pos[1] - offset)) # topright
    screen.blit(new_obstacle_surf,(obstacle_pos[0] + offset, obstacle_pos[1] + offset)) # bottomright
    screen.blit(new_obstacle_surf,(obstacle_pos[0] - offset, obstacle_pos[1] + offset)) # bottomleft
    screen.blit(new_obstacle_surf,(obstacle_pos[0] - offset, obstacle_pos[1] - offset)) # topleft
    screen.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

1. 使用overlap_mask获得重叠部分的mask
2. 重新设置重叠部分mask的颜色。

import pygame,sys
pygame.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 part
    if 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.left
    offset_y = obstacle_pos[1] - ship_rect.top
    if 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)