更改表面颜色而不覆盖透明度

如何解决更改表面颜色而不覆盖透明度

我想在运行时动态更改rect的颜色。当前set_colour用单一颜色值填充表面的所有像素。这行得通，但是在调用set_outline之类的方法时会出现问题，该方法会修改表面的透明度。

class Rectangle(pg.sprite.Sprite):
    def __init__(self):
        pg.sprite.Sprite.__init__(self)
        self.original_image = pg.Surface((10,10))
        self.image = self.original_image
        self.rect = self.image.get_rect()

    def set_colour(self,colour_value):
        self.colour = colour_value
        self.image.fill(self.colour)
        self.original_image.fill(self.colour)

    def set_outline(self,thickness):
        self.thickness = thickness
        size = self.image.get_size()

        calc = thickness/100
        p_width,p_height = size[0],size[1]
        width,height = size[0]*calc,size[1]*calc

        self.image = self.image.convert_alpha()

        center_x,center_y = (p_width//2)-(width//2),(p_height//2)-(height//2)
        pg.draw.rect(self.image,(0,0),(center_x,center_y,width,height))

现在，如果我尝试在运行时更改该矩形的颜色，它将覆盖在set_outline中创建的所有透明像素。

有没有一种方法可以将颜色遮罩或混合到矩形上，从而不会替换任何透明性？

解决方法

您可以通过2个步骤来实现。 self.original_image包含具有所需颜色的填充矩形：

self.original_image.fill(self.colour)

生成一个完全白色的矩形和透明区域。将矩形与（self.image）和混合模式BLEND_MAX（请参见 pygame.Surface.blit）混合：

whiteTransparent = pg.Surface(self.image.get_size(),pg.SRCALPHA)
whiteTransparent.fill((255,255,0))
self.image.blit(whiteTransparent,(0,0),special_flags=pg.BLEND_MAX)

现在，矩形是完全白色的，但是透明区域得以保留。使用混合模式BLEND_MULT并将self.original_image与self.image混合以获得所需的结果：

self.image.blit(self.original_image,special_flags=pg.BLEND_MULT)

---

最小示例： repl.it/@Rabbid76/PyGame-ChangeColorOfSpriteArea

import pygame as pg

class Rectangle(pg.sprite.Sprite):
    def __init__(self):
        pg.sprite.Sprite.__init__(self)
        self.original_image = pg.Surface((150,150))
        self.image = self.original_image
        self.rect = self.image.get_rect(center = (150,150))

    def set_colour(self,colour_value):
        self.colour = colour_value
        self.original_image.fill(self.colour)

        whiteTransparent = pg.Surface(self.image.get_size(),pg.SRCALPHA)
        whiteTransparent.fill((255,0))
        self.image.blit(whiteTransparent,special_flags=pg.BLEND_MAX)

        self.image.blit(self.original_image,special_flags=pg.BLEND_MULT)

    def set_outline(self,thickness):
        self.thickness = thickness
        size = self.image.get_size()

        calc = thickness/100
        p_width,p_height = size[0],size[1]
        width,height = size[0]*calc,size[1]*calc

        self.image = self.image.convert_alpha()

        center_x,center_y = (p_width//2)-(width//2),(p_height//2)-(height//2)
        pg.draw.rect(self.image,(center_x,center_y,width,height))

pg.init()
window = pg.display.set_mode((300,300))
clock = pg.time.Clock()

sprite = Rectangle()
sprite.set_colour((255,255))
sprite.set_outline(50)

group = pg.sprite.Group(sprite)

colorVal = 0
colorAdd = 5
run = True
while run:
    clock.tick(60)
    for event in pg.event.get():
        if event.type == pg.QUIT:
            run = False

    sprite.set_colour((min(colorVal,255),max(0,min(511-colorVal,255)),255))
    colorVal += colorAdd
    if colorVal <= 0 or colorVal >= 511:
        colorAdd *= -1

    window.fill(0)
    group.draw(window)
    pg.display.flip()