如何在Pygame中更改图像的颜色而不更改其透明度？

Question

It sounds like a simple thing to do , but I'm struggling. I have a png image of a rectangle with a transparent centre called "zero". I want to change the colour of the visible part of the image. To try and change it, I have tried using "zero.fill" but no option I try changes only the non-transparent part, or it merges the new colour with the old and stays like that. I'm not keen on installing numpy as I wish to take the finished program to a friend who doesn't have it. Any simple suggestions welcome.

Answer 1

I've got an example that works with per pixel alpha surfaces that can also be translucent. The fill function just loops over the surface's pixels and sets them to the new color, but keeps their alpha value. It's probably not recommendable to do this every frame with many surfaces. (Press f, g, h to change the color.)

import sys
import pygame as pg


def fill(surface, color):
    """Fill all pixels of the surface with color, preserve transparency."""
    w, h = surface.get_size()
    r, g, b, _ = color
    for x in range(w):
        for y in range(h):
            a = surface.get_at((x, y))[3]
            surface.set_at((x, y), pg.Color(r, g, b, a))


def main():
    screen = pg.display.set_mode((640, 480))
    clock = pg.time.Clock()

    # Uncomment this for a non-translucent surface.
    # surface = pg.Surface((100, 150), pg.SRCALPHA)
    # pg.draw.circle(surface, pg.Color(40, 240, 120), (50, 50), 50)
    surface = pg.image.load('bullet2.png').convert_alpha()
    surface = pg.transform.rotozoom(surface, 0, 2)

    done = False

    while not done:
        for event in pg.event.get():
            if event.type == pg.QUIT:
                done = True
            if event.type == pg.KEYDOWN:
                if event.key == pg.K_f:
                    fill(surface, pg.Color(240, 200, 40))
                if event.key == pg.K_g:
                    fill(surface, pg.Color(250, 10, 40))
                if event.key == pg.K_h:
                    fill(surface, pg.Color(40, 240, 120))

        screen.fill(pg.Color('lightskyblue4'))
        pg.draw.rect(screen, pg.Color(40, 50, 50), (210, 210, 50, 90))
        screen.blit(surface, (200, 200))

        pg.display.flip()
        clock.tick(30)


if __name__ == '__main__':
    pg.init()
    main()
    pg.quit()
    sys.exit()

Answer 2

In this version, the visible and transparent parts are the other way round to the original question as per Ankur's suggestion. Here is the essential working code:

import pygame, sys
from pygame.locals import *
pygame.init()

def load_image(name):
    image = pygame.image.load(name).convert()
    return image

def resize(obj, w, h):
    global scale
    return pygame.transform.scale(obj, (int(w * scale), int(h * scale)))


pink = (255, 0, 160)
red = (255, 0, 0)
peach = (255, 118, 95)
blue = (0, 0, 255)
blue_1 = (38, 0, 160)
dark_yellow = (255, 174, 0)
green = (38, 137, 0)
orange = (255, 81, 0)
colour = [pink, red, peach, blue, blue_1, dark_yellow, green, orange, green]
clock = pygame.time.Clock()
scale = 4
screen = pygame.display.set_mode((292 * scale, 240 * scale),0, 32)
banner = load_image("banner.png") #292x35
zero = load_image("zero.png") #5x7
c = 0
while True:
    for event in pygame.event.get():
        if event.type == QUIT:
            pygame.quit()
            sys.exit()
    rgb = colour[c]
    c = c + 1
    if c > 7:
        c = 0
    pygame.draw.line(banner, rgb, (53, 21), (53, 27), 5) #line the same size as zero image
    banner.blit(zero, (51, 21)) #blit image with transparency over line
    large_banner = resize(banner, 292, 35)
    screen.blit(large_banner, (0, 0))
    clock.tick(120)
    pygame.display.flip()

pygame.quit()
sys.exit()

Answer 3

This code for drop all color brightness

    def drop(surface):
        w, h = surface.get_size()
        for x in range(w):
            for y in range(h):
                r = surface.get_at((x, y))[0]
                if r>150:
                   r-=50
                g = surface.get_at((x, y))[1]
                if g>150:
                   g-=50
                b = surface.get_at((x, y))[2]
                if b>150:
                   b-=50
                a = surface.get_at((x, y))[3]
                surface.set_at((x, y), pygame.Color(r, g, b, a)) 

    img = pygame.image.load("image.png").convert_alpha()
    drop(img)