如何使用pygame Python使表面/图像每秒闪烁2次

Question

Experimenting with pygame lately and have come across alpha opacity. How is it possible to tune the range of alpha so that my my image/surface will blink two times a second?

Currently I'm drawing this at 30 frames per second.

def blit_image(self):
        for alpha in range(0,255,50):
            for i in self.image_array:
                a = i.set_alpha(alpha)
                i.draw_on(self.screen)
        pygame.display.flip()

Something isn't right here, it's only making the borders of my image opaque, I'm unable to see if the blink is even actually happening. Any thoughts of how to do this?

Answer 1

Briefly: (your code) You have 30 frames per second (30FPS) so every frame you decrease alpha +1/15 * 255 and after 15 frames you increase alpha -1/15 * 255 and after 15 frames you again decrease etc.

It is full example how to blink background color (it was answer for similar question on SO). It is not exacly what you do but maybe it helps you.

import pygame

#----------------------------------------------------------------------

class Background():

    def __init__(self, screen):
        self.screen = screen

        self.timer = 0
        self.color = 0
        self.up = True # up or down

    #-------------------

    def change(self):

        if self.timer == 15: # 15 frames for UP and 15 frames for DOWN
            self.timer = 0
            self.up = not self.up

        self.timer += 1

        if self.up:
            self.color += 10
        else:
            self.color -= 10

        print self.up, self.color

    #-------------------

    def draw(self):
        self.screen.fill( (self.color, self.color, self.color) )

#----------------------------------------------------------------------

class Game():

    def __init__(self):
        pygame.init()

        self.screen = pygame.display.set_mode((800,600))

        self.background = Background(self.screen)

    #-------------------

    def run(self):

        clock = pygame.time.Clock()

        RUNNING = True

        while RUNNING:

            # ----- events -----

            for event in pygame.event.get():
                if event.type == pygame.QUIT:
                    RUNNING = False
                if event.type == pygame.KEYDOWN:
                    if event.key == pygame.K_ESCAPE:
                        RUNNING = False

            # ----- changes -----

            self.background.change()

            # ----- draws ------

            self.background.draw()

            pygame.display.update()

            # ----- FPS -----

            clock.tick(30)

        #-------------------

        pygame.quit()

#----------------------------------------------------------------------

Game().run()