问题
So I am trying to fade my screen out and back in after completing a level using PyGame. My problem is that only the fadeout() works and not the fadein(). When calling the fadein() the screen turns black for a few seconds then suddenly shows the next level. I can't find the problem, any ideas?
def fadeout():
fadeout = pg.Surface((screen_width, screen_height))
fadeout = fadeout.convert()
fadeout.fill(black)
for i in range(255):
fadeout.set_alpha(i)
screen.blit(fadeout, (0, 0))
pg.display.update()
def fadein():
fadein = pg.Surface((screen_width, screen_height))
fadein = fadein.convert()
fadein.fill(black)
for i in range(255):
fadein.set_alpha(255-i)
screen.blit(fadein, (0, 0))
pg.display.update()
回答1:
Your problem is that you fade in to a black screen, so you don't see any effect. A black screen with a black half-translucent Surface
drawn on top is still a black Surface
.
You should render the first frame of your level, and blit that Surface
to the screen before blitting the fadein
surface onto the screen.
Here's a simple example that I hacked together. Press a key to switch from one scene to the next.
import pygame
import random
from itertools import cycle
class Cloud(pygame.sprite.Sprite):
def __init__(self, x, y):
super().__init__()
self.image = pygame.Surface((50, 20))
self.image.set_colorkey((11, 12, 13))
self.image.fill((11, 12, 13))
pygame.draw.ellipse(self.image, pygame.Color('white'), self.image.get_rect())
self.rect = self.image.get_rect(topleft=(x,y))
def update(self, dt, events):
self.rect.move_ip(dt/10, 0)
if self.rect.left >= pygame.display.get_surface().get_rect().width:
self.rect.right = 0
class DayScene:
def __init__(self):
self.clouds = pygame.sprite.Group(Cloud(0, 30), Cloud(100, 40), Cloud(400, 50))
def draw(self, screen):
screen.fill(pygame.Color('lightblue'))
self.clouds.draw(screen)
def update(self, dt, events):
self.clouds.update(dt, events)
class NightScene:
def __init__(self):
sr = pygame.display.get_surface().get_rect()
self.sky = pygame.Surface(sr.size)
self.sky.fill((50,0,50))
for x in random.sample(range(sr.width), 50):
pygame.draw.circle(self.sky, (200, 200, 0), (x, random.randint(0, sr.height)), 1)
self.clouds = pygame.sprite.Group(Cloud(70, 70), Cloud(60, 40), Cloud(0, 50), Cloud(140, 10), Cloud(100, 20))
def draw(self, screen):
screen.blit(self.sky, (0, 0))
self.clouds.draw(screen)
def update(self, dt, events):
self.clouds.update(dt, events)
class Fader:
def __init__(self, scenes):
self.scenes = cycle(scenes)
self.scene = next(self.scenes)
self.fading = None
self.alpha = 0
sr = pygame.display.get_surface().get_rect()
self.veil = pygame.Surface(sr.size)
self.veil.fill((0, 0, 0))
def next(self):
if not self.fading:
self.fading = 'OUT'
self.alpha = 0
def draw(self, screen):
self.scene.draw(screen)
if self.fading:
self.veil.set_alpha(self.alpha)
screen.blit(self.veil, (0, 0))
def update(self, dt, events):
self.scene.update(dt, events)
if self.fading == 'OUT':
self.alpha += 8
if self.alpha >= 255:
self.fading = 'IN'
self.scene = next(self.scenes)
else:
self.alpha -= 8
if self.alpha <= 0:
self.fading = None
def main():
screen_width, screen_height = 300, 300
screen = pygame.display.set_mode((screen_width, screen_height))
clock = pygame.time.Clock()
dt = 0
fader = Fader([DayScene(), NightScene()])
while True:
events = pygame.event.get()
for e in events:
if e.type == pygame.QUIT:
return
if e.type == pygame.KEYDOWN:
fader.next()
fader.draw(screen)
fader.update(dt, events)
pygame.display.flip()
dt = clock.tick(30)
main()
By abstracting each scene into it's own class and delegating the scene change to the Fader
class, we're able to let the scenes continue (or add a simple if
statement to prevent that) and to handle events while fading.
来源:https://stackoverflow.com/questions/58540537/how-to-fade-the-screen-out-and-back-in-using-pygame