Pygame convert list of shapes to mask

The goal is to reveal an image in the background at the same time that a shape or a couple of shapes go through the screen. My approach is to create a list of shapes (rects or circles), then converting al that to a mask and then fill the screen all black but the masks every loop.

Is there a way to make a mask with a list of shapes? I checked pygame.mask (https://www.pygame.org/docs/ref/mask.html?highlight=mask#module-pygame.mask) but cant see a way to convert list of shapes to mask. Any advice?

What you can do is to create a Mask for each shape and one Mask to fill (cover) the entire screen.

Then, for each shape mask created this way, update the screen mask with Mask.draw, something like this:

    for rect, mask in surfaces:
screen_mask.draw(mask, rect.topleft)

where surfaces is a list of Rect/Mask tuples.

Then you can use the screen mask to cover the screen, e.g. with Mask.to_surface like this:

new_background = screen_mask.to_surface(background.copy(), setsurface=background)
screen.blit(new_background, (0, 0))

where background is your original background image, screen_mask the mask that should cover the screen and new_background is the surface you draw instead of background.

Here's an example I hacked together; you'll get the idea:

import pygame, math
def main():
d = 0
pygame.init()
screen = pygame.display.set_mode((640, 960))
img = pygame.image.load('pexels-stijn-dijkstra-16745023.jpg').convert()
triangle = pygame.Surface((32, 32))
triangle.set_colorkey((0,0,0))
pygame.draw.lines(triangle, 'red', True, ((0, 0), (32, 0), (16, 32)), 8)
triangle_rect = triangle.get_frect(center=(400, 100))
triangle_mask = pygame.mask.from_surface(triangle)
circle = pygame.Surface((32, 32))
circle.set_colorkey((0,0,0))
pygame.draw.circle(circle, 'yellow', (16, 16), 16)
pygame.draw.circle(circle, 'black', (16, 16), 12)
circle_rect = circle.get_frect(center=(200, 400))
circle_mask = pygame.mask.from_surface(circle)
surfaces = (
(triangle, triangle_rect, triangle_rect, triangle_mask), 
(circle, circle_rect, circle_rect, circle_mask)
)
cloack = pygame.mask.Mask((640, 960))
clock = pygame.time.Clock()
while True:
for e in pygame.event.get():
if e.type == pygame.QUIT or e.type == pygame.KEYDOWN and e.key == pygame.K_ESCAPE:
return
for surface, rect, base, mask in surfaces:
cloack.draw(mask, rect.topleft)
rect.x = base.x + math.sin(0.01 * pygame.time.get_ticks()) * 10
rect.y += 0.5
back = cloack.to_surface(img.copy(), setsurface=img)
screen.blit(back, (0, 0))
for surface, rect, base, mask in surfaces:
screen.blit(surface, rect)
pygame.display.flip()
d = clock.tick(60)
main()