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#!/usr/bin/env python
"""
pygame.examples.mask
A pygame.mask collision detection production.
Brought
to
you
by
the
pixels
0000000000000
and
111111
This is 32 bits:
11111111111111111111111111111111
There are 32 or 64 bits in a computer 'word'.
Rather than using one word for a pixel,
the mask module represents 32 or 64 pixels in one word.
As you can imagine, this makes things fast, and saves memory.
Compute intensive things like collision detection,
and computer vision benefit greatly from this.
This module can also be run as a stand-alone program, excepting
one or more image file names as command line arguments.
"""
import os
import random
import sys
import pygame as pg
class Sprite:
"""
Moving Sprite demonstrating pixel-perfect collisions between pg.mask.Mask objects
"""
def __init__(self, pos, vel, surface, mask=None):
"""
Positional arguments:
pos: Position of the sprite (sequence of 2 integers)
vel: Movement velocity of the sprite (sequence of 2 integers)
surface: Image (as a pg.Surface) of the sprite
mask: pg.mask.Mask object (optional)
"""
self.surface = surface
self.width, self.height = self.surface.get_size()
if mask is not None:
self.mask = mask
else:
self.mask = pg.mask.from_surface(self.surface)
self.pos = pg.Vector2(pos)
self.vel = pg.Vector2(vel)
def collide(self, sprite):
"""
Test if the sprites are colliding and
resolve the collision in this case.
Positional arguments:
sprite: other sprite to test for collisions
"""
offset = [int(x) for x in sprite.pos - self.pos]
overlap = self.mask.overlap_area(sprite.mask, offset)
if overlap == 0:
return
# Calculate collision normal
# Number of collisions
n_collisions = pg.Vector2(
# x axis
self.mask.overlap_area(sprite.mask, (offset[0] + 1, offset[1]))
- self.mask.overlap_area(sprite.mask, (offset[0] - 1, offset[1])),
# y axis
self.mask.overlap_area(sprite.mask, (offset[0], offset[1] + 1))
- self.mask.overlap_area(sprite.mask, (offset[0], offset[1] - 1)),
)
if n_collisions.x == 0 and n_collisions.y == 0:
# One sprite is inside another
return
delta_vel = sprite.vel - self.vel
j = delta_vel * n_collisions / (2 * n_collisions * n_collisions)
if j > 0:
# Can scale up to 2*j here to get bouncy collisions
j *= 1.9
self.vel += [n_collisions.x * j, n_collisions.y * j]
sprite.vel += [-j * n_collisions.x, -j * n_collisions.y]
# # Separate the sprites
# c1 = -overlap / (n_collisions * n_collisions)
# c2 = -c1 / 2
# self.pos += [c2 * n_collisions.x, c2 * n_collisions.y]
# sprite.pos += [(c1 + c2) * n_collisions.x, (c1 + c2) * n_collisions.y]
def update(self):
"""
Move the sprite
"""
self.pos += self.vel
def main(*args):
"""
Display multiple images bounce off each other using collision detection
Positional arguments:
one or more image file names.
This pg.masks demo will display multiple moving sprites bouncing
off each other. More than one sprite image can be provided.
"""
if len(args) == 0:
raise ValueError("Require at least one image file name: non given")
pg.init()
screen_size = (640, 480)
screen = pg.display.set_mode(screen_size)
clock = pg.time.Clock()
images = []
masks = []
for image_path in args:
images.append(pg.image.load(image_path).convert_alpha())
masks.append(pg.mask.from_surface(images[-1]))
sprites = []
for i in range(20):
j = i % len(images)
sprite = Sprite(
pos=(
random.uniform(0, screen_size[0]),
random.uniform(0, screen_size[1]),
),
vel=(
random.uniform(-5, 5),
random.uniform(-5, 5),
),
surface=images[j],
mask=masks[j],
)
sprites.append(sprite)
while True:
for event in pg.event.get():
if event.type in (pg.QUIT, pg.KEYDOWN):
return
screen.fill((240, 220, 100))
for sprite_index, sprite in enumerate(sprites):
for other_sprite in sprites[sprite_index + 1 :]:
sprite.collide(other_sprite)
sprite.update()
# If the sprite is outside of the screen on the left
if sprite.pos.x < -sprite.width:
sprite.pos.x = screen_size[0]
# right
elif sprite.pos.x > screen_size[0]:
sprite.pos.x = -sprite.width
# top
if sprite.pos.y < -sprite.height:
sprite.pos.y = screen_size[1]
# down
elif sprite.pos.y > screen_size[1]:
sprite.pos.y = -sprite.height
screen.blit(sprite.surface, sprite.pos)
clock.tick(30)
pg.display.flip()
if __name__ == "__main__":
if len(sys.argv) < 2:
print("Usage: mask.py <IMAGE> [<IMAGE> ...]")
print("Let many copies of IMAGE(s) bounce against each other")
print("Press any key to quit")
main_dir = os.path.split(os.path.abspath(__file__))[0]
main(os.path.join(main_dir, "data", "alien1.png"))
else:
main(*sys.argv[1:])
pg.quit()
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