sprite_packer

sprite_packer.py

import json
from pathlib import Path

from PIL import Image


# Build sprite list
sprites_folder = Path("./sprites")
sprites = []
for file in sprites_folder.iterdir():
    if file.suffix == ".png":
        sprite = Image.open(file)
        sprites.append(sprite)

# Sort sprites from largest to smallest area
sprites.sort(key=lambda s: s.height * s.width, reverse=True)

# Create atlas
atlas_size = (512, 512)
while True:
    atlas = Image.new(mode="RGBA", size=atlas_size)
    sprite_data = {}
    packing_failed = False

    # Empty areas in the atlas
    area = (0, 0, atlas_size[0], atlas_size[1])  # (x, y, w, h)
    areas = [area]

    # Pack sprites using the Guillotine algorithm
    for sprite in sprites:
        # Find an empty area
        area = None
        for a in areas:
            x, y, w, h = a
            if sprite.width <= w and sprite.height <= h:
                # Add the sprite to the atlas
                atlas.paste(sprite, box=(x, y))
                sprite_name = Path(sprite.filename).name
                sprite_data[sprite_name] = {'x': x, 'y': y, 'w': sprite.width, 'h': sprite.height}
                area = a
                break

        # Area not found
        if area is None:
            packing_failed = True
            atlas_size = (atlas_size[0] + 64, atlas_size[1] + 64)
            print(f"Resizing atlas size to {atlas_size}")
            break

        # Split the area into new top and bottom areas
        x, y, w, h = area
        top = (x + sprite.width, y, w - sprite.width, sprite.height)
        bottom = (x, y + sprite.height, w, h - sprite.height)

        # Update the area list with the two new areas
        areas.remove(area)
        areas.append(top)
        areas.append(bottom)

    # Break the loop if we placed all the sprites
    if not packing_failed:
        print(f"Finished packing {len(sprites)} sprites")
        break

# Save the atlas file
atlas_file = Path("./atlas.png")
atlas.save(atlas_file)

# Save the sprite data file
sprite_data_file = Path("./data.json")
with open(sprite_data_file, 'w') as fp:
    json.dump(sprite_data, fp, indent=True)