amos-abk

A Python library for loading AMOS .abk bank files from the Amiga.

Parses the container format and three image bank types:

• Sprites — hardware sprite images with hotspot and transparency
• Icons — software bob images (same format as sprites)
• Pac.Pic. — packed full-screen pictures with three-stream RLE compression

Non-image banks (Music, Samples, Amal, Datas) are loaded as raw DataBank objects.

Binary stream inputs are consumed from their current position through EOF; they do not need to support seeking. Caller-owned streams remain open.

Pac.Pic. colour conversion supports indexed screens and six-plane Extra Half-Brite (EHB). HAM, dual-playfield, and other unsupported high-depth modes raise ValueError during RGB/RGBA conversion (OSError through Pillow). Their raw bitplanes and indexed values remain available for custom decoding. Sprite and icon colour conversion supports up to five bitplanes (32 colours). Higher-depth images retain raw/indexed access but reject colour conversion: these banks do not store the screen mode needed to interpret those colours.

Links

• 🏠 home
• 📚 pydoc
• 🐍 pypi
• 🐱 github

Install

pip install amos-abk

Library usage

from amos_abk import load, parse_sprites, parse_packed_picture

# Load a bank file
abk = load("sprites.abk")
print(abk)  # AbkFile([Sprites])

# Parse sprites and convert to PIL Images
sprites = parse_sprites(abk.banks[0].data)
for i, sprite in enumerate(sprites):
    sprite.to_image().save(f"sprite_{i}.png")

# Parse a packed picture
abk = load("picture.abk")
pic = parse_packed_picture(abk.banks[0].data)
pic.to_image().save("picture.png")

# Access raw data
print(pic.width, pic.height, pic.num_planes)
print(pic.palette[:4])  # first 4 RGB tuples

Pillow plugin

import amos_abk registers a Pillow plugin, so you can open .abk files directly:

from PIL import Image
import amos_abk

img = Image.open("sprites.abk")
img.save("first_sprite.png")

# Multi-frame: seek through all images in the file
for i in range(img.n_frames):
    img.seek(i)
    img.save(f"frame_{i}.png")

# The parsed AbkFile is available in metadata
abk = img.info["abk"]
print(abk.banks[0].name)

Extract all images

The images() function extracts every image from every bank in a file:

import amos_abk

# From a file path
imgs = amos_abk.images("sprites.abk")
for i, img in enumerate(imgs):
    img.save(f"image_{i}.png")

# Or from an already-loaded AbkFile
abk = amos_abk.load("sprites.abk")
imgs = amos_abk.images(abk)

Format overview

AMOS was a game-creation environment for the Amiga, released in 1990. It stored graphics and other resources in .abk memory bank files.

Bank container

Each .abk file contains one or more banks, either bare (AmSp/AmIc magic) or wrapped in an AmBk header with a bank number, name, and memory type. Bank sets (AmBs magic, usually .abs files) hold a count followed by any mix of these.

Sprite and icon banks

Sprites and icons share the same format: a count, per-image headers (dimensions, bitplane count, hotspot), interleaved planar bitmap data, and a shared 32-entry 12-bit Amiga palette.

Pac.Pic. banks

Packed pictures are compressed full-screen Amiga images. They have two layers:

1. Screen header (magic 0x12031990) — dimensions, display window, flags, and palette
2. Packed bitmap (magic 0x06071963) — three-stream RLE compression where POINTS controls RLEDATA, and RLEDATA controls PICDATA

License

WTFPL: do as you like, but don't blame me if it banks your sprites.