planar.py

"""Render Amiga bitplane data at a given geometry, either layout.

Nothing on this disc carries a palette next to its pixels, so the renderer
defaults to a grey ramp: the question these images have to answer first is
*what shape is it*, and a ramp answers that as well as the real colours do.

  planar.py FILE OUT.png W H PLANES [sep|inter] [offset] [pad]

`sep`   -- all of plane 0, then all of plane 1 (this disc's `.img` layout)
`inter` -- the eight plane-rows of row 0, then those of row 1
`pad`   -- extra bytes between one plane and the next (0 on this disc)
"""
import sys
from PIL import Image


def unpack(d, w, h, planes, layout='sep', off=0, pad=0):
    bpr = (w + 15) // 16 * 2                 # Amiga rows are word-aligned
    px = bytearray(w * h)
    for p in range(planes):
        for y in range(h):
            if layout == 'sep':
                row = off + p * (bpr * h + pad) + y * bpr
            else:
                row = off + y * bpr * planes + p * bpr
            if row + bpr > len(d):
                return px
            o = y * w
            for xb in range(bpr):
                b = d[row + xb]
                if not b:
                    continue
                for k in range(8):
                    if b & (0x80 >> k):
                        x = xb * 8 + k
                        if x < w:
                            px[o + x] |= 1 << p
    return px


def save(px, w, h, out, planes):
    im = Image.frombytes('P', (w, h), bytes(px))
    n = 1 << planes
    flat = []
    for i in range(256):
        v = min(255, i * 255 // max(1, n - 1))
        flat += [v, v, v]
    im.putpalette(flat)
    im.convert('RGB').save(out)


if __name__ == '__main__':
    src, out = sys.argv[1], sys.argv[2]
    w, h, planes = int(sys.argv[3]), int(sys.argv[4]), int(sys.argv[5])
    layout = sys.argv[6] if len(sys.argv) > 6 else 'sep'
    off = int(sys.argv[7], 0) if len(sys.argv) > 7 else 0
    pad = int(sys.argv[8], 0) if len(sys.argv) > 8 else 0
    d = open(src, 'rb').read()
    save(unpack(d, w, h, planes, layout, off, pad), w, h, out, planes)
    print('%s  %dx%d %d planes %s @0x%X' % (out, w, h, planes, layout, off))