a twitter thread reminiscing about bbses pre-internet got me thinking about this. does a good enough job of converting old .mac

macpaint-to-pgm.py

import sys

def shiftout(fout, bs):
    for b in bs:
        bb = b
        for i in range(8):
            if (bb >> 7) % 2 == 0:
                fout.write(bytes([255]))
            else:
                fout.write(bytes([0]))
            bb = bb << 1

if __name__ == '__main__':
    fdata = open(sys.argv[1],'rb').read()
    fout = open(sys.argv[2],'wb')

    fout.write('P5\n'.encode('utf8'))
    fout.write('576 720 255\n'.encode('utf8'))

    n = 640
    while n < len(fdata):
        by = fdata[n]
        if by >= 128:
            repeat = 257-by
            rdata = fdata[n+1]
            n += 2
            shiftout(fout, bytes([rdata] * repeat))
        else:
            repeat = by
            rdata = fdata[n+1:n+repeat+2]
            n += repeat + 2
            shiftout(fout, rdata)

    fout.close()