#! /usr/bin/python

## Fetch some public domain images, make a PNG of the key, and encode
## that in the Exif.Image.OriginalRawFileData tags of the images

import os
import glob
import random
import shutil
import md5
import sys
import zipfile

key = 'wilderness fishsticks'

srcdir = os.path.dirname(sys.argv[0])
exifblah = os.path.join(srcdir, 'image.cmds')

def system(cmd):
    ret = os.system(cmd)
    if ret:
        raise OSError('return value %d: %s' % (ret, cmd))

# Download war posters
if not os.path.exists('ww0207-43.jpg'):
    system('wget -r -D digital.library.northwestern.edu -A jpg -nd -l 2 "http://digital.library.northwestern.edu/otcgi/digilib/llscgi60.exe?mode=phrase&query=conserve&REGION=&SIZE=20&db=0"')
    os.unlink('robots.txt')

# Store the key
open('key', 'w').write(key)

# Make a PNG of it
f = os.popen('pbmtext < key | pnmtopng -compression 0')
key_png = f.read()

# Duplicate two photos
jpegs = glob.glob('*.jpg')
random.shuffle(jpegs)
for fn in jpegs[:2]:
    root, ext = os.path.splitext(fn)
    nfn = '%s.dup%s' % (root, ext)
    shutil.copy(fn, nfn)
    jpegs.append(nfn)
random.shuffle(jpegs)

bytes_per_photo = len(key_png) / len(jpegs)

zipf = zipfile.ZipFile('archive.zip', 'w')
for i in range(len(jpegs)):
    fn = jpegs[i]

    cmd1 = 'set Exif.Canon.0x0019 %d' % i

    offset = i * bytes_per_photo
    if i == len(jpegs) - 1:
        bytes = key_png[offset:]
    else:
        bytes = key_png[offset:offset + bytes_per_photo]
    bytes_str = ' '.join(str(ord(c)) for c in bytes)
    cmd2 = 'set Exif.Canon.0x0018 "%s"' % bytes_str

    # First set some defaults
    system('exiv2 -m %s %s' % (exifblah, fn))
    # Now apply our devious stuff
    system('exiv2 -M\'%s\' -M\'%s\' %s' % (cmd1, cmd2, fn))

    # Read it in
    contents = open(fn, 'rb').read()

    # Find the new file's md5 checksum
    checksum = md5.new(contents).hexdigest()

    # Make a new zip file entry
    zi = zipfile.ZipInfo(checksum + '.jpg')
    zi.compress_type = zipfile.ZIP_DEFLATED
    zi.external_attr = 0644 << 16L
    zipf.writestr(zi, contents)

    # We're done with this file
    os.unlink(fn)