gnome-background-xml.py

#!/usr/bin/python 

import os
import sys
from itertools import chain
from random import shuffle

HEAD_XML = '''
<background>
  <starttime>
    <year>2009</year>
    <month>08</month>
    <day>04</day>
    <hour>00</hour>
    <minute>00</minute>
    <second>00</second>
  </starttime>
'''

TAIL_XML = '''
</background>
'''

NODE_XML = '''
<static>
  <duration>%(duration)s</duration>
  <file>%(a)s</file>
</static>
<transition>
  <duration>%(transition_duration)s</duration>
  <from>%(a)s</from>
  <to>%(b)s</to>
</transition>
'''

def is_image(s):
    return s.endswith('.jpg') or s.endswith('.png')

def find_images(root):
    for path, subdirs, filenames in os.walk(root):
        for filename in filenames:
            file_path = os.path.join(path, filename)
            if is_image(file_path):
                yield file_path

def emit(a, b, duration, transition_duration):
    return NODE_XML % { 'duration'            : duration, 
                        'transition_duration' : transition_duration, 
                        'a'                   : a , 
                        'b'                   : b }
def pairs(xs):
    '''
    Break a sequence into pairs
    '''

    return zip(xs, xs[1:])

def main(options, args):

    images = list(chain(*(find_images(i) for i in args)))    

    shuffle(images)

    duration            = (24 * 60 * 60) / float(len(images))
    transition_duration = 5.0

    nodes = ( emit(a, b, duration, transition_duration) 
                 for a, b in pairs(images) )

    print HEAD_XML
    print "\n".join(nodes)
    print TAIL_XML

    return 0

if __name__ == '__main__':

    rv = main(None, sys.argv[1:])
    sys.exit(rv)