Improved version of getimg.sh - gets the 'image of the day' from NASA, writes the summary onto the image and sets it as the Gnome wallpaper.

getimg.py

#!/usr/bin/env python
"""
getimg.py

Gets the current image of the day from NASA and sets it as the
background in Gnome. The summary / description text is written
to the image.

Requires:
    PIL             (apt-get install python-imaging or pip install PIL)
    feedparser      (apt-get install python-feedparser or pip install feedparser)

Christian Stefanescu
http://0chris.com

Based on the bash script of Jessy Cowan-Sharp - http://jessykate.com
http://blog.quaternio.net/2009/04/13/nasa-image-of-the-day-as-gnome-background/

intelli_draw method from:
http://mail.python.org/pipermail/image-sig/2004-December/003064.html
"""
import Image
import ImageDraw
import ImageFont
import urllib
import feedparser
import os
import commands

# Configurable settings
DOWNLOAD_FOLDER = '~/.backgrounds/'
FONT_PATH = '/usr/share/fonts/truetype/ubuntu-font-family/Ubuntu-B.ttf'
FONT_SIZE = 20
# how many empty text rows should be inserted to overcome top panel overlap
EMPTY_ROWS = 3

# Don't change stuff beyond this point
FEED_URL = 'http://www.nasa.gov/rss/lg_image_of_the_day.rss'
font = ImageFont.truetype(FONT_PATH, FONT_SIZE)


def get_latest_entry():
    """
    Get URL and description of the latest entry in the feed
    """
    feed = feedparser.parse(FEED_URL)
    return (feed.entries[0].enclosures[0].href, feed.entries[0].summary)


def download_file(url):
    """
    Get the latest NASA image of the day from the feed, returns the name
    of the downloaded file.
    """
    remote_file = urllib.urlopen(url)
    local_name = url.split('/')[-1]
    local_path = os.path.expanduser(os.path.join(DOWNLOAD_FOLDER, local_name))
    local_file = open(local_path, 'w')
    local_file.write(remote_file.read())
    remote_file.close()
    local_file.close()
    return local_path


def intelli_draw(drawer, text, font, containerWidth):
    """
    Figures out how many lines (and at which height in px) are needed to print
    the given text with the given font on an image with the given size.

    Source:
    http://mail.python.org/pipermail/image-sig/2004-December/003064.html
    """
    words = text.split()
    lines = []
    lines.append(words)
    finished = False
    line = 0
    while not finished:
        thistext = lines[line]
        newline = []
        innerFinished = False
        while not innerFinished:
            if drawer.textsize(' '.join(thistext), font)[0] > containerWidth:
                newline.insert(0, thistext.pop(-1))
            else:
                innerFinished = True
        if len(newline) > 0:
            lines.append(newline)
            line = line + 1
        else:
            finished = True
    tmp = []
    for i in lines:
        tmp.append(' '.join(i))
    lines = tmp
    (width, height) = drawer.textsize(lines[0], font)
    return (lines, width, height)


def write_description(img_file, text):
    """
    Write the given text to the given imagefile and overwrite it.
    """
    img = Image.open(img_file)
    (img_width, img_height) = img.size
    draw = ImageDraw.Draw(img)
    lines, tmp, h = intelli_draw(draw, text, font, img_width)
    j = EMPTY_ROWS
    for i in lines:
        draw.text((0, 0 + j * h), i, font=font)
        j = j + 1
    img.save(open(img_file, 'w'), 'JPEG')


def set_gnome_wallpaper(file_path):
    command = "gconftool-2 --set \
            /desktop/gnome/background/picture_filename \
            --type string '%s'" % file_path
    status, output = commands.getstatusoutput(command)
    return status

if __name__ == '__main__':
    if not os.path.exists(os.path.expanduser(DOWNLOAD_FOLDER)):
        os.makedirs(os.path.expanduser(DOWNLOAD_FOLDER))
    (url, text) = get_latest_entry()
    img_file = download_file(url)
    write_description(img_file, text)
    status = set_gnome_wallpaper(img_file)

@kroq-gar78: Have you tried changing the 'Style' setting in the Background preferences screen?

After having installed the Ubuntu font, it worked. However, the size of the images from NASA is always different, so that the caption isn't always in the same place.
I got back to the original script, and added a conky panel on my desktop.

NameError: global name 'drawer' is not defined on Ubuntu 12.04. Is there something I am missing?

After running the script, no change in the background image. --
No error in the terminal. --