Perl script to change desktop background in GNOME

For some reason, I don’t like having the same background for an extended amount of time (as in, more than 15 minutes). Call me crazy, but that’s just how it is.

So when I bought my current laptop (Asus G1S), it came pre-installed with Windows Vista Ultimate, so I figured I’d give it a try. With the sidebar thing I found an widget that changed my desktop background every 15 minutes or whatever I liked. Hmm, cool enough, but I don’t like that sidebar, and for some reason Win Vista always seem to run awfully slow on my computers (maybe it’s just me abusing them).

Anyways, after a few days, I’ve had enough with Vista. So I decided to give good old Win XP SP2 a try on this brand new baby. After an install, things are flying like crazy, but nothing is changing my desktop background :\

After some checking around, it seems that in a vanilla XP, it ain’t possible to change the desktop background by command line or even by API as far as I found. So I was stuck changing it manually.

A few weeks ago, I’d had enough of Windows XP (as I always do after a little while). I downloaded Ubunty Hardy, installed it, and always I was happy when I saw the comforting GNOME desktop. Ahhh.

But still, my background isn’t changing by itself Must fix.
The “easy” solution (atleast in my head), write a perl script that manages it for me.

My starting point was this:

• All my wallpapers are in one folder.
• Not all images matches my desktop resolution.
• I don’t really wanna think about what resolution I’m running, I want the script to figure it out themself.

So, this is what I ended up with:

You need Image:Size to be able to use this script. If you’re running Ubuntu, just do:
sudo apt-get install libimage-size-perl

#!/usr/bin/perl
use Image::Size;## Set this to 0 if you don’t want this program to do anything
$go = 1;

## Desktop background changer for GNOME
## By Anders Østhus (grapz666+perl@gmail.com)
## 27-04-2008
##
## You are free to use and spread this code as you like
## If you are spreading this code, or hacking on it for your own use
## I would appreciate a e-mail about it, just so I know that someone
## is actually useing it for something.
##
## Usage: ./wallpaper.pl /path/to/wallpapers/

if ($go eq 0) {
exit();
}

## Some variable declarations
@files = ();
$dir = “”;
$dir = @ARGV[0];
$previmg = “”;
$wall = “”;

## If you want a different background color, you can chage it here.
$bgcolor1 = “#000000″;
$bgcolor2 = “#000000″;

## Get the current image
$previmg = `gconftool -g /desktop/gnome/background/picture_filename`;
$wall = $previmg;

opendir(BIN, $dir) or die “Can’t open $dir: $!”;

while( defined ($file = readdir BIN) ) {
if ( $file eq “..”) {
} elsif ( $file eq “.”) {
} elsif ( $file eq “Thumbs.db”) {
} else {
push(@files, $file);
}
}

## Find out what resolution we are running…
## Current resolution ends up in $tmpres[3]
$res = `/usr/bin/xrandr | grep ‘*’`;
@tmpres = split(/ /, $res);
@subres = split(/x/, $tmpres[3]);

## As long as the selected image is the same as the previous image
## we select a new one
while ($wall eq $previmg) {
$wall = $dir . @files[&getRand];
}

## Get the resolution of the image
my ($size_x, $size_y) = Image::Size::imgsize($wall);

## Sets the background image
$cmd = `gconftool -s /desktop/gnome/background/picture_filename “$wall” -t string`;

## If the image is the same resolution as the desktop, set it centered
## If the image is smaller than the desktop, we keep it centered
## If the image is larger than the desktop, we set it to scaled
if ($subres[0] > $size_x || $subres[1] > $size_y) {
$cent = “centered”;
}
if ($subres[0] < $size_x || $subres[1] < $size_y) {
$cent = “scaled”;
}
if ($subres[0] eq $size_x && $subres[1] eq $size_y) {
$cent = “centered”;
}

## Sets scaling option and background color(s).
## Also sets ‘draw_background’ to ‘1′, incase something has turned it off.
$cmd2 = `gconftool -s /desktop/gnome/background/picture_options $cent -t string`;
$cmd3 = `gconftool -s /desktop/gnome/background/primary_color $bgcolor1 -t string`;
$cmd4 = `gconftool -s /desktop/gnome/background/secondary_color $bgcolor2 -t string`;
$cmd5 = `gconftool -s /desktop/gnome/background/draw_background 1 -t bool`;

closedir(BIN);

## The function that returns a random image from the image array
sub getRand {
my $range = scalar(@files);
return int(rand($range));
}

And then I’ve just added this line in my crontab:

*/5 * * * * /home/grapz/devel/perl/wallpaper.pl /media/sda5/wallpaper/

This makes sure that this script runs every 5 minutes, every day of the week, every week of the month, every month of the year and so on.