Convert pdf files to png

find -name "*.pdf" -print -exec pdftoppm -r 300 -freetype yes -aa yes -aaVector yes "{}" "{}" \;

find -name "*.ppm" -print -exec convert "{}" -resize 800x600 "{}.png" \;

rm *.ppm

use mmv to change the names


Notes:
- Remove duplicates
- Replace colors

ddrescue

Great to get every readable byte from old media. Packages from your disto.

Helper script:

#!/bin/bash
if [ -z "$1" ]; then
echo usage: $0 file
exit
fi
LOG_FILE=$1.log
BB_FILE=$1.bb
DEST_FILE=$1
/bin/dd_rescue /dev/fd0 -l $LOG_FILE -o $BB_FILE $DEST_FILE

Stereograms

Three types can be viewed without gadgets:

• Stereoscopic images: two pictures side by side;
• Autostereogram: Repeated texture, creates a 3D form;
• Wiggle-gram: uninteresting.

Stereoscopic images:
Nice intro: http://www.jrsdesign.net/cross_parallel_viewing.html
Cross-eyed training: http://www.eyetricks.com/3dstereo85.htm

Autostereogram:
Intro and many images: http://www.eyetricks.com/3dstereo.htm
(I recommend trying it in full screen)
DIY: http://linuxgazette.net/104/kapil.html
Animated: http://upload.wikimedia.org/wikipedia/commons/6/6c/Stereogram_Tut_Animated_Shark.gif

On Wikipedia:
http://en.wikipedia.org/wiki/Stereoscopy
http://en.wikipedia.org/wiki/Stereogram