I had to do that just the other day - here's what I used:
ls *.jpg | xargs -l -i convert -resize "50%" -gravity Center
-pointsize 48 -fill "#fff" -draw 'text 0,0 "{}"' -fill "#000" -draw
'text 5,5 "{}"' {} thumbs/{}
You may need to tweak the size, pointsize, color, etc. I also had to
put "arial.ttf" in the path where imagemagick was looking for it.
(/usr/share/fonts/default/TrueType/)
"thumbs" is the directory I chose to output to (had to mkdir first).
Using xargs helps when you're dealing with thousands of files...
HTH,
Chris
