wiredfool

Imagemagick is really wonderful, except when it’s not.

~$ convert -density 200x200 -units PixelsPerInch test.png test.tif
~$ convert -units PixelsPerInch -density 200x200 test.png test.tif

These two commands do different things, the first gives 200 pixels per centimeter, the second gives 200 pixels per inch. (This with 6.1.7, I’ve seen a bug report for 6.2.x as well.)