Phatch is a fantastic tool to process a large number of photos in the same manner. For example, I use it to shrink images to show on a digital picture frame. Unfortunately it has not been maintained for years, and it will not start on recent versions of Ubuntu. Here’s a workaround.
To make Phatch start again, edit the file
$ sudo vim /usr/share/phatch/phatch/lib/pyWx/wxPil.py
Find line 44 (press
44G in Vim) and append
size = wx_image.GetSize().Get()
Source: Debian forums.
I post this here so I can find it easily if I have to re-install my system. Maybe it helps others too.