You can change the 400 in the file name to any number and that is how many pixels (the longest of the 2 dimensions) your picture will have. I t keeps the aspect ratio for most, if not all photos. It has worked for our team for a few years now to condense pictures for our scouting database.
All you have to do is drag the photos over the .exe icon and a command prompt opens and works its magic. The current one on my computer desktop is set to 1920, which produces a 1920x1080 picture (typical) and in a very small file size. Hope this helps. PM me if you have any questions or concerns