Phorest

Phorest is a simple application that lets you quickly change an image's (or several images') aspect ratio. It can also be used as a photo viewer.

The application places a selection area over every image to indicate the aspect ratio to be applied to each.

Phorest is not meant to resize multiple images simultaneously. In the final result, the size in pixels is the same; it's the aspect ratio that has changed.

The aspect ratio can be changed to any format you want. It's as easy as entering two numbers, like 16x9, 4x3, or 2x3.

Phorest lets you set certain parameters such as the minimum size needed for images to be recognized by the application, or if the results should contain EXIF information.