GIMP is a free program for such photo retouching, image composition and image authoring. Essentially it's the closest thing to Photoshop you can get for free.
Glimpse is an open source image editor based on the GNU Image Manipulation Program. The goal is to experiment with new ideas and expand the use of free software.Discontinued
The Glimpse editor has been discontinuedSource: https://glimpse-editor.org/posts/a-project-on-hiatus/
WidsMob Retoucher is an excellent photo retouching program, which is able to reduce image noise, portrait retoucher, film pack, adjust effects, fish eye effects, vignetting and more other features to photos with ease.