GIMP
Open Source
GIMP stands for GNU Image Manipulation Program which is an opensource image editor program supporting almost every popular image formats.
Darktable
Open Source
Darktable is a free and open-source photography workflow application and raw developer.
Photopea
Free
Photopea is a free online image editor, that runs without plugins. It can both read and save PSD files.
RawTherapee
Open Source
RawTherapee is a cross-platform raw image processing program, released under the GNU General Public License Version 3.
photivo
Open Source
Photivo is a free and open source (GPL3) photo processor. It handles your RAW files as well as your bitmap files.
