Photo Editing Software for Linux
Krita
Krita is a professional free and open-source painting software created and maintained by artists. The main focus of the project is to create top quality painting tools that everyone can afford and enjoy. Krita features an OpenGL-accelerated canvas, colour management support, an advanced brush engine, non-destructive layers and masks, group-based layer management, vector artwork support and switchable customisation profiles.
Darktable
Darktable is a free and open-soource photo editing software created for photographers, by photographers. Darktable is specifically designed for non-destructive raw photo post-production editing. The Darktable development community is comprised of avid photographers that has a good understanding of real world problems, challenges, and workflows.
GIMP
GIMP is a free and open-source raster graphics editor developed by the Free Software Foundation (GNU). The software is a perfect fit for anyone looking for a free and open alternative to Adobe Photoshop. GIMP can be used for photo retouching, image editing and composition. The software is commonly know within the Linux community but is available under the GPLv3+ licenses for macOS and Windows as well.
ArmorPaint
ArmorPaint is a a free 3D painting software specifically designed for physically-based texture painting. With ArmorPaint, you can paint with fully procedural materials, build fill layers with material nodes and use brush nodes to create patterns and procedural brushes. ArmorPaint supports up to 16K texture painting in seamless fashion using high-end graphics cards, which produce stunning results.
XnView MP
A versatile and powerful photo viewer, image management, image resize developed by XnSoft. The XnView MP image viewer is a free software for macOS, Linux and Windows. The software consist of a photo viewer and a photo editor. With the photo viewer you can view browse photos in thumbnail, fullscreen and filmstrip view and compare images and manage EXIF, IPTC, XMP meta data. The photo editor can be used to resize, rotate and crop photos or adjust brightness, contrast and color while applying filters and effects to images.
Akira UX
Akira UX is a free an open-source graphic design software built with Vala and GTK. The application offers a fast approach to UI and UX Design, mainly targeting web designers and graphic designers. Akira UX is available for all major Linux distributions, and through the elementary OS AppCenter.
Pencil2D
Pencil2D is a simple, yet powerful 2D animation, drawing and painting application that lets you create traditional hand-drawn animation using both bitmap and vector graphics. Pencil2D is released as free and open-source software under the GNU General Public License and uses the Qt framework. With Pencil2D you can seamlessly switch between raster and vector workflows, allowing you to sketch, ink & paint on the go.
Shotwell
Shotwell is a free and open-source image manager designed to orginize personal photos on Linux and the GNOME desktop environment.
Universal Media Server
Universal Media Server is a free and open-source media server capable of serving videos, audio and images to any DLNA-capable device. The software is regularly updated and has more features than any other media server, including paid media servers. Universal Media Server supports streaming to consoles like PS3, Xbox One, Xbox 360 and TVs like LG, Panasonic, Philips, Sharp, Samsung, Sony, and Vizio.
Natron
Natron is a powerful Digital Compositor that can handle all of your 2D and 2.5D needs. Its robust OIIO file formats and OpenFX architecture is what make Natron the most flexible open source compositor for the visual effects community. Its interface and functionally are the same across all platforms such as MacOS, Linux and Windows. Natron has a powerful keying, roto/rotopaint, 2D tracking tools that are staple for all current film production project that requires visual effects.