PT Photo Editor!

Paint.NET is a free image and photo editing software. It features an intuitive and innovative user interface with support for layers, unlimited undo, special effects, and a wide variety of useful and powerful tools. An active and growing online community provides friendly help, tutorials, and plugins.

XnViewMP is a free software to view, organise, convert graphics and photos files or to create slide show, contact sheet, HTML pages.

(Official description) Create incredible photos anywhere with all-new Lightroom CC and 1 TB of cloud storage. Get powerful editing features on any device in a new, easy-to-use interface.

digiKam is an advanced digital photo management application for linux/KDE, which makes importing and organizing digital photos a "snap". The photos are organized in albums which can be sorted chronologically, by folder layout or by custom collections.

Shotwell is an open source photo organizer designed for the GNOME desktop environment.

Paint (formerly Paintbrush) is a simple, ultra-basic graphics painting program that is included with almost all versions of Microsoft Windows. It opens and saves files as Windows bitmap (24-bit, 256 color, 16 color, and monochrome, all with the .bmp extension), JPEG, GIF (without animation or transparency), PNG (without alpha channel), and TIFF (without the multiple pages).

From high-precision light and color tools, to advanced clarity and dehaze settings, to the ability to create and save your own filters. Polarr is the ideal photo editor for bloggers, students, and photo professionals alike. Now with the ability to batch export your photos, adding watermark, and using keyboard shortcuts, Polarr Photo Editor is also the most efficient photo editing tool available on Chrome.

nomacs is a free image viewer for windows, linux, and mac systems, which is licensed under the GNU Public License v3. nomacs is small, fast and able to handle the most common image formats including RAW images. Additionally it is possible to synchronize multiple viewers. A synchronization of viewers running on the same computer or via LAN is possible. It allows to compare images and spot the differences (e.g. schemes of architects to show the progress).

Get ready to take your photos where no photo has gone before with Fotor.

gThumb is an image viewer and browser for the GNOME Desktop.