GIMP - GIMP is a multiplatform photo manipulation tool.
digiKam - Professional Photo Management with the Power of Open Source
Pixlr - Pixlr® makes it easy to transform everyday images into stunning works of art.
XnView MP - XnView is a free software that allows you to view, resize and edit your images. It supports more than 500 different formats!
Photoscape - high quality photo editing software, that enables you to fix and enhance photos.
Photos on macOS - Photos keeps your images organized and accessible. Rediscover favorite shots with Memories. Access them on your devices with iCloud Photos.