digiKam - Professional Photo Management with the Power of Open Source
ShareX - ShareX is a free and open source program that lets you capture or record any area of your screen...
Photos on macOS - Photos keeps your images organized and accessible. Rediscover favorite shots with Memories. Access them on your devices with iCloud Photos.
Greenshot - Greenshot is a free and open source screenshot tool that allows annotation and highlighting using the built-in image editor.
XnView MP - XnView is a free software that allows you to view, resize and edit your images. It supports more than 500 different formats!
LightShot - The fastest way to take a customizable screenshot.