digiKam - Professional Photo Management with the Power of Open Source
f.lux - f. lux is a piece of software for Windows, Mac, Linux, iOS, and Android that provides a blue light filter over your screen. Research suggests limiting our exposure to blue light in the hours before bedtime can help us fall asleep faster.
XnView MP - XnView is a free software that allows you to view, resize and edit your images. It supports more than 500 different formats!
CareUEyes - CareUEyes is an eye protection software for windows that comes with blue light filter, screen dimmer, and break reminder
FastStone Image Viewer - FastStone Image Viewer is a fast, stable, user-friendly image browser, converter and editor.
Redshift Color Temperature Adjuster - Redshift adjusts the color temperature according to the position of the sun.