digiKam - Professional Photo Management with the Power of Open Source
CThruView Transparent Image Viewer - CThruView is a free transparent image viewer that allows mouse clicks to go through the image.
XnView MP - XnView is a free software that allows you to view, resize and edit your images. It supports more than 500 different formats!
PixelPerfect - Allows developers to put a semi-transparent image overlay over the top of the developed HTML and...
Photos on macOS - Photos keeps your images organized and accessible. Rediscover favorite shots with Memories. Access them on your devices with iCloud Photos.
Osiva - Osiva" is an acronym that stands for "Overly Simple Image Viewing