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. “Paint.NET is free image and photo editing software for computers that run Windows. Started life as an undergraduate design project mentored by Microsoft. Image editor that is part of the KOffice suite for Linux. Because of this it can show real-time previews of filters and keep modifications live for as long as you want.” “ChocoFlop allows you to edit your photos or design stuff using Apple’s CoreImage technology. Possibly the only editor on this list with a worse name than GIMP. “From basic image retouching to complex effects, Phoenix delivers the key features of a desktop image editor with the simplicity and accessibility of a web-based application.” The only web/online app in the list that supports layers and masks. Without further ado, and in alphabetical order, some free apps that fit the bill: A curves adjustment tool lets you control color, color saturation, contrast, brightness, and black white points. These features let you selectively apply edits and filters to portions of the image that you control. Layers and layer masks (alpha editing).Can’t afford Photoshop? Can’t justify the expense? What do you need in a good photo editor anyway? To me, the absolute essential features necessary for any photo editing app are: