DVDVideoSoft Image Convert and Resize - Free Image Convert and Resize is a compact yet powerful program for batch mode image processing.
Sketch - Professional digital design for Mac.
Darktable - darktable is an open source photography workflow application and raw developer.
Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
Caesium Image Compressor - Compress your pictures up to 90% without visible quality loss.
Adobe Photoshop - Adobe Photoshop is a webtop application for editing images and photos online.