ImageMagick - ImageMagick is a software suite to create, edit, and compose bitmap images.
ImBatch - ImBatch is a batch image processor with a nice graphical user interface.
OpenCV - OpenCV is the world's biggest computer vision library
DVDVideoSoft Image Convert and Resize - Free Image Convert and Resize is a compact yet powerful program for batch mode image processing.
Cloudinary - Cloudinary is a cloud-based service for hosting videos and images designed specifically with the needs of web and mobile developers in mind.
Batch Image Resizer - Resize, crop, shrink, flip, exif-rotate, convert, enhance, process multiple pictures and photos with professional software! 120+ Actions, 30+ Image Formats