XnConvert - XnConvert is an easy image converter for graphic files, photos and images available on Windows...
ImageMagick - ImageMagick is a software suite to create, edit, and compose bitmap images.
Photopus Pro - Photopus Pro is an easy to use batch image processing to simplify the process to convert, add watermarks (text and image), resize, transform, touch-up, rename, and apply effects to your digital images.
OpenCV - OpenCV is the world's biggest computer vision library
Online Image Converter - Online Image Converter converts your BMP, JPG, PNG, GIF or ICO files quickly and easily.
Cloudinary - Cloudinary is a cloud-based service for hosting videos and images designed specifically with the needs of web and mobile developers in mind.