ImageMagick
ImageMagick is a software suite to create, edit, and compose bitmap images. It can read, convert and write images in a variety of formats (about 100) including GIF, JPEG, JPEG-2000, PNG, PDF, PhotoCD, TIFF, and DPX.
VIPS is a free image processing system. It is good with large images (images larger than the amount of RAM you have available), with many CPUs (see Benchmarks for...
VIPS is a free image processing system. It is good with large images (images larger than the amount of RAM you have available), with many CPUs (see Benchmarks for examples of SMP scaling, VIPS is also part of the PARSEC suite), for working with colour, for scientific analysis and for general research & development. As well as JPEG, TIFF and PNG images, it also supports scientific formats like FITS, Matlab, Analyze, PFM, Radiance and OpenSlide.
Batch processing Command line interface
image-editing image-resize graphics batch-processing image-converter command-line-interface