Libvips

http://www.vips.ecs.soton.ac.uk/

VIPS is a free image processing system. It includes a range of filters, arithmetic operations, colour processing, histograms, and geometric transforms. It supports ten pixel formats, from 8-bit unsigned int to 128-bit complex. As well as the usual JPEG, TIFF, PNG, SVG, PDF, GIF and WebP images, it also supports scientific formats like FITS, OpenEXR, Matlab, Analyze, PFM, Radiance, OpenSlide and DICOM (via libMagick). Compared to similar libraries, VIPS is fast and does not need much memory, see the Speed and Memory Use page.