ImageMagick

ImageMagick is a free, open-source software suite written in C for creating, editing, composing, and converting bitmap images. It reads and writes a wide range of formats, including JPEG, PNG, GIF, TIFF, and PDF. It provides a command-line interface for image processing tasks and APIs for embedding the same functionality in applications. It runs on Linux, Windows, and macOS, and the README also lists an iOS build.

Command-line operations cover format conversion, transforms (resize, rotate, deskew, crop, flip, trim), compositing, montage, drawing and text, decorating with borders, gradients, blur, sharpen, threshold and tint effects, and image identification. More specialized features include connected component labeling, convex hull, Canny edge detection, Hough lines, mean-shift and Kuwahara filtering, discrete Fourier transforms, perceptual hashing, adaptive histogram equalization, color management with profiles, HDR images, and multispectral imagery up to 64 bands.

For scale and performance, it is thread safe with OpenMP-enabled algorithms. Some algorithms are OpenCL-enabled, and it supports mega-, giga-, and tera-pixel images. A distributed pixel cache can offload intermediate storage to remote servers. Default builds are Q16 HDRI. Q8 non-HDRI builds use less memory and can be made with --with-quantum-depth=8 --disable-hdri. As of 7.1.1-16, Open, Limited, Secure, and Websafe security policies are available, and the README strongly advises defining a policy before use.

Typical users are developers, web and graphics engineers, and researchers who need scripted batch image processing pipelines for large numbers of images or recurring jobs. Related projects mentioned include Magick.NET, Fred's ImageMagick Scripts, and a legacy version 6 branch.