Here is a list of useful open-source libraries dedicated to the programming of image processing algorithms, which you can download and use for free.


C++

logo_cimg The CImg Library is a popular, small, comprehensive, open source C++ toolkit for image processing. CImg stands for Cool Image : It is easy to use, efficient and is intended to be a very pleasant toolbox to design image processing algorithms in C++. Due to its generic conception, it can cover a wide range of image processing applications.
 logo_pandore Pandore is a C++ library of image processing operators. The current version contains image processing operators that operate on grayscale, color and multispectral, 1D, 2D and 3D images.
logo_opencv OpenCV (Open Source Computer Vision) is a library of programming functions mainly aimed at real-time computer vision, developed by Intel Russia research center in Nizhny Novgorod, and now supported by Willow Garageand Itseez.[1] It is free for use under the open source BSD license.
logo_population2 Population library is a scientific open source library dedicated to the processing, analysis, modelling and visualisation of 2D/3D images. Around a community project, its objective is to structure a reproducible and shared science in these fields.
Magick++2 Magick++ is the object-oriented C++ API to the ImageMagick and GraphicsMagick image-processing libraries.
logo_vips 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, for working with colour, for scientific analysis and for general research & development.

Java

logo_imagej ImageJ is a public domain Java image processing program inspired by NIH Image for the Macintosh.