GIMP is a multi-platform photo manipulation tool. GIMP is an acronym for GNU Image Manipulation Program. The GIMP is suitable for a variety of image manipulation tasks, including photo retouching, image composition, and image construction.
GIMP has many capabilities. It can be used as a simple paint program, an expert quality photo retouching program, an online batch processing system, a mass production image renderer, an image format converter, etc.
One of The GIMP’s strengths is its free availability from many sources for many operating systems. It is not as good as Adobe Photoshop, but it’s a lot cheaper so is a good alternative if your budget doesn’t stretch far enough.
GIMP Official Tutorials