GIMP (/ɡɪmp/ GHIMP; GNU Image Manipulation Program) is a free and open-source raster graphics editor used for image retouching and editing, free-form drawing, converting between different image formats, and more specialized tasks.GIMP is released under GPLv3+ licenses and is available for Linux, macOS, and Microsoft Windows.

Development
GIMP is primarily developed by volunteers as a free and open source software project associated with both the GNU and GNOME projects. Development takes place in a public git source code repository, on public mailing lists and in public chat channels on the GIMPNET IRC network.

New features are held in public separate source code branches and merged into the main (or development) branch when the GIMP team is sure they won't damage existing functions. Sometimes this means that features that appear complete do not get merged or take months or years before they become available in GIMP.

GIMP itself is released as source code. After a source code release installers and packages are made for different operating systems by parties who might not be in contact with the maintainers of GIMP.

The version number used in GIMP is expressed in a major-minor-micro format, with each number carrying a specific meaning: the first (major) number is incremented only for major developments (and is currently 2). The second (minor) number is incremented with each release of new features, with odd numbers reserved for in-progress development versions and even numbers assigned to stable releases; the third (micro) number is incremented before and after each release (resulting in even numbers for releases, and odd numbers for development snapshots) with any bug fixes subsequently applied and released for a stable version.

Each year GIMP applies for several positions in the Google Summer of Code (GSoC); to date GIMP has participated in all years except 2007. From 2006 to 2009 there have been nine GSoC projects that have been listed as successful, although not all successful projects have been merged into GIMP immediately. The healing brush and perspective clone tools and Ruby bindings were created as part of the 2006 GSoC and can be used in version 2.8.0 of GIMP, although there were three other projects that were completed and are later available in a stable version of GIMP; those projects being Vector Layers (end 2008 in 2.8 and master), and a JPEG 2000 plug-in (mid 2009 in 2.8 and master). Several of the GSoC projects were completed in 2008, but have been merged into a stable GIMP release later in 2009 to 2014 for Version 2.8.xx and 2.9.x. Some of them needed some more code work for the master tree.

Second public Development 2.9-Version was 2.9.4 with many deep improvements after initial Public Version 2.9.2. Third Public 2.9-Development version is Version 2.9.6. One of the new features is removing the 4GB size limit of XCF file. Increase of possible threads to 64 is also an important point for modern parallel execution in actual AMD Ryzen and Intel Xeon processors. Version 2.9.8 included many bug fixes and improvements in gradients and clips. Improvements in performance and optimization beyond bug hunting were the development targets for 2.10.0. MacOS Beta is available with Version 2.10.4

The next stable version in the roadmap is 3.0 with a GTK3 port.

Features
Further information: Comparison of raster graphics editors

Tools used to perform image editing can be accessed via the toolbox, through menus and dialogue windows. They include filters and brushes, as well as transformation, selection, layer and masking tools.

Color

There are several ways of selecting colors, including palettes, color choosers and using an eyedropper tool to select a colour on the canvas. The built-in color choosers include RGB/HSV selector or scales, water-color selector, CMYK selector and a color-wheel selector. Colors can also be selected using hexadecimal color codes as used in HTML color selection. GIMP has native support for indexed colour and RGB color spaces; other color spaces are supported using decomposition where each channel of the new color space becomes a black-and-white image. CMYK, LAB and HSV (hue, saturation, value) are supported this way. Color blending can be achieved using the Blend tool, by applying a gradient to the surface of an image and using GIMP's color modes. Gradients are also integrated into tools such as the brush tool, when the user paints this way the output color slowly changes. There are a number of default gradients included with GIMP; a user can also create custom gradients with tools provided. Gradient plug-ins are also available.

Selections and paths

GIMP selection tools include a rectangular and circular selection tool, free select tool, and fuzzy select tool (also known as magic wand). More advanced selection tools include the select by color tool for selecting contiguous regions of color—and the scissors select tool, which creates selections semi-automatically between areas of highly contrasting colors. GIMP also supports a quick mask mode where a user can use a brush to paint the area of a selection. Visibly this looks like a red colored overlay being added or removed. The foreground select tool is an implementation of Simple Interactive Object Extraction (SIOX) a method used to perform the extraction of foreground elements, such as a person or a tree in focus. The Paths Tool allows a user to create vectors (also known as Bézier curves). Users can use paths to create complex selections, including around natural curves. They can paint (or "stroke") the paths with brushes, patterns, or various line styles. Users can name and save paths for reuse.

Image editing

There are many tools that can be used for editing images in GIMP. The more common tools include a paint brush, pencil, airbrush, eraser and ink tools used to create new or blended pixels. The Bucket Fill tool can be used to fill a selection with a color or pattern. The Blend tool can be used to fill a selection with a color gradient. These color transitions can be applied to large regions or smaller custom path selections.

GIMP also provides "smart" tools that use a more complex algorithm to do things that otherwise would be time consuming or impossible. These include:

• Clone tool, which copies pixels using a brush
• Healing brush, which copies pixels from an area and corrects tone and color
• Perspective clone tool, which works like the clone tool but corrects for distance changes
• Blur and sharpen tool blurs and sharpens using a brush
• The Smudge tool can be used to subtly smear a selection where it stands.
• Dodge and burn tool is a brush that makes target pixels lighter (dodges) or darker (burns)

Layers, layer masks and channels

An image being edited in GIMP can consist of many layers in a stack. The user manual suggests that "A good way to visualize a GIMP image is as a stack of transparencies," where in GIMP terminology, each level (analogous to a transparency) is called a layer. Each layer in an image is made up of several channels. In an RGB image, there are normally 3 or 4 channels, each consisting of a red, green and blue channel. Color sublayers look like slightly different gray images, but when put together they make a complete image. The fourth channel that may be part of a layer is the alpha channel (or layer mask). This channel measures opacity where a whole or part of an image can be completely visible, partially visible or invisible. Each layer has a layer mode that can be set to change the colors in the image.

Text layers can be created using the text tool, allowing a user to write on an image. Text layers can be transformed in several ways, such as converting them to a path or selection.

Automation, scripts and plug-ins

GIMP has approximately 150 standard effects and filters, including Drop Shadow, Blur, Motion Blur and Noise.

GIMP operations can be automated with scripting languages. The Script-Fu is a Scheme-based language implemented using a TinyScheme interpreter built into GIMP. GIMP can also be scripted in Perl, Python (Python-Fu),or Tcl, using interpreters external to GIMP. New features can be added to GIMP not only by changing program code (GIMP core), but also by creating plug-ins. These are external programs that are executed and controlled by the main GIMP program.MathMap is an example of a plug-in written in C.

There is support for several methods of sharpening and blurring images, including the blur and sharpen tool. The unsharp mask tool is used to sharpen an image selectively — it sharpens only those areas of an image that are sufficiently detailed. The Unsharp Mask tool is considered to give more targeted results for photographs than a normal sharpening filter.The Selective Gaussian Blur tool works in a similar way, except it blurs areas of an image with little detail.

GEGL

The Generic Graphics Library (GEGL) was first introduced as part of GIMP on the 2.6 release of GIMP. This initial introduction does not yet exploit all of the capabilities of GEGL; as of the 2.6 release, GIMP can use GEGL to perform high bit-depth color operations; because of this less information is lost when performing color operations. When GEGL is fully integrated, GIMP will have a higher color bit depth and better non-destructive work-flow. GIMP 2.8.xx supports only 8-bit of color, which is much less than what e.g. digital cameras produce (12-bit or more). Full support for high bit depth is included with new actual Gimp 2.10 version. For accelerations OpenCL is available for some operations.

File formats

GIMP supports importing and exporting with a large number of different file formats, GIMP's native format XCF is designed to store all information GIMP can contain about an image; XCF is named after the eXperimental Computing Facility where GIMP was authored. Import and export capability can be extended to additional file formats by means of plug-ins. XCF file size is extended to more than 4 GB since 2.9.6 and new stable tree 2.10.x.

Specifications

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