added gimp as standalone article

wiki/gimp.md

@@ -0,0 +1,20 @@
+# GIMP
+
+[GIMP](https://www.gimp.org/) is a popular cross-platform program for editing pictures.
+
+## Setup
+
+The GIMP program can be installed from files found on
+[the official website](https://www.gimp.org/downloads/).
+Alternatively many [Linux](/wiki/linux.md) [package managers](/wiki/linux/package_manager.md) 
+package GIMP in the `gimp` package.
+
+## Usage
+
+This section addresses the usage of GIMP.
+
+### Scale Image
+
+An image that is already loaded into GIMP can easily be scaled down (or up) by selecting
+`Scale Image` under the `Image` tab.
+Alternatively the scale tool reachable via `Ctrl+S` can be used.

wiki/image.md

@@ -15,7 +15,7 @@ This entry also features medicinal image and visual formats such as DICOM.
 
 Editing images can be done by various image manipulation software.
 
-- [GIMP](https://www.gimp.org/) is a popular cross-platform program for editing pictures.
+- [GIMP](/wiki/gimp.md) is a popular cross-platform program for editing pictures.
 - [ImageMagick](/wiki/imagemagick.md) is another cross-platform software suite for creating and
 - editing (raster) images.
 - [upscayl](https://github.com/upscayl/upscayl) is an upscaler that can be used cross-platform.