Editing GIMP (section)

=== Layers, layer masks and channels ===
An image being edited in GIMP can consist of many [[Layers (digital image editing)|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.<ref>{{cite web |title=Introduction to layers |url=http://docs.gimp.org/2.6/en/gimp-image-combining.html#gimp-concepts-layers |website=Docs.Gimp.org |access-date=2 July 2009 |archive-date=7 October 2013 |archive-url=https://web.archive.org/web/20131007071617/http://docs.gimp.org/2.6/en/gimp-image-combining.html#gimp-concepts-layers |url-status=live }}</ref> Each layer in an image is made up of several channels. In an [[RGB color model|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 compositing|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.<ref>{{cite web |title=Layer Modes |url=http://docs.gimp.org/2.6/en/gimp-image-combining.html#gimp-concepts-layers |website=Docs.Gimp.org |access-date=2 July 2009 |archive-date=7 October 2013 |archive-url=https://web.archive.org/web/20131007071617/http://docs.gimp.org/2.6/en/gimp-image-combining.html#gimp-concepts-layers |url-status=live }}</ref>

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.<ref>{{cite web |title=Paths and Text |url=http://docs.gimp.org/ca/gimp-concepts-layer-modes.html |website=Docs.Gimp.org |access-date=16 February 2014 |archive-date=22 February 2014 |archive-url=https://web.archive.org/web/20140222133214/http://docs.gimp.org/ca/gimp-concepts-layer-modes.html |url-status=live }}</ref><ref>{{cite web |title=Text and Fonts |url=http://docs.gimp.org/2.6/en/gimp-concepts-text.html |website=Docs.Gimp.org |access-date=5 July 2009 |archive-date=7 October 2013 |archive-url=https://web.archive.org/web/20131007202529/http://docs.gimp.org/2.6/en/gimp-concepts-text.html |url-status=live }}</ref>

[[File:Droste Daisy.jpg|thumb|[[Droste effect]] using Mathmap plug-in]]