Manupulating Images and their Properties

gimpchannel — Functions for manipulating channels.
gimpcolor — Functions for manipulating color.
gimpconvert — Conversions between RGB, indexed, and grayscale modes.
gimpdisplay — Functions to create, delete and flush new displays (views) on an image.
gimpdrawable — Functions to manipulate drawables.
gimpdrawabletransform
gimpedit — Edit menu functions (cut, copy, paste, clear, etc.)
gimpfileops — File operations (load, save, etc.)
gimpfloatingsel — Functions for removing or attaching floating selections.
gimpgrid
gimpguides — Functions for manipulating guides.
gimpimage — Operations on complete images.
gimplayer — Operations on a single layer.
gimppaths — Operations related to paths.
gimppixelfetcher — Functions for operating on pixel regions.
gimppixelrgn — Functions for operating on pixel regions.
gimpregioniterator — Functions to traverse a pixel regions.
gimpselection — Functions for manipulating selections.
gimptexttool — Functions for controlling the text tool.
gimptile — Functions for working with tiles.
gimptools — Access to common toolbox tools.
gimpundo — Control of undo/redo.
gimpvectors