In addition to installing a library, GEGL also installs gegl - a binary/program that permits doing image processing from the commandline as well as an aid during development of GEGL operations.
Render a composition to a PNG file, the composition can be in GEGLs XML format or the one-liner friendly terser gegl-chain format.
$ gegl composition -o composition.png
The following is the usage information of the gegl binary, this documentation might not be complete.
usage: /home/pippin/src/gegl/bin/.libs/gegl [options] <file | -- [op [op] ..]> Options: -h, --help this help information --list-all list all known operations --exists return 0 if the operation(s) exist --properties output the properties (name, type, description) of the operation -i, --file read xml from named file -x, --xml use xml provided in next argument --dot output a graphviz graph description -o, --output output generated image to named file, type based on extension. -p increment frame counters of various elements when processing is done. -s scale, --scale scale scale output dimensions by this factor. -X output the XML that was read in -v, --verbose print diagnostics while running All parameters following -- are considered ops to be chained together into a small composition instead of using an xml file, this allows for easy testing of filters. After chaining a new op in properties can be set with property=value pairs as subsequent arguments.