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imgflo is an image-processing runtime built on top of GEGL which can be visually programmed using

It is used by imgflo-server, which adds a HTTP API for image processing.

imgflo is pronounced "Imageflo(w)".



See ./



Note: GEGL itself is under LGPLv3.


The imgflo runtime implements the [FBP runtime protocol] ( over WebSockets. It also provides an executable that can load and run a FBP graph defined as JSON.

The runtime uses GEGLs native graph structure, wrapped to be compatible with FBP conventions and protocols:

  • All GEGL operations are automatically made available as imgflo components
  • Each imgflo process is a GeglNode
  • imgflo edges can pass data flowing between GeglPad

The edge limitation means that only ports with type GeglBuffer (image data) can be connected together. Other data-types are in GEGL exposed as a GProperty, and can currently only be set it to a FBP IIP literal. In the future, support for streaming property changes from outside is planned.

One exception is for the special Processor component, which is specific to imgflo. This component is attached to outputs which are to be computed interactively. Because GEGL does processing fully on-demand, something needs to pull at the edges where image data should be realized.

Deploying to Heroku

Configure. Flowhub user id is found in the Flowhub user interface (Settings or Register runtime)

heroku config:set
heroku config:set FLOWHUB_USER_ID=MYUSERID

Check the log that the initial registration was successful, and then save the runtime ID permanently

heroku logs

See "Run the runtime" for more detail

Developing and running locally

Note: imgflo has only been tested on GNU/Linux and Mac OSX systems. Root is not needed for any of the build.

Download it via git

git clone
cd imgflo


imgflo requires git master of GEGL and BABL, as well as a custom version of libsoup. It is recommended to let make setup this for you, but you can use existing checkouts by customizing PREFIX.

Install node.js dependencies. Only needed for tests

npm install

For Mac OSX, you must install Homebrew

Building dependencies from source (recommended on Linux)

You only need to build the dependencies once, or when they have changed. See 'git log -- thirdparty'

git submodule update --init
make dependencies

If you are on an older distribution, you may also need a newer glib version

# make glib # only for older distros, where GEGL fails to build due to too old glib

Installing pre-built dependencies (recommended on OSX)

If you use this option, you must specify RELOCATE_DEPS=true in the commands below.

make travis-deps


Now you can build & install imgflo itself

make install

To verify that things are working, run the test suite

make check


To start the runtime

make run GRAPH=graphs/checker.json

This should open Flowhub automatically in your browser and connect to the runtime.

If the browser does not open, and you get "Operation not supported", add NOAUTOLAUNCH=1. Then you need to copy/paste the "Live URL:" into your browser manually to connect.

Registering runtime

imgflo can automatically ping Flowhub when it is available.

  • Open Flowhub
  • Login with your Github account
  • Click "Register" under "runtimes" to find your user ID. Copy it and paste in command below

Set up registration


Finally, to run the runtime use. You can customize the port used by setting PORT=3322

make run

If successful, you should see a message 'Registered runtime' with the new id. You should save this, and on subsequent runs on same machine use this id.


In Flowhub, refresh the runtimes and you should see your new "imgflo" instance. Note: sometimes a page refresh is needed.

You should now be able to create a new project in Flowhub of the "imgflo" type, select your local runtime and create image processing graphs!