GEGL Extract and Color Luminance Channel

GEGL Extracts the brightness channel from an image and colorizes and blurs it. This filter was inspired by Gimp/GEGL's "Bloom" and Pixelitor's "Extract channel" filter. It shows that GEGL has the ability to extract channels for non-destructive editing with blend modes.

Rules for filter to work

1. Filter requires an alpha channel

2. It is highly recommended you use the blend mode addition.

3.Gimp's layer blend modes will support an external glow effect on transparency. GEGL's layer blend modes will NOT support an external glow effect on transparency.

Here is a preview of me using the filter with Gimp's layer blend modes correctly to get an external glow effect.

OS specific location to put GEGL Filter binaries

Windows C:\Users<YOUR NAME>\AppData\Local\gegl-0.4\plug-ins

Linux /home/(USERNAME)/.local/share/gegl-0.4/plug-ins

Linux (Flatpak) /home/(USERNAME)/.var/app/org.gimp.GIMP/data/gegl-0.4/plug-ins

OS specific location to put GEGL Filter binaries

Windows C:\Users\USERNAME\AppData\Local\gegl-0.4\plug-ins

Linux /home/(USERNAME)/.local/share/gegl-0.4/plug-ins

Linux (Flatpak) /home/(USERNAME)/.var/app/org.gimp.GIMP/data/gegl-0.4/plug-ins

Compiling and Installing

Linux

To compile and install you will need the GEGL header files (libgegl-dev on Debian based distributions or gegl on Arch Linux) and meson (meson on most distributions).

meson setup --buildtype=release build
ninja -C build

If you have an older version of gegl you may need to copy to ~/.local/share/gegl-0.3/plug-ins instead (on Ubuntu 18.04 for example).

Windows

The easiest way to compile this project on Windows is by using msys2. Download and install it from here: https://www.msys2.org/

Open a msys2 terminal with C:\msys64\mingw64.exe. Run the following to install required build dependencies:

pacman --noconfirm -S base-devel mingw-w64-x86_64-toolchain mingw-w64-x86_64-meson mingw-w64-x86_64-gegl

Then build the same way you would on Linux:

meson setup --buildtype=release build
ninja -C build