Selected plug-ins and tools which can be used with GraphicConverter

x3f_extract
This tool enables an alternative x3f import for some (not all x3f) variants. It is licensed under GNU General Public License on an as-is basis (i.e. without any type of guarantee).

ImageMagick 6.1.8 for Mac OS X 10.3.x
ImageMagick for Mac OS X 10.4.x or later
This plug-in enables the export of PCD (Kodak photo CD). ImageMagick is freeware which is offered without any type of guarantee. Further details are available on the official ImageMagick website.
Note: Please set the paths in GraphicConverter for the use of this ImageMagick distribution to /usr/local/bin/ . 

jbgtoppm command line tool
The jbgtopbm tool is licensed under GNU General Public License on an as-is basis (i.e. without any type of guarantee). The command line tool can be used to convert JBIG compressed data streams to PBM files.

MrSID V1.2 plug-in for GraphicConverter X | UB
The MrSID plug-in is freeware and is offered on an as-is basis (i.e. without any type of guarantee). This plug-in allows the opening of mrsid documents in GraphicConverter X (version 5.6 or later) and GraphicConverter UB (version 6.1.3 or later). The plug-in is based on the SDK licensed from Lizardtech. Click on the logo below to download products from Lizardtech and browser plug-ins. 

FFmpeg
The FFmpeg command line tool can be used by GraphicConverter 10.5.3 or later to decode HEVC data streams (i.e. to import a HEIC file on 10.9 to 10.12 which has no native HEVC support).

heiftobmps
The heiftobmps tool can import HEIC files on 10.9 to 10.12 (10.13 has native support for it). It can be used by GraphicConverter 10.5.3 or later.
The tool is based on the NOKIA sdk.

hqx upscaler
The hex tool can upscale pixel art.