> + * This file is a modified port of Softglow plug-in from Gimp.
> + * It contains code from plug-ins/common/softglow.c, see that for copyrights.
>
> Is that correct?

Yes, this only uses the sigmoidal transfer math from that file, I
changed comment to be a bit more accurate.

> + sigmoidalInfo->explanation = "Desaturates image and applies
> sigmoidal transfer to luma.";
>
> This explanation is redundant with the plugin name, and "sigmoidal
> transfer" is meaningless to most whereas, again, your description in
> this email seems better!

I changed the filter explanation to be more informative. Patch attached.