Hi all,

I've just released a parametric masking plug-in for GIMP 3 and wanted to share it here.

The plug-in creates a layer mask from one of four source channels: Red, Green, Blue, or Luminance. You shape the mask using a tone curve with a live histogram. Drag points up to include tones, drag them down to exclude them. The canvas updates live as you work.

The curve approach gives you precise, automatically feathered control over the mask. Target midtones, create double peaks, or invert regions entirely. Since photographers already think in curves, there's no new mental model to learn.

The idea was inspired by Yasuo Ohnishi's slider-based parametric masking work for GIMP 3. My plug-in takes a different direction, using a curve editor instead of sliders.

A few highlights:

- Red, Green, Blue, and Luminance channel support
- Live preview on the canvas
- Whole-image mode and single-layer mode
- Non-destructive: works on a new layer, never touches the original
- Available in 14 languages
- Runs on Linux, Windows, and macOS

Full write-up with a short demo video: https://www.chuckhenrich.com/parametric ... mp-plugin/

Direct download: https://chuckhenrich.com/downloads/para ... ask-v3.zip

Happy to answer questions. Feedback and bug reports are very welcome.

A great plugin for those who enhance their photos in Gimp.

Question for the author:
How long does it take to write such an advanced plugin?

Thank you! It took me a couple of months. I had a lot of assistance from Claude Code AI. And it helps that I have 45 years' experience as a developer and product manager so I could get Claude to do what I want.