New Filter: Constrained Sharpen


I have added a new sharpening filter to my testing folder.

It sharpens the image but restricts sharpening to local min/max to reduce halos. It is particularly good for upsized images and artwork.


WOW, looks good

(Alan Gibson) #3

Great minds think alike.

I’ve also implemented sharpening (or any operation) with output limited to the range of a local area of the input. This sharpens without overshoot.

A related operation sets every pixel value to either the minimum or the maximum of the local area.

These processes don’t overshoot, so they cannot cause clipping.

Details at Limit min-max


Limited USM:

Set L channel of LAB to min or max:

(Lyle Kroll) #4

May give it a try on my next edit, Iain. You do make great presets and am thankful for that. :slight_smile:


Or ‘simple minds seldom differ’ :wink:

Cheers. It’s good to know people are using my stuff.

(Melissa Newcomer) #6

That is an interesting filter. How can I use it? Not real good at GIMP.

[Play Raw] .. Shooting Into the Sun

It is part of the GMIC plugin. Are you familiar with that?

(David B Kettrey ) #9

lain, it’s good that you have made your filters available to us. Several of your filters are invaluable to me and are excellent for photo restoration. Many of them seem quite advanced and definitely provide specialized functions not found anywhere else. Thank you very much!


Thanks DB, I appreciate the feedback.

Which filters do you use the most?



I use your “RGB tone” and “CMYK tone” filters the most. On my windows 10 pc those filters only work with parallel processing Off. (Also for Hue lighten-darken). In parallel they crash. Maybe you can also make a boolean for parallel/auto in your “RGB tone” filter.

Now I use “Iain remove pattern” quite often.

Iain, thank you for your nice filters.

Favourite filters
Favourite filters
Favourite filters
(paul matthijsse) #12

Hello @Iain, your Iain’s fast denoise is my standard noise reducer, it works very well with Luma set to 0.30.
Thank you!

(David B Kettrey ) #13

You’re welcome, lain. I have put several of your filters in my Faves list:

Exfuse…brightens dark single exposures in a nice, HDR-like manner.
Constrained Sharpen…this new filter is now a must-have in my Faves. This filter shows great promise in being able to make edges more fine and crisp in a natural way without “exploding” the noise, IMO.
Easy Skin Retouch…very effective at smoothing away low-frequency blotchiness and unevenness in areas that should be smooth. The settings allow me to keep the fine grain or small details in those areas while smoothing away larger frequency “blotches” and unevenness. (Ironically, I’ve never used this filter on skin, yet…I’ve used it, instead, on areas such as skies and other areas that need to be smooth and even in the final repaired photo.)
Your various Noise Reduction filters are very effective and versatile. Your Ms NLMeans C Noise 2 filter provides a high-quality noise reduction. And your Multi Scale Smoothing filter is excellent at cleaning the noise and smoothing and restoring the “flow” and edges of wispy, curvy textures such as areas of hair, fur, etc.
Your Pyramid Processing filter, used in moderation, is good at bringing out details and features in images.
There are a few other of your filters in my Faves list that I did not mention or which I intend to make more use of in due time.


Favourite filters

Thanks for your feedback guys.

I thought I would share the love, so I started a new thread for your favorite filters, so developers can get some feedback and encouragement.

(Lyle Kroll) #15

Hope David moves constrained sharpen into the Details area since it’s that innovative and useful. Thanks again, Iain. :slight_smile:


I’ve moved it into the details folder (At least I hope I have, my internet updates are broken so I can;t check).

I also added a variable amount of overshoot if you can tolerate some halos.

(Lyle Kroll) #17

Verified that it’s now there, Iain. Sorry about your internet issues; I sympathize with your plight. lol


(Melissa Newcomer) #18

Yes I am with G’mic So I will find in in the filters or plugins?



It will be in the filters of the GMIC plugin under the Details menu