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 Post subject: G'MIC skin smoothing for portrait images
PostPosted: Fri Dec 20, 2013 5:43 pm  (#1) 
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Hello there,

I'm happy to present a new filter I've just added to the G'MIC plug-in for GIMP today. After a filters update, you will be able to find it at Repair / Smooth [skin].
Its purpose is to smooth people skin in portrait images. It is a quite complex filter as many different technical steps are involved, and you can finely tune each of those steps.
Here is a quick explanation of the whole thing.

First, here is how it looks when selected in the plug-in :

Attachment:
gmic_smooth_skin.jpg
gmic_smooth_skin.jpg [ 897.26 KiB | Viewed 11712 times ]


As I said, the filter works with distinct steps :

1. First, it tries to detect the skin pixels. To do this, it uses a specific skin detector that can be run in Automatic or Manual mode.
The 'Automatic' mode tries to detect the pixels automatically directly from their chromaticities. I have trained a simple classifier on a high number (millions) of manually labelized skin pixels in various portrait images. When the luminosity is quite standard, this works quite well.
Sometimes of course, the automatic mode fails, and so you can enter the 'Manual' mode where you can do the training by yourself, from samples pixels you suggest (and you can see a 'target' in the preview window that must be positioned to localize skin pixel samples).

2. Once the skin mask has been determined automatically or manually, you enter the second step, which is : soften the details. The filter uses a pyramidal decomposition of the image into several scales (very similar to what Wavelet Decompose does, for those who know it), followed by an smoothing process (isotropic or anisotropic) on the medium details scale (the one that contains most of the skin imperfections).

3. Optionally, you can boost the finest details scale by some gain parameters, in order to render a more sharper image at the end.

Once all those actions have been done, the filter recomposes the image from all its details scales, to render the result.
As you can see, this is a quite complex filter, and it possibly avoids doing a lot of tedious things manually. Of course, you won't have as much controls as if you do the whole pipeline manually, but you will be able to do those things very very quickly.

Here is an example of automatic skin smoothing (almost the default settings), with quite 'light' settings :

Attachment:
gmic_smooth_skin_all2.jpg
gmic_smooth_skin_all2.jpg [ 206.71 KiB | Viewed 11712 times ]


And the same, with more 'heavy' settings (but not the heaviest by the way!) :

Attachment:
gmic_smooth_skin_all.jpg
gmic_smooth_skin_all.jpg [ 209.25 KiB | Viewed 11712 times ]


So, I think this filter allows you to perform quite subtle changes in your images.

Any comments, suggestions or questions are welcome. I'm quite happy with how the filter performs right now, considering the fact that each step was quite challenging to code.
I hope you'll enjoy it !

David.


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 Post subject: Re: G'MIC skin smoothing for portrait images
PostPosted: Fri Dec 20, 2013 6:02 pm  (#2) 
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Nice one, thank you

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 Post subject: Re: G'MIC skin smoothing for portrait images
PostPosted: Fri Dec 20, 2013 6:25 pm  (#3) 
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I've already toyed with this preset David. One of the best degrungers I've run across. I usually use dup grain extract, merge down and set to Overlay and then apply that selectively; won't be doing that anymore. Thanks a heap. :)

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 Post subject: Re: G'MIC skin smoothing for portrait images
PostPosted: Fri Dec 20, 2013 9:47 pm  (#4) 
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It would be worth checking this filter, but my version of G'MIC (1.5.6.1 beta) does not have that filter. Even after you enable the update. :roll:

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 Post subject: Re: G'MIC skin smoothing for portrait images
PostPosted: Sat Dec 21, 2013 5:55 am  (#5) 
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It requires the 1.5.8.0 version (or later).


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 Post subject: Re: G'MIC skin smoothing for portrait images
PostPosted: Sat Dec 21, 2013 6:03 am  (#6) 
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Location: "Looking for my eraser" =P
Thanks David. :)

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 Post subject: Re: G'MIC skin smoothing for portrait images
PostPosted: Sat Dec 21, 2013 11:21 am  (#7) 
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very good results David

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 Post subject: Re: G'MIC skin smoothing for portrait images
PostPosted: Mon Dec 30, 2013 5:35 am  (#8) 
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Thx David,

In image test, the result seen in the preview and obtained are very different. :hoh

In the preview the result is fantastic, and desirable.
But the result is unsatisfactory, and away from the expected when based on preview. :(

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 Post subject: Re: G'MIC skin smoothing for portrait images
PostPosted: Mon Dec 30, 2013 6:08 am  (#9) 
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Akros, did you modify the preview zoom factor manually ?
If so, then no surprise that the resulting image is very different from what the preview window shows.
Otherwise, I'd be interested by a simple test case so I can reproduce the problem on my machine, and (eventually) fix it if possible.


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 Post subject: Re: G'MIC skin smoothing for portrait images
PostPosted: Mon Dec 30, 2013 5:11 pm  (#10) 
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Ronounours wrote:
Akros, did you modify the preview zoom factor manually ?

Well... Unlike other previews (Smooth thin brush / wavelets etc.), in the smooth skin image was very small in the preview ... I then instinctively widened. :roll: :oops:
Ronounours wrote:
If so, then no surprise that the resulting image is very different from what the preview window shows.
Otherwise, I'd be interested by a simple test case so I can reproduce the problem on my machine, and (eventually) fix it if possible.

I had used the default settings, and as in the preview manually changed the result was satisfactory, stopped by.
Unaware that information about the loss of equivalence between the preview and the result, if there was a manual change the zoom. :lame

With this new information, I went back to the same image and adjusted the setup parameters, and the result was excellent! :yes
Very good the option to apply the Smooth Skin in a selected area of ​​the image! :clap :bigthup

Thx a lot Ronounours! :tyspin

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