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Sunday, December 14, 2014

Part Two: Quick Tutorial for Skin Retouching with Wavelet Decompose script in GIMP

10:38 AM Posted by SnowSews
This is part two of the Interpreted Tutorial from TheCoffeeShopBlog.com, except that in this tutorial everything I describe is my own work. The original tutorial explains a Photoshop action which cannot be deployed in GIMP, so I found an alternate way to do things.

This segment deals with just skin retouching in Wavelet Decompose, although there are many other ways to do the job. I just liked the control I have over finer details here, giving subtle results and not making her look plastic, which I find is a frequent result when using Gaussian Blur methods. The next segments will deal with eye brightening, whitening whites, teeth whitening, sharpening and adding life to the hair, and boosting and adding vividness to the hair, eyes and lips. These are all steps in the original Photoshop action, but since we don't have access to that, these tutorials will have to do,

Please remember that I am a newbie, and these tutorials are mostly for me, since I tend to forget what I have learned very quickly. If they help anyone else, that's a big bonus.

I downloaded a script called Wavelet Decompose (not the plugin, couldn't figure out how to install that), and saved it in the gimp's scripts directory. Then I restarted GIMP, and could access the script from Image >Wavelet Decompose.

There are many detailed instructions on how to use Wavelet Decompose. The quickest, easiest way that I found was here. I just performed the following steps on the photo I edited in the previous blog post.


What the Wavelet Decompose script does is it splits the main layer into many layers, each with progressively sized details in grey scale, and one residual layer with the color. Each layer will recombine in the Grain Merge layer mode, thus building back up to the final image. If we remove a detail on a particular scale layer, it will be suppressed in the final image. 

I found this method to be particularly effective in removing uneven tone and shadowing from fine hairs on the face. You don't have to worry about what color to pick each time, and possibly painting over the shadows of the face with an inappropriate highlight color - which usually makes the skin look plastic. This method also helps the skin look glowy and fresh, terms often used in advertising makeup. That's a good thing, right?

Here are the steps to quick Skin Retouching:
  • Merge all the layers of the image into one.
  • Go to Image > wavelet decompose, and use the generic settings, at least until you are more comfortable with the choices. The picture is decomposed into layers, each with progressive detail in greyscale, and the last residual layer has most of the color. By hiding the residual layer you can see the actual detail instead of getting lost in the many colors. 
  • Working on the layer with the most visible flaws, using the eye dropper tool, pick a color of grey that is in the area of the perfect skin. Then using a brush with low hardness and the chosen foreground color, paint over the imperfections. 
  • Remember to unhide all the layers and zoom out often, to make sure you haven't erased any important details. If you have, click Ctrl+Z until you undo the mistake.
  • This method also is useful in subtly darkening eyelashes or eyebrows, since by picking a middle layer and a slightly darker grey in the region I want to paint over, I just paint feathery strokes to darken the hair. This will be barely noticeable in this method.
Once you are done, simply flatten the image.

The final image in this example looks glowy and misty, and on closer inspection it looks like I need to sharpen her hair and definitely work on the eyes. I would also probably need to intensify the vividness of the lips and hair and eyes. All these will be tutorials to follow.