wavelet

Wavelet Decompose Script-Fu

christoph.traxler — Sat, 17 Jan 2009 16:12:58 +0100

This is a Script-Fu script for losslessly decomposing an image into different detail scales. This should be useful for photo post processing (for instance reapairing skin in portraits).

I first saw this function on the plugin "Wavelet Decompose" by marcor. (http://registry.gimp.org/node/11742 - This is also a good description on how image manipulation can benefit from wavelet decompositing.) I believe the Script-Fu script produces very similar results to marcor's plugin. (I did not use marcor's plugin for myself, so I can't really tell. But the description on the plugin is very good and I used it as a reference.)

Unfortunately I'm not familiar with installing plugins on a Windows system. But I wanted to use a wavelet decompose function on my Windows system. As I also wanted to learn Script-Fu, I thought it would be a cool idea to write a wavelet decompositing script by myself. It would also be a good reason to practice Script-Fu.

So this is my first Script-Fu script and I hope also useful submission to the GIMP registry. (At least for those who are not able to install Plugins on their Windows systems ;-P)

After installing this script (copy to your scripts-directory), you should find a new entry "Wavelet Decompose ..." in your Image-menu.

Maybe this script also runs on GIMP 2.4 or older versions. But I was testing it only on version 2.6. Please write a comment, if you ran the script on 2.4 or older without errors. Thank you!

Description on the parameters:

Minimum Scale:
Enter the pixel size of the smallest Scale (Scale 1). For instance the default value "1" shows only the sharpes available details on the Scale 1 layer. Enter higher values if you work on higher resolution photos.

Scale Count:
Enter how many layers of detail scales you want.

Scale Increase Factor:
This tells the script how many times the next scale should be larger (showing rougher details) than the previous.

Scale Constant Increase:
How many pixels should the details on the next scale be rougher than the previous scale.

Work on Copy:
This option creates a new image. If you disable this option the original image will be flattened and then the decomposition is done on the original image.

Wavelet decompose 0.1.2 Win 32 Binary

Francois_C — Mon, 12 Jan 2009 14:54:41 +0100

Windows 32 binary of the last version of this plugin written by "wavelet" Marcor ;)

Wavelet Sharpen-0.1.1 Windows 32 binary

Francois_C — Mon, 12 Jan 2009 14:26:09 +0100

A new Windows compilation of the last version of this fine plugin written by Marcor.
No console window. Compiled with LDFLAGS=-mwindos as usual.

Wavelet decompose

marcor — Tue, 18 Nov 2008 17:18:44 +0100

This plugin losslessly decomposes a layer of an image into layers of wavelet scales. This means that you can edit the image on different detail scales (frequencies). The trivial recomposition of the image can be done by GIMP's layer modes so you can see the results of your modifications instantly. Among the applications are retouching, noise reduction, and enhancing global contrast.

Wavelet scales

An image can be transformed into a set of wavelet scales. There are detail scales and one residual. The detail scales contain the image details of a their scale size. This means that scale 1 contains only image details of the smallest scale. Scale 2 details are larger and scale 3 details even larger (and so on). This image illustrates this:

This plugin computes these scales losslessly and creates a new layer for each one. The recomposition is the addition of all scales which is done by GIMP using the grain merge layer mode. You can then paint the scales with your favourite tool, using (128,128,128) as neutral colour (for the details, not the residual). Values below neutral darken, values above lighten. The most straightforward thing to do is to use the paintbrush tool with the neutral colour and use different brushes and opacities. That way you erase details.

Skin retouching

The problem with skin retouching is retaining skin detail but erasing spots and such. However, one might want to keep freckles in the face (see image below). Achieving this is very difficult when operating in the normal image space. The skin details such as pores and hair are very small, spots and pimples are larger. If you erase the larger spots (with an airbrush for example) you hide the skin details inside it. With wavelets you decompose the image into scales of different detail size. To state it simply: One scale will contain the skin details like pores, other scales contain spots. They are rather nicely separated. Look at the image with the wavelet scales above. The first scale contains pores and freckles (it's a small image indeed) and the second and third one the spots. The problem is not separating the details from the spots anymore but finding out in which scales they lie. This image (taken by +psv) has been edited using wavelet decomposition. One could have erased the freckles easily, but this natural face is beautiful because of them.

Noise reduction

The human eye easily distinguishes noise from image detail. Computers cannot. By decomposing the image into wavelet scales you can decide for yourself which parts are erased and you get the most high quality result. For example in image regions which are out of focus you know there can't be any image details on the pixel size (they are just blurred). So you can pick a brush and erase wavelet scales 1 and 2 in such places. Image details of greater size are untouched by this as you will notice.

Local contrast

If you change the residual scale instead of the detail scales you can change the brightness of the image or global contrast without affecting local contrast. This means that you can get image details back out of dark image areas in full local contrast. This works for overexposed areas as well. However clipped image details (beyond white or black) cannot be restored.

JPEG 2000

akkana — Tue, 30 Sep 2008 23:21:57 +0200

The wavelet/JPEG 2000 plug-in, written by Divyanshu Vats, from the 2006 GIMP Google Summer of Code wavelet project, mentored by Simon Budig.

It creates three plug-ins:
jp2: JPEG 2000 support
denoise: A noise removal plug-in
ihalf: Inverse halftoning -- remove halftones from printed images.

It requires the openjpeg library, available at: http://www.openjpeg.org/

I'm not sure what the license is (the code files don't say) but the COPYING file looks pretty free.

Wavelet sharpen

marcor — Mon, 29 Sep 2008 11:02:08 +0200

The wavelet sharpen plugin enhances apparent sharpness of an image by increasing contrast in high frequency space. The amount of unsharpness of the original image can be taken into account by adjusting the sharpening radius. As an option you can choose to sharpen the luminance (YCbCr) channel of the image only.

Features

Graphical user interface
Preview image
Option to sharpen luminance channel only
Selectable sharpen radius
Lossless image conversions

Description

The wavelet decomposition of an image results in multiple images with different frequency content. When amplifying the high frequency parts the recomposed image appears to be sharper than the original one. That way the frequency which should be amplified most can also be selected and a given unsharpness in the original image can be taken into account.

This GIMP plugin allows to perform this wavelet decomposition and allows the user to adjust the amount of sharpening and the radius of unsharpness in the original image. As an option you can sharpen the luminance channel of the YCbCr converted image only which reduces colour artifacts to appear (especially in noisy images). The sharpness of the colour contrast is not critical to the human eye.

Example

This picture was taken with the Nikon D80 and the Nikkor AF 50mm 1:1.8 lens fully open. Because the image is slightly out of focus and due to the wide apperture and aliasing the image is not quite sharp.

License

The plugin is distributed under the General Public License (GPL) version 2 and newer.