#shading equalization

[sibaku]

Gimp plugin - Shading equalization filter v2

I posted some pictures about a filter I implemented to reduce those annoying changes in shading when taking photos of your line drawings (http://sibaku.tumblr.com/post/105012775655/illumination-correction-filter-i-usually)

I wanted to get it running on Windows, but C based plugins for Windows are horrible, at least getting them to run is. I managed to compile them but they crash... and I didn't want to spend more time on it...

Soooo I rewrote and extended it in Python. Which should run on all systems

You can get the plugin here: https://dl.dropboxusercontent.com/u/26437043/plugin/shadingEqualization.py

You only have to copy it into your gimp plugin folder (The main folder is located probably at your user folder. For more information see google or so, shouldn't be hard to find)

It will then be available at Filter->Enhance->Shading equalization

Probably the best way is to use the default strength value of 9

BTW, your image will be converted to grayscale

Only thing to beware of is: Python is really really slow for this kind of computation. The more or less straight port from C did slow it down like 10 times. I did some optimization and trickery to boost it a bit, but it's still below the unoptimized C code. An image about the size of 1000*1000 takes about 10-20 seconds (the unoptimized code was about 50 and did less). 2-3000 pixel images can take around 1-2minutes, so keep that in mind. Not sure if I can get that much more speed out of python without any 3rd party libraries such as numpy. But it works nice, so I think its alright. You usually don't need sketches in overly high resolutions.

This is an example image

This is the image after filtering

After this step, you can easily adjust the contrast/brightness or curves or something else to achieve the desired result. I chose not to try some automatic stuff, so everyone can tweak it to their liking. Here is the final result

The images you'll see now show the original on the left. My usual approach is fiddling around with curves until it looks ok, that is displayed in the middle. On the right side, the result of the new filter with some very simple curve manipulations are shown.

For some more examples, see below the fold :)

Some text:

I also found an older image I did, where I have a version I tried to fix per hand. Tried to crop out the same region, it's pretty close. Though a nicer result. Although lots of black regions will worsen the result, here it's still ok though

Now for some details:

Also, since this is the second version of the plugin I want to showcase that the results are quite improved now. The following images show the old plugin's result on the left and the new ones' on the right

If you would like to, try it out :) Maybe this is something you want, I always wanted it at least ^^

If you tried it out and notice anything weird/bad or have suggestions, just contact me here or at twitter @sibaku1

You can also tell me if you used and or liked it :D