Hi there,

I'd like to present a new color filter I've made for the G'MIC plug-in, located in 'Colors / Recolorize'. It should be available after a filter update. The principle is quite simple. Imagine you open a B&W image in GIMP :



Now, create a new top layer (with transparent background), and draw some color patches on it :



Now, open G'MIC, select 'All layers' for the 'Input Layers' mode, and select filter 'Colors / Recolorize' :



This filter tries to extrapolate your color patches in a quite smart way (edge-directed), so that your color patches are extrapolated over all the image area. It recomposes then the initial B&W image and the color patch so that you get a color image at the end, where the lightness of the resulting image is exactly the same as your original B&W image :



I'm sure there are a lot of funny things we can do with this kind of filter. Any ideas of use or suggestions for improvements ? Feel free to test and tell me if you find it useful !

Cheers.

COOL !!

1)
Once the colours to use are determined how are applied to the original BW image ?

Something similar to color mode ?
or swapping images positions, to Value or luminosity mode ?



I may ask a favour ? i would like try to modify to include a alternative :
the lightness would be only close no more identical to the original BUT the colours would looks more ... natural ? catchy ? hard to find the word i should include a example

To do this would be of great help the part of code TILL the merging (before the colour image are applied on the bw)

Yes , i know i may already look to your code but ...you write in a very optimized way with large use of shortening that make the code more compact and efficient but much harder for me to decipher

The first impression is very positive,filter works fast and it looks really well.Thanks.
More of tests later.

Original image B&W http://img0.liveinternet.ru/images/atta ... 713001.JPG

Wow Pogo, did you really use the G'MIC Recolorize filter to get this result ? If so, I'm stunned !
I would be very interested to see the image of the color patches then.

Humm
this is your code...
i really can not find where the colors are applied to the desaturated original

my idea was just allow to modify the merging ..but where is the merging step ?

Yes,it's true.lol
xcf file in the Annex

@PC : Basically, this is a similar implementation to the plug-in 'Colorization', already discussed here : viewtopic.php?f=9&t=839&start=0.

But as the Colorization plug-in is not maintained anymore, I think this is cool to have such a feature in G'MIC (especially as it will be easy to maintain, it took only about 10 lines of G'MIC code :p).

The color extrapolation works by extrapolating the chromaticity values of the colors in Lab. I've some ideas for improvement :
- Ability to select the output mode, either as a single RGB image (as it is done now), either as two layers that should be blended in 'Color' or 'Value' mode, so that we can correct the color extrapolation on some regions where artefacts remain.
- Ability to select amongst several color spaces for the extrapolation : either Lab (as it is done now), but also YCbCr and RGB, with or without keeping a strict lightness constraint.
Maybe I'll have time to do this tomorrow.

@Pogo : so you made my day, definitely :p Thanks a lot for this fantastic result.

Thank you for uploading your file! Checking your method was very helpful.

very nice result pogogogo !

yes a very nice idea indeed


I really like the results ( i make a quick confront with colorize..nothing worth to be posted but result were good



That would be perfect for what is spinning in my mind

I never found written references for this but i get often result i like more by

1 )Slightly blurring the "color" layer (except with unreasonable dramatically high values this do not make the resulting image less sharp, but somehow make more clean )
2 )Slightly sharpening and darkening the grayscale layer
(this instead impact a lot on result sharpness )

i do this almost always when using value or color modes,
not always but often i also create additional dup of the layer used , and i add to the visible once merged with low opacity in soft light or overlay mode (to make colors more brilliant and/or increase shadows/highlights contrast )

Again i have no references for this... just my own experiments

Bonjour,

@Ronounours
Thank you, it will not be necessary to use the old filter "colorize"

Very Cool, quick try

Impressive indeed Pogo and thanks for sharing the cool preset David.

Thanks to all for the nice comments.

Wow pogo, that is fantastic. I tried it with Carrie Underwood and mine was a mess. Gots to go back and start from scratch.

A bit of play with, Recolorize.
The only difference is the method to isolate the lines.
Inverse edge detection is one interesting method.

Nice Filter! I will have to download the new G'mic for sure and try it. That is really a great photo Pogo.

Nice experiment and result Odin.

I've implemented a new 'output mode' for this filter, that split the result into two Value / Colors layers, so that it is easier to tweak the color layer afterwards (correct some glitches for instance). Set the top layer to 'Value' blending mode to render the colored result.