Author Topic: Perfect Colorisation - possible technical breakthrough  (Read 2876 times)

Offline bugbear

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Perfect Colorisation - possible technical breakthrough
« on: Tuesday 12 August 14 12:03 BST (UK) »
A while ago (march) I posted about colorisation using painted layers and "overlay" mode in Gimp (instead of using duplicated-and-colourised layers).

http://www.rootschat.com/forum/index.php?topic=86634.msg5257755#msg5257755

Following some recent wonderful colorised images:

http://boredomtherapy.com/colorized-history-photos/

my interest in colorisation was renewed.

I had never fully understood overlay mode (although it seems to work beautifully), so I read the manual. It became apparent (I'm a mathematican and programmer) that overlay mode is purely mathematical. It's just a complicated formula. This led to a sort of important thought.

Given a colour image, it's easy (in virtually any package) to make a monochrome version of it.

I have written an imagemagick script that, given a colour image and mono image will

create the colorlayer that when used in overlay mode on the mono will recreate the colour image.

This means that, at least for self teaching purposes, it is possible to see what a perfect colorlayer would look like. As guidance, I think this is valuable in the extreme.

I have attached an example. To demonstrate it to yourself, go into Gimp and load the mono and the colorlayer as layers, with the colours on top. Set the color layer's mode to "overlay" and watch the magic.
 :)







 BugBear
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Offline bugbear

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Re: Perfect Colorisation - possible technical breakthrough
« Reply #1 on: Tuesday 12 August 14 12:44 BST (UK) »
I have experimented with degrading the "perfect" colour layer to see what detail is required to get good results.

I have posterised and blurred it, and then further flattened out detail in some areas. The result would still be a more than acceptable colorisation job.



 BugBear
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Offline hoobaloo

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Re: Perfect Colorisation - possible technical breakthrough
« Reply #2 on: Tuesday 12 August 14 13:52 BST (UK) »
Surely the purpose of colouring a photo is because there is no colour version in the first instance and if a picture is, as you say, turned to monochrome and the coloured with layer overlays taken from the original picture one might as well just use a scanner. I don't know how long your process takes but with creating a mask for each single colour component there must be a lot of masks and a considerable amount of time. I have coloured, by hand, your image in about 35mins and although the colours may differ as I already said one is normally colouring without the benefit of hindsight, regards, John.

Offline bugbear

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Re: Perfect Colorisation - possible technical breakthrough
« Reply #3 on: Tuesday 12 August 14 13:59 BST (UK) »
Surely the purpose of colouring a photo is because there is no colour version in the first instance and if a picture is, as you say, turned to monochrome and the coloured with layer overlays taken from the original picture one might as well just use a scanner.

Yes, that's true, of course.

As I said in my first post:

Quote
This means that, at least for self teaching purposes, it is possible to see what a perfect colorlayer would look like. As guidance, I think this is valuable in the extreme.

it's like practising solving crosswords with the answer at hand. It's pointless, but in reality, you can hone the processes that you'll be applying when doing a crossword "for real".

I was most surprised how saturated the colours in a perfect mask were, so I (for one) have learnt something.

 BugBear
BICE Middlesex
WOMACK Norfolk/Suffolk