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wp_capozzi
02-09-2009, 07:40 AM
Does anyone know if there is a technique to determine color from a black and white image? I have some old photos of houses that I am modelling where I would like to make a best guess at what color they were originally painted. After searching around, nothing has turned up yet as far as software or techniques. I was guessing that since some known things are in the pictures, like green grass and blue sky, there might be a way to determine some of the other gray values based on that. hmm.

Thanks,
Bill C.

grimoirecg
02-09-2009, 08:23 AM
No, the shade of grey is based on tone. Two objects could have exactly the same tone and be different colours, and two objects with the same colour be different tones.
I there was a way of doing this it wouldn't be a secret.

BigHache
02-09-2009, 01:21 PM
There's a technique used when converting b/w films into color. I don't know how they do it, as grimoirecg mentioned, two distinct colors can have the same grey tone.

I'd research how they do it in older films. That technique has been around for some time so it can't be hard to find.

Wickster
02-09-2009, 01:44 PM
i'm not sure you can get the original color or what it used to be from a B/W photo. I do know you can colorized that part of the picture while adjusting the HUE to give it a color, which is what photo restoration guys do to color old B/W pictures.

Titus
02-09-2009, 01:59 PM
I don't know about coloring techniques but I use recolored for some projects:

http://www.recolored.com/

Wickster
02-09-2009, 04:05 PM
I don't know about coloring techniques but I use recolored for some projects:

http://www.recolored.com/
Wow, that looks like a really cool piece of app.

lwanmtr
02-09-2009, 05:11 PM
Looks neat..but colorized images always look bad..the color is unnatural because you dont get the different tones that exist on skin...havent seen one yet that makes me think that b/w images should be colorized...

grimoirecg
02-09-2009, 05:50 PM
He wants to know what the original colours were, and that's impossible from a B&W photo.
Of course anyone can guess what the colours might be and colourise it based on that.

lwanmtr
02-09-2009, 06:01 PM
Could always research when the house was built...most houses built in a given time period have similar paint styles

wp_capozzi
02-10-2009, 03:02 AM
Thanks for the replies. I had been going down the route of comparing b/w photos of buildings still standing to photos of the demolished houses and buildings to see if there is a similarity in tones to draw from. Most of the structures I'm trying to recreate that are now gone were built between 1880 and 1920, so that gives me a time period to search in for popular trends and available materials in this locale. I think it will be down to my best guess when it comes to texturing the models.

Thanks,
Bill C.

SBowie
02-10-2009, 06:25 AM
I think Recolored is based on the research described on this page:

http://www.cs.huji.ac.il/~yweiss/Colorization/

I was pretty sure I remembered testing a plugin a long time ago that used this method and seemed to work quite well on video, but I have not been able to locate it here. It might simply be an that I tried batching an early version of Recolored, too long ago now. :(

Titus
02-10-2009, 09:09 AM
I think Recolored is based on the research described on this page:

http://www.cs.huji.ac.il/~yweiss/Colorization/

I was pretty sure I remembered testing a plugin a long time ago that used this method and seemed to work quite well on video, but I have not been able to locate it here. It might simply be an that I tried batching an early version of Recolored, too long ago now. :(

That's great, they give the algorith's Mathlab code. I haven`t used Matlab in 14 years but certanly there`s a posibility of someone creating a plugin for premiere, SE, etc.

BigHache
02-11-2009, 09:24 PM
Bill, I have a similar dilemma ahead of me. I'm preparing research and gathering images to do some historic renderings of downtown Jacksonville c.1920s, and it's tough to find information going back to that point, let alone pre-1900.

I've resorted to collecting old postcards, but even that has been difficult to determine colors of buildings because the postcards use false colors. I've been able verify that by identifying buildings that are still standing, and seeing a completely different color on the printed postcard. Certainly they didn't paint a stone church red at one point then pressure wash the whole thing back to natural stone. But either way, 90+ year old postcards are pretty cool.

There might also have not been a multitude of paints available at that time, so you may be able to limit your color palette to a few field and trim colors anyway. There's also probably nothing to notate that a building had a natural finish either.

lots
02-12-2009, 12:31 AM
I've actually written a program that converts a black and white image, to color using a reference color image.

For example, lets say I had a black and white image of a beach and a color image of a similar beach. My program would calculate the luminance value of each pixel, compare it to the luminance values on the color image, and use the pixel color of the closest luminance value on the reference image. I might have done some interpolation between the pixels as well or multiplied the reference color by the b/w image's luminance value.. but i don't remember anymore :P

The color was far from perfect :) It kind of looked like those old black and white movies that had been converted into technicolor or something. The technique I used actually wasn't good in some settings, while it was great in others. It did pretty well on a picture of a rocky coast with a bird, but did pretty badly when it came to trees around a lake (too much blues and greens, so the colors came out desaturated)

Anyway, this type of conversion is pretty expensive (price wise), and GOOD algorithms can cost a crap ton of money :)

akademus
02-16-2009, 05:09 AM
I tried the app and must say it's really neat once you get a hold on it.

It can also be useful for preparing color maps and such. Thank you.