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Complex hair selection

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  #11  
Old 01-17-2006, 06:35 PM
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I read through meok's method and it's pretty much the same as I did here using the LAB channels.

1) Duplicate the layer;
2) Run levels on the A and B channels marking the background as one extreme (black / white) and the hair as the other;
3) Use Image>Calculations to form a new channel by multiplying the modified A and B channels (have to invert one of them);
4) Make a new duplicate of the original image and apply this channel as a mask;
5) Run Levels on the mask until you get the best possible masking of the edge hairs (don't worry about the inner hairs);
6) Paint the mask to show all the hairs away from the edge;
7) The hairs are now separated from the background, problem now is the colours - take a paintbrush set to blending "Colour" and sample from the "good" hair and paint on the "blue" hair. Vary the sample to get a few differente hues;
8) Put in your new background.

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  #12  
Old 01-17-2006, 07:41 PM
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Cameraken Cameraken is offline
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Quote:
Originally Posted by Swampy
(see the great calculation tutorial above, Thanks, Ken!)
Ha Ha. Swampy. That wasn’t a tutorial. That was a complete Guess based on Meok’s method. I have read loads of things about calculations and still don’t understand it.

I understand how to use it. But I don’t understand which channels I should be using or Why and I don’t understand which blending mode to Choose. I guess it will come with practice.

Rô. Your picture looks great.
Using Russell Browns method (as I did in my first post here) some of the stray hairs look very ‘fat/thick’.

I will try your method.

I still think Leuallen’s method of changing the colour of the stray hairs to the colour of the new background Before making the selection makes a lot of sense.


Ken
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  #13  
Old 01-17-2006, 11:52 PM
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bart_hickman bart_hickman is offline
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For step 2, he multiplied the inverse of the red channel and the non-inverse of the blue channel. Both the red channel and blue channel were enhanced prior to multiplication. You could enhance them as needed (curve, channel mixer, etc..) to get good contrast. This can be done interactively using adjustment layers rather than layer arithmetic.

For step 4, he subtracted some percentage from the blue channel and replaced that with an equivalent percentage from the red channel. This works because the hair has roughly equal red and blue channels. Again, I found that the channel mixer was more interactive for this step--go to the blue channel, set blue to 20% and red to 80%.

Very educational.

Bart
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  #14  
Old 01-18-2006, 12:24 AM
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Hair selection using LAB

I simply converted the orig image to LAB and selected the B channel (most contrast) and duplicated it. Then using the Apply Image command, applied the B channel to itself in Overlay Mode. A simple levels adjust to boost the contrast and the mask was pretty well done. Like Ro, I painted away the blue in the edge hair. Regards, Murray
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  #15  
Old 01-18-2006, 01:27 AM
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Craig Walters Craig Walters is offline
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if i understand what you want, you want to remove the blue background, but save the blue highlights in the hair? is this right? that's how i read it, so i did this:

craig
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  #16  
Old 01-18-2006, 01:41 AM
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Flora Flora is offline
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Hi,

great tips and results!!!!

The problem in these extractions (plain flat colour background), for me, is not so much masking and extracting .... (here, because of the 'flyaway hair', I followed Russel Brown's excellent 'Advanced Masking' technique and I had a very acceptable mask in no time at all using duplicates of Green and Red Channels in RGB Mode.... ) .... but minimizing/removing the 'leftover colour cast' from the previous background around the edges of my selection.
As usual, there are many ways for doing this, but sometimes it can lead to a nearly complete desaturation, or a rather flat and 'monochrome' colorization ... and, in both cases, the natural difference in colour shades and highlights gets lost .....
I've been 'experimenting' with this and found that a combination of Hue&Saturation and Selective Colors Adjustment Layers helps a lot...
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File Type: jpg F_hair.jpg (99.2 KB, 142 views)
File Type: jpg SNAP-0069.jpg (34.9 KB, 94 views)
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  #17  
Old 01-18-2006, 01:52 AM
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Flora Flora is offline
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Craig,

it seems you posted while I was still writing my answer ....
Quote:
you want to remove the blue background, but save the blue highlights in the hair?
... actually, what superfrasky wishes is to get rid of the blue highlights in the hair after changing the background ....

P.S. I work with PS.
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  #18  
Old 01-18-2006, 10:01 AM
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I've just tried something different with this picture ...

No masking whatsoever (at least not in the conventional way)

I'm out of the house now, but if interested I'll explain later ...
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  #19  
Old 01-18-2006, 12:18 PM
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Craig Walters Craig Walters is offline
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flora,

i looked super's posts over again and i think you're right. when he said 'i cannot'' it could have meant 'i cannot because of a restriction from the boss or client' or 'i cannot because i dont know how to do this'. so, i wasnt sure. but, i believe you're correct.

and, you shld know by now that we ALWAYS want to know how you do things! as i've said before, you set the mark that we almost all aspire to, and certainly at least that i do. i even bought elements 4 to see if i couldnt approximate your examples a bit better and learn what all those words like 'transform' really are. so, yes, we want to know

craig
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  #20  
Old 01-18-2006, 05:02 PM
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Gary Richardson Gary Richardson is offline
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No masking. I'm intrigued Flora, do explain.
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