extraction of girl

slipchuck · #1 06-01-2006, 09:57 PM

Hello everyone.
I have tried and tried to extract this photo from the background and have had satisfactory results, at best.
I know how to do it, but on this photo I can't get the hair to come with it without getting green with it.
It must be convincing, as it will just be a cutout, with no background to hide any flaws.
I tried channels and so far no good.
could someone please try this and walk me through how you got it?
please post results, and if possible close up of the extracted hair on a transparent background.

thanks

Mig · #2 06-01-2006, 11:59 PM

Chuck,

Sorry, but you won't be able to do this convincingly. Photoshop will only get you so far with this picture, so you have two options, where a combination of both would get you the farthest.

1) in whatever bg you use, make sure it's green around her head. That way you can camouflage where things wouldn't be picked up by the program. Basically this would involve selecting all of her hair and parts of the green that the comes along with it, instead of the other way around, which is how many might tackle the problem.

You can also maniplute the greens through painting on them and using blend modes, etc to further reduce the appearance of the greens and blend it into the new bg. The sample of the child has her hair not only blending into the green, but it's both soft and at the same time full of artifact that blends with the artifict and softness that exists in the green. Therefore, selection of the hair only is impossible. The only thing that separates the hair from the leaves are that the leaves have more texture and they're green. Otherwise there's nothing much to separate them, cept we know the red that is on her head is hair, and the green stuff in the bg is plant life.

2) paint her hair. You'd do this by painting strands. Basically it involves sampling and painting, repeating over and over again. It works but it's time-consuming.

good luck tho - too bad about the bg, cuz it's a cool pic.

Mig

bart_hickman · #3 06-02-2006, 12:49 AM

I'm not sure how good is good enough. As with most attachments here, this one has a lot of jpeg artifacts. Here's how I'd do it. Refer to the first attachment.

Start by understanding what it is that distinguishes her hair from the background. It turns out the color is the what's mainly different (luminance is not very different) and more specifically, the hue contains most of the difference. So in step 1 I extracted the hue channel.

In step 2, I sampled the orange hair hue and filled a new layer with that color, then subtracted it (difference blend mode). This makes the hair black and other parts of the image various other colors depending on how different their hue is from that of the hair.

In step 3, I used a channel mixer with coefficients 33,33,33 and monochrome box checked to convert the hue contrast into luminance contrast.

In step 4, I used a curve layer to amplify this contrast. At this point, you are beginning to see what will become the mask.

In step 5, I used some dodging, painting, and a little smudging to clean up the jpeg mess (your original shouldn't be nearly this bad.) Viola, I have my mask (from your post, I suspect you made it this far on your own.)

So now look at the second attachment for what I do with the mask. I drop the original image into a group, then apply the mask (have to invert it) to the group. I also have a white replacement background below the group because it's easiest to see the green contamination with that color. The third attachment show the basic, green-contaminated extraction on white.

On top of the original (in the group), I create a blank layer with blend mode Hue. Then sample the hair color and paint over the green areas. You can be fairly sloppy because the inner hair is already the same hue and the mask constrains your outward strokes.

The final attachment shows the decontaminated cutout on the white background, but it'll look correct regardless of background.

Use the pen tool or magnetic lasso to extract her body.

The extraction is pretty sloppy thanks to the jpeg artifacts, but I was mainly demonstrating the color fix--I could have actually gotten a finer extraction by carefully using the luminance info as well as the hue info using the same sample-subtract-channel mix-curve method, but it would have been more time-consuming because it would need to be done in sections. I try to avoid spending much time on a heavily compressed image.

Bart

RokcetScientist · #4 06-02-2006, 06:40 AM

I'm guessing this is a very useful exercise to hone one's pp skills. But wouldn't simply retaking that photo with the girl against a plain background be a loooot quicker and get you much better results?

Flora · #5 06-02-2006, 07:17 AM

Hi Chuck,

..I agree ...

Quote:

Originally Posted by Mig

Sorry, but you won't be able to do this convincingly. Photoshop will only get you so far with this picture...

Quote:

Originally Posted by bart_hickman

I'm not sure how good is good enough. As with most attachments here, this one has a lot of jpeg artifacts.

....and am curious ... may I ask how are you going to use "a cutout, with no background..." ?

Anyway, I also went for colour separation ... I used a Channel Mixer and a Hue/Saturation Adjustment Layers .. (Attachment 1) ... and I got a result very similar to Bart's (Attachment 2) ... Result that I then 'refined' (Attachment 3) to put on a solid colour background ... (Attachment 4) ....

Flora · #6 06-02-2006, 07:22 AM

Quote:

Originally Posted by RokcetScientist

I'm guessing this is a very useful exercise to hone one's pp skills. But wouldn't simply retaking that photo with the girl against a plain background be a loooot quicker and get you much better results?

....

Daviskw · #7 06-02-2006, 02:40 PM

Hi Flora

I have tried to duplicate your results along with bart's...lol.. no luck. Could you explain a little more your steps?... Maybe you are bart could point me to a tutorial or one of you could make one yourselves. You both do a very good job on hair.

Butch

Flora · #8 06-03-2006, 08:22 AM

Hi Butch,

thanks for your kindness!

In Attachment 1 you can see the values I used for Channel Mixer where I tweaked the Red Channel only.

In Attachment 2 the Hue/Saturation ones where I tweaked the 'Master' only.

In Attachment 3 ... my Red Channel (the one with the most contrast) immediately after the previous tweaks...

In Attachment 4 my Red Channel after increasing the contrast with the Levels...

Refine the mask and you are done...

Daviskw · #9 06-03-2006, 08:41 AM

Thanks for taking the time to explain Flora, lots of practice for me I see. I guess I’ll have to do it a few times. Experience is so important in these types of procedures. Obvious tweaks to some are head scratches to others…lol

Butch

Flora · #10 06-03-2006, 08:49 AM

Hi again Butch,

... it's always a matter of trial and error for me too ... and, in cases like this, I assure you I get to 'head scratches' quite often too...

Daviskw · #11 06-03-2006, 12:49 PM

Hey..figured a way…lol

I decided to try desaturating the color of the hair. Then combining with a 50 % gray scale layer set to difference as Bart did I got a fair mask that with a little fix up here and there did not do too bad with the hair.

Butch

mistermonday · #12 06-03-2006, 01:06 PM

Flora & Bart, excellent masking work!!
Here is another approach to consider. In LAB, the colors Green and Red are mortal enemies in the A channel. This means they can be very quickly and easily separated with a Z curve or by applying the A channel to itself in Overlay Blend Mode a couple of times. When you convert the resulting image back to RGB, you end up with two very good masking candidates - the Red and the Green channels. A combination of both can help in the tough spots.
Regards, Murray

slipchuck · #13 06-03-2006, 02:08 PM

thanks everyone so far.
As for answering the question "why not take another pic with a different background, it definately would be easier.
I wanted to work with this one, because I like tackling difficult jobs, as it teaches me more then anything.
I don't know everything about Photoshop that is for sure.
A challenge is what I enjoy!

As for the color of a background it is going on, the answer is white.
My girlfriend does digital scrapbooking at www.digitalscrapbookplace.com
I enjoy the challenges she throws me, and 95% of the time I can figure it out without outside help
the other 5% I reach out for help from good people like yourselves!

I need to learn more about channel masking. I went to the book store and wrote down the direction to do this from Scott Kelby's channels book.
Unfortunately, it did not work.
seems like most of the books out there use a simple color background and make it look like a peice of cake.

If someone could point me to a book that is as good or better then scott's,
it would be much appreciated. (I am a visual learner so it needs to relatively easy to follow, simular to scott kelby's books)

so thanks again for the great work out there, now I have to try some of your technics

cheers

randy

mistermonday · #14 06-03-2006, 03:03 PM

Randy, you definitely want to check out Photoshop Masking and Compositing by Katrin Eismann.
Regards, Murray

Mig · #15 06-03-2006, 09:34 PM

First off, just want to say what an incredible job some people did with the masking of the hair here - really excellent!

Randy, you asked about a book on channel stuff... the one I'd recommend is called Channel Chops. It's probably out of print, since it was written for a much earlier version of photoshop back in the late 90's. However, it still works for today's version. It's a very dry book, but that's the one I used to learn about channels and it's a fine book. You can pick it up on the net somewhere.

Good luck.

Mig