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Pretorian
05-05-2005, 05:47 PM
Wich is the best way to select hair or how would you select hair?




Thanks

whookam
05-05-2005, 08:08 PM
If the hair is against a solid colour or there is a good contrast then probably the best method is to generate an alpha channel using colour and contrast masking, ie. convert the image to a high contrast grayscale and use it as a mask.

Sometimes the only way is to draw a mask, strand by strand! It takes a while though.

Pretorian
05-17-2005, 06:58 AM
I will try that and come back later if it don't work.



Thanks

morimitsu
07-06-2005, 11:22 AM
So, there isnīt a smart way/hidden secret to select hair?

I saw somewhere sometime ago a tutorial that teach how to select a monkey and composite/twick it so that the fur looks perfect after compositing with another background.
Now that I need it, I canīt find it anymore.
If someone know this tutorial, please, point it out.

Whipyo
07-07-2005, 01:33 AM
I'm not sure exactly what kind of image you are trying to apply this technique to but my method may help.....

First, create a clipping path around your object, keeping well inside your edge you want to mask. Load your path as a selection and click the add layer mask button (See attachmant - Pic 2).

Create a new brush by making a new document about 256x256 pixels or similar (you can make it larger if you want as long as it is square). Draw some random dots (see attachment - Pic 1). Select all and go Edit->Define Brush.

Using this newly defined brush, select the smudge tool and in the 'brush tip shape' tab in your brush pallete and set your spacing to 1%. In the 'other dynamics' tab, set the strength jitter to 0 and the control pulldown to fade. Select a suitable fade amount. This will depend on the size of your image, the size of your brush and the density of the hair you are trying to make. Just play around with this setting.

Using your smudge tool to work the edge of your mask. I use about the brush at 20-70% opacity and make bush strokes at different angles. Keep changing the brush size and the opacity so you get some variation. (See attachment - Pic 3).

You could also make a similar brush with the airbrush instead of the smudge tool. Just play with the fade settings. I usually find smudge to be good enough.

You should end up with something like my result (see attachment - pic 4). Keep in mind that my result is very rough, I just knocked up something rough in about 2 minutes. If you spend a but of time working the edge you can get some really good results that look natural. Obviously this wont work on an image with long flyaway hair etc.... It is a great technique for masking animals.

Good luck

Whipyo

PS. Sorry about the low quality of the pic....

lokki
07-07-2005, 04:10 AM
building on the suggestion to use a high-contrast grey image, here are some handy tips for creating a nice alpha channel. of course, this works best when pulling a subject out of a solid, flat background (e.g., studio shots)...

choose the best channel to start with from RGB or whatever mode you are working in. Sometimes, it might help to convert to LAB or other modes to see if you can't get better separation.

duplicate the channel (either to a new document or just an alpha channel depending on the situation), and duplicate it again in case you screw one up.

start by applying levels to the mask channel and see how far you can get there. maybe curves will help if you are dealing with a dynamic grey image.

use dodge and burn with various brushes. start with a round, semi-soft brush of small to medium size for hair. use a harder edge and bigger brush for long edges of cloth or skin. also consider using stipled brushes like in the example above for making whisps - just experiement.

fill large areas with the lasso tool or paint brush.

The idea is to get a solid black and white image with little to no grey or shading. Naturally, you should try the grey stuff just to see how it reacts, and it may actually be what you are looking for. Keep playing with it, and keep a 'clean' copy to go back to if necessary.

In the end, the selection is what matters, so use whatever is at your disposal. I've been known to composite many different channels, and even to build up masks by applying tweaks to the color image and then extracting a channel for use on the original. Don't forget that you can apply adjustment layers to your full-color image and go in to copy out a single channel (then remove the adjustment layer). Stack, build, play, whatever it takes.

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