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When Compositing Gets HairyA few tips for masking and compositing hair in Adobe Photoshop
In case you can't tell, that's sarcasm.
There's no easy or quick way to produce a mask on an image that contains complex hair. And yet, it is one of the necessary, common chores virtually all designers have to deal with at one time or another (unless you want your composite to look like an '80s-era TV Guide cover, which always looked like the subjects were cut out with dull scissors). I've had some pretty decent success with Extensis Mask Pro and Corel Knockout in the past, but even these dedicated masking tools can't solve every problem you will encounter when working with hair.
To make matters more difficult, you also have the problem of making your newly masked hair look "right" in your composite, a whole separate problem in its own right.
I've discovered and learned a few general techniques in Adobe Photoshop that can make masking out complex images a bit easier, but nothing that solves the problem entirely. Let's take a look at a few of these, as well as a quick tip on compositing the hair once you do manage to extract it.
Contrasting background layer
Whenever I get started on a masking project, I always create a new layer that I will use as a background to show through the portions of my image that I have already masked. This is particularly crucial for images with small details and subtle color gradations, where flaws in the mask might not be noticeable until you try to paste the masked image into your new composite. (For me, it's also much more useful than Photoshop's Quick Mask overlay, which can often get lost in a complex image.)
To do this, simply go to your Layers palette and create a new layer. Fill it with a bright color, such as yellow or orange or cyan, depending on the image you're working with. It should provide an obvious contrast the the colors in the original image. Then just move it behind the layer you'll be masking out. Voila! Instant feedback on the quality of your mask!
In some cases, you can complete a good portion of the masking process simply by generating a threshold on your image and using it as a "starter mask." In other words, it's not going to give you a perfect mask, but it's a good starting point.
To accomplish this, duplicate the layer you're going to be masking, then the choose Image > Adjustments > Threshold. Your layer will be converted into a black and white image, and you'll see a Threshold adjustment window pop up. Make sure your threshold contains all or most of the fringy hair in your image, even if part of the background gets picked up.
Once you've applied the threshold, go in and clean up the unwanted areas using the Paintbrush tool. And make sure you fill in all of the areas you want to keep with black. Then simply select the white or black areas of your mask and save your selection. (Optionally you can hold down the Command and Option keys while clicking on the "New Channel" icon in the Channels palette.)
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