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Extractions and Selections

Extracting Hair

2004-10-14 12:45:43 PM oddballgeek [TotalFark]
Check the colour channels. if the hair stands out in one in particular, make a copy of that channel and choke up the colours using levels, threshold (very rough, last chance kinda operation) or the channel calculations in the image menu to work on it. basically what you are looking for is a channel that shows the difference between hair and background best and then a channel that differs most from the one you picked. using the add or substract mode can, if the source is good for it, yield amazing results that leave you with a full mask or a partial mask that requires nearly no manual work.

If it's not a solid background (for which I use the background eraser), I'll usually mask around the edges, but not bother trying to get all the individual strands. Just get a rough outline, going inside the edge of the hair. Then take the smudge tool - you can experiment with the strength and brush size - and smudge around the edges of the mask, following the hair direction. Again, you're smudging the MASK, not the image itself. Usually a few different brush sizes with a fairly strong setting, using small flicks around the edge, will do the trick.

It's how I did the hair for this ( ), if you want an example of what it looks like. Not perfect, but usually plenty good enough, especially against a varied background, and far less work than just about anything else in that situation.

Selecting with Alpha Channels

An alpha channel is just another channel of information separate from the regular color channels. In this case it's used simply to make a selection. Anything white is 100% selected, anything black is 0% selected and grays are partially selected.

The easiest way to use it is to right click on the image in your browser and select "copy". Then in photoshop select the "channels" palette and click on the create new channel button (second icon from the right at the bottom of the channel palette). Next hit ctrl-V to paste the copied alpha channel into the new channel. Then hold down the Control key and click on the alpha channel's icon in the channels palette. You'll notice a selection outline around the white parts of the alpha channel. Next select the layers palette and click on the background icon in the palette. Then you can hit ctrl-J to copy the selected parts of the image into a new layer.

That's it!

Different ways to select something in Photoshop by mumbling2myself

1: The lasso/marquee/etc. tools. You know, the ones with the marching ants. You should already know these ;)

2: The pen tool (aka paths)

  1. Using the pen, draw a line (really a set of bezier curves connected with anchor points) around the object you wish to select.
  2. The first pass with the pen doesn't have to be perfect - once it's there you can go back and add/delete points, move points around, and grab the 'handles' and alter the curvature of the line.
  3. In the layers pallette, click on the 'Paths.' Right-click on the path you made and click 'make path a selection.'

3: Quickmask (aka the best unused way to select stuff, dammit) Quickmask basically acts the same way as layer masks, but gives you a selection instead of a cut-out.

  1. Double-click on the 'quickmask' icon underneath the color indicator on the tools pallette. Click the bullet for 'selected areas'.
  2. Hit ctrl-Q to enter quickmask mode. I'm kidding. That exits the program. Don't do this. Hit 'q' with no modifying key to enter/exit quickmask mode.
  3. Use your brush to paint black (it shows up as 50% transparency red... weird, huh?) over the areas you want to select.
    (a). You can paint grays to select things partway. It's a weird concept, but if you're familiar with regular layer masks, it'll make sense. Basically if you paint a gray that's halfway between black and white, the selection you're making will have a 50% transparency.
    (b). You can feather your selection by blurring it with the regular old blur filter. This can be fun. Also, if you ever have a layer that needs all it's edges blurred, ctrl-click on it's layer icon in the pallette and then enter quickmask mode. The hard edged selection will now be a hard edged pinkish blob overlaying the layer. Blur that mofo, then use this selection to paste into a new layer (do it in a new layer because you don't want to lose all that sharp data in case your product looks like shiat... just turn off visibility on the original layer. If your result looks good, forget it's there.)
  4. To actually use the selection once you've painted it in, just hit 'q' to leave quickmask mode. You'll now see the old ants marching around your selection and can copy/paste/delete/fill/etc. at will. Ba- da-bing.