Seamless Compositing


Sometimes you ll see an advertisement in a glossy magazine that you know has been Photoshopped. Non sequitur and neosurreal images are dead giveaways, and sometimes they are amazingly clever. The image might have a brilliant concept, dazzling colors, and a truly dynamic composition and be perfect in every way ”except for a few out-of-place edge pixels. It is unfortunate when a great work of commercial art is just short of perfection , especially when Photoshop has built-in bandages to cover every possible boo-boo.

Matting is the key to clean composites. When you select an image, the anti-alias programmed into the selection tool selects edge pixels. When you drag the selection onto another image, the stowaway edge pixels can t be seen until they reach their destination. When you see them, it s usually a row of one or two pixels that are significantly darker or lighter than the color behind them, as in Figure 22.7.

click to expand
Figure 22.7: The hand grenade on the top is surrounded by light-colored edge pixels. On the bottom, the edge pixels were removed by defringing.

You can easily eliminate unwanted edge pixels by using Photoshop s matting functions. The matting functions eliminate those nasty little fellows and blend your image into the layers beneath it. There are three ways to matte an image, and if your edge pixels are particularly stubborn, there s also a workaround that does the job every time.

To matte an image, it must be on an independent layer surrounded by transparency. The three options are as follows :

Defringe Choose Layer Matting Defringe, and enter a value in the dialog box that is displayed (see Figure 22.2 earlier in this chapter). Defringe is an effective method of eliminating the off-color edge pixels selected by the anti-alias because it replaces the color of the edge pixels with the colors of the nearby pixels on the layer.

Remove White or Black Matte Choose Layer Matting Remove White Matte or Remove Black Matte to darken the white edge pixels or lighten the black pixels. This is helpful if you are moving a selection from a white or black background to another background.

Workaround for Stubborn Edge Pixels If neither of these operations works to your satisfaction ”and sometimes you just can t eliminate enough of that edge ”here s a neat workaround:

  1. Select the image pixels on the layer by pressing /Ctrl and clicking the thumbnail.

  2. Choose Select Modify Contract. Enter the amount (in pixels) to contract the selection. View the edge close-up to see how far into the image the marquee has contracted. Undo and enter different values if necessary.

  3. Choose Select Inverse.

  4. Choose Select Feather, and feather the selection 1 pixel.

  5. Press Delete/Backspace to delete the edge. Or, choose Layer Add Layer Mask Reveal All to convert the selection into a layer mask that will conceal the edge pixels.




Photoshop CS Savvy
Photoshop CS Savvy
ISBN: 078214280X
EAN: 2147483647
Year: 2004
Pages: 355

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