Editing a mask

Now you'll touch up your selection of the egret by editing the mask channel. It's easy to miss tiny areas when making a selection. You may not even see these imperfections until you view the saved selection as a channel mask.

You can use most painting and editing tools to edit a channel mask, just as you did when editing in Quick Mask mode. This time you'll display and edit the mask as a grayscale image.

1 With the Egret channel selected, click any eye icon (» ) appearing next to the other channels to hide all channels except the Egret channel (if necessary).

When only the Egret channel has an eye icon, the image window displays a black-and-white mask of the egret selection. (If you left all of the channels selected, the colored egret image would appear with a red overlay.)

Look for any black or gray flecks within the body of the egret. You'll erase them by painting with white to increase the selected area. Remember these guidelines on editing a channel with a painting or editing tool:

• Painting with white erases the mask and increases the selected area.

• Painting with black adds to the mask and decreases the selected area.

• Painting with gray values adds to or subtracts from the mask in varying opacity, in proportion to the level of gray used to paint. For example, if you paint with a medium gray value, when you use the mask as a selection the pixels will be 50% selected. If you paint with a dark gray and then use the mask as a selection, the pixels will be less than 50% selected (depending on the gray value you choose). And, if you paint with a light gray and then use the mask as a selection, the pixels will be more than 50% selected.

2 Make sure that the Egret channel is the active channel by clicking on the channel in the Channels palette. A selected channel is highlighted in the Channels palette.

3 Now make sure that white is the foreground color. (If necessary, select the Switch Foreground And Background Colors icon in the toolbox.) Then select a small brush in the Brushes palette, and paint out any black or gray flecks.

Selection in channel Painting out black or gray

4 If any white specks appear in the black area of the channel, make black the foreground color and paint those out as well. Remember that when you paint with black, you increase the masked area and decrease the selection.

5 Choose File > Save.

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