1 With an image in edit mode, choose Image > Show Channels. 2 Create a new channel to use as a selection mask by doing one of the following: •   If you have a selection in the image that you want to cus- tomize by editing in a channel, use the Save command to create a channel from the selection; see “To save a selection in a channel” on page 33.667. •   To start with a “blank” alpha channel, use the New Channel command. Be sure to choose the Masked Area option under Color Indicates in the New Channel dialog box. 3 In the Channels palette, click the new channel to activate it. The channel appears shaded in the palette and the image changes to show only the channel. Now click in the left column of the first (composite) channel. The original image appears with a transparent colored “mask” on the image. The color mask indicates the areas that will be masked — not selected — by the channel. 4 Use painting tools or filters to edit the image in the channel. The changes you make affect the active channel only. 5 To make a selection with the channel, load the channel by choosing Image > Select > Load. Choose the channel name in the pop-up menu and then click OK. Channel masks Channel masks apply transparency effects to objects, including paint objects, vector objects, text objects, and group objects. A channel mask creates transparency in proportion to the luminance of its image. A channel mask is a grayscale image channel. Black pixels in a chan- nel mask produce 100% transparency in corresponding areas of the masked object. White pixels in a channel mask produce 0% transpar- ency in the masked object. Gray pixels in a channel mask produce partial transparency in the masked object. Darker grays produce greater transparency than lighter grays. Channel masks are powerful because they let you use painting and image-editing techniques to create transparency effects, and because a channel mask can be applied to any type of object. An object’s channel mask is the same size as its bounding box. You can detach or delete an object’s channel mask to eliminate the transparency effect. Canvas displays a shaded mask representing an alpha channel when the alpha channel and the composite channel are visible Shaded mask
Canvas 8 Help: Selections and channels (25 of 32)                                                   Page #675