Transparency effects with channel masks Channel masks let you add transparency to images without altering them permanently. A channel mask creates transparency without changing any pixels in an image. You can remove a channel mask to eliminate the transparency effect at any time. To make an image transparent To make parts of an image transparent — to eliminate the back- ground in a photograph, for example — you can create a channel mask from a selection. This procedure explains how to transfer a selection into a channel mask to make selected areas transparent. 1 Choose Image > Show Channels to open the Channels palette. Double-click the paint object to put it into edit mode. You can use various techniques to select the areas you want to be transparent: •   You can click the Wand tool to select similar colors through- out the image. If a photograph has a colored background, for example, click the background to select it. You can also use the Color Range command to make a selection. •   To soften the edges of the selection, you can use the Image > Select > Feather command. 2 Click the Selection button in the Channels palette to save the selection in a new alpha channel. In the alpha channel, white pixels correspond to the selection. (A partial selection produces gray pixels in the channel). Black pixels in the channel correspond to unselected areas of the image. To create transparent areas from the selection, you need to invert the channel. 3 Press Esc to deselect the selection in the image. Then, click the alpha channel in the Channels palette to make it active. Choose Image > Adjust > Invert. This reverses the white and black areas in the channel.
Canvas 8 Help: Selections and channels (28 of 32)                                                   Page #678