To create a channel mask by rendering Canvas can create a channel mask when you render a vector, group, paint, or text object. To create the mask, choose the Mask and Trans- parency options in the Render dialog box. Canvas will create a chan- nel mask that makes blank areas around and inside the objects transparent. When you make a new paint object by pasting a non-rectangular selection copied from an image, Canvas makes a channel mask to hide white pixels surrounding the selection. Preserving transparency in images You can select the Preserve Visibility checkbox in the Channels pal- ette to preserve transparency when you paint or apply filters to an image. The Preserve Visibility checkbox is available when you edit a paint object that has a visibility mask. A paint object has a visibility mask if it was created with a transparent background, or if you applied a visibility mask with the Add Visibility Mask command. If a paint object has an opaque background, the Preserve Visibility checkbox is dimmed and can’t be selected. To preserve transparency while editing an image When a paint object is in edit mode, select Preserve Visibility in the Channels palette. When the option is selected, you can paint and edit the image without affecting clear areas or reducing the transparency of partially transparent pixels. Channel mask from alpha channel Vignette Original
Canvas 8 Help: Selections and channels (30 of 32)                                                   Page #680