The primary function of an alpha channel, also referred to simply as a channel, is to store a selection you might want to use later. You can save multiple selections in a channel.
An alpha channel is a mask through which you can paint on, and apply effects to, an image. The alpha channel stores 8 bits of information per pixel, which means that each pixel can be assigned one of 256 (28) levels of gray — from 0 (black) to 255 (white). White areas of the channel are selected, and black areas of the channel are protected. Intermediate levels of gray are partially protected. For example, areas that are 50% gray will allow 50% of the brushstroke or effect to get through the channel to the image.
Alpha channels work like selections. Selections, however, are available only when working with the active image during the current session. You can save your selection, which creates an alpha channel. Channels remain inactive (for canvas control) until you load them to a selection. You can think of a channel as a dormant selection. For more information about selections, refer to Selections and Transformations.
Corel Painter lets you create up to 32 alpha channels. The channels are listed in the Channels panel, where you can select and control them. You can edit a channel in a number of ways and then load it as a selection.
Stored channels remain part of the file when you save in Corel Painter or Photoshop format. No matter how many times you work on a file, the channels are available whenever you need them.
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