Apple MA434Z/A User Manual - Page 414

Parameters This node displays the following control in the Parameters tab: outBytes Forces the incoming image into a new bit depth. There are three buttons, corresponding to three values in the outBytes parameter field. • 1 = 1 byte per channel, or 8 bits per channel. • 2 = 2 bytes per channel, or 16 bits per channel. • 4 = 4 bytes per channel, or 32 bits per channel (float). Channels Explained Shake supports and tracks different numbers of channels in an image in your composition, giving you channel independence as well as bit-depth and resolution independence. For information on displaying different channels in the Viewer, see "Using and Customizing Viewers" on page 45. Code BW (Black and White) A (alpha) Z (depth) BWA RGB RGBA Description 1-channel grayscale image. 1-channel matte image. 1-channel depth image, always in float. 2-channel grayscale image with matte channel. 3-channel color image, representing Red, Green, and Blue information. 4-channel color image with matte channel. An additional Z channel can be added to any of the above, so the maximum number of channels you can use to represent a single image is five: RGBAZ. Unfortunately, the Z channel does not show up in the Viewer unless you use the View Z script button. (Whether or not the View Z script is active, you can always check the Viewer title bar to see whether currently loaded image contains a Z channel.) Combining Images With Different Channels In Shake, you can combine images that use different channels. For example, you can composite a 2-channel image over a 4-channel image. Shake is optimized to work on a per-channel basis-a 1-channel image usually calculates about three times faster than a 3-channel image. For this reason, if you read in masks from a different package, you are encouraged to make them 1-channel images to reduce disk space usage and processing time. 414 Chapter 15 Image Processing Basics