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416 Chapter 15 Image Processing Basics
To return to viewing the RGB channels, do one of the following:
m
Position the pointer in the Viewer, then press C.
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Click the View Channel button, then choose the RGB channel option from the pop-up
menu.
To display the R, G, or B channels individually, do one of the following:
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Press R to display the Red channel.
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Press G to display the Green channel.
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Press B to display the Blue channel.
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Click the View Channel button, then choose a color channel from the pop-up menu.
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Right-click the View Channel button, then choose a color channel from the shortcut
menu.
Changing the Number of Image Channels
As stated above, certain operations automatically add or remove channels. For
example, the Emboss and Monochrome nodes change an RGB image to a BW image,
and a non-uniform Add node changes a BW image to an RGB image. You can also
explicitly change the number of channels in an image with specific nodes.
The following nodes also potentially modify image channels:
Node Effect Operation
Color–Add Adds R, G, B, A, or Z. A value raised above 0 creates the specified channel.
Color–
Brightness
Removes RGB. A brightness value set to 0 removes the RGB channels.
Layer–Copy Adds R, G, B, A, or Z. Copies a channel from the second input to the example.
If you copy Z, the second image must have the Z channel.
Filter–Emboss Turns an RGB image to a
BW image.
This, of course, radically alters your image.
Color–
Monochrome
Turns an RGB image to a
BW image.
Uses a luminance balance, but you can adjust this to
push specific channels.
Color–Mult Removes R, G, B, A, or Z. Setting the R, G, B, A, or Z to 0 removes the specified
channels.
Color–Reorder Adds or removes
R, G, B, A, or Z.
By using n or 0, you remove the specified channel:
• rgbn or rgb0 removes the alpha channel.
• rgbal adds the luminance into the Z channel, thereby
creating a Z channel.
• rrra creates a 2-channel image, assuming the “a”
channel is not black.
• 000a or nnna turns the image into a 1-channel alpha
image.