Channel Processing Tools

Alpha Tools			Composition Tools
Chapter 11, 2D Compositing

Topics on this Page:

Channel Extract Tool

You can modify the individual color channels of an image using channel processing tools. These tools are in the Channel folder.

There are five channel processing tools:

Tool:	Description:
Channel Extract	Remove the red, blue, green, or alpha channel from an image--see Channel Extract Tool.
Out of Range	Analyze the channels of an image based on a specified thresholds--see Out of Range Tool.
Channel Replace	Remap the channels in one image by those in another image--see Channel Replace Tool.
Channel Rewire	Copy component values of an image to component values of an output image--see Channel Rewire Tool.

Channel Extract Tool

The Channel Extract tool lets you to remove a channel from an image. You can remove the red, green, blue, or alpha channel.

To extract a channel from an image:

Drag the Extract tool from the Channel folder on Tools tab onto the dependency graph in the Schematic view.
Click the channel list button and select the channel you want to extract from the image.

Note: The Channel Extract tool has a masking input--see Pixel Masking.

Out of Range Tool

The Out of Range tool uses pseudo colors to display pixels above or below user specified threshold. It is also capable of outputting a mask of the out-of-range pixels or its inverse, so that corrective action can be taken by other tools downstream. The Out of Range tool is in the Channel folder in the Tools tab.

The Out of Range tool has the following parameters:

Channel -- Select the source image channel to analyze.
Minimum -- Set the minimum value threshold of the source image channel.
Maximum -- Set the maximum value threshold of the source image channel.
In Range RGB -- Select the source image channel to display as the "In Range" color or deselect to use arbitrary color.
In Range Alpha -- Select the source image alpha channel to display as the "In Range" alpha or deselect to use arbitrary alpha value.
Below Range -- Select color to display pixels below the specified threshold.
In Range -- Select color to display pixels within the specified threshold.
Above Range -- Select color to display pixels above the specified threshold.

Examples

The following examples show you how the Out of Range tool can be used.

Viewing out of range alpha in a player -- Set the display modifier as a range display tool. An alpha below range will show up as opaque blue, an alpha above range will show up as opaque red, and all others will have their original alpha value.
Generating a matte from out of range alpha -- Using the range display tool, take the matte from the output image. Out of range pixels will have alpha of 1.0, all others will have alpha of 0.0.

Channel Replace Tool

The Channel Replace tool lets you remap the red, green, blue, or alpha channel values in one image by those of another image.

To remap the channel values of one image to a different image:

Drag the Replace tool from the Channel folder in Tools tab to the dependency graph in the Schematic view and connect the images to the tool node (one image for input A and one image for input B).
In the Tool UI, click the channel you want to replace and select values; A or B for Red, Green and Blue or A, B, or None for the Alpha channel.

Note: The Channel Replace tool has a masking input and its attributes are also animatable--see Pixel Masking and Animation Concepts.

Channel Rewire Tool

The Channel Rewire tool lets you create an output image that is generated by copying component values of the input image to (possibly different) component values of the output image. For each component of the output image, a selection list is used to choose the component of the input image.

To rewire an image:

Drag the Rewire tool from the Channel folder in Tools tab to the dependency graph in the Schematic view.
Select the input component(s) from the selection list.

Note: When Alpha is selected a sixth choice, None, is available.

Note: The Channel Rewire tool has a masking input and its attributes are also animatable--see Pixel Masking and Animation Concepts.

Set Alpha Tool

The Set Alpha tool lets you create (or replace, or add to) an alpha channel for an image (image A) input based on a component from a second image (image B). The selected component from image B may also be blended with the alpha component from image A.

To set a new, or replace an existing, alpha channel in an image:

To view the results of this operation, set the Channels selection to RGBA in the Composition tab of the Tool UI, or in Player Display Options, select Tool Output in the Display field and Channels: RGB in the View field.
Drag the Set Alpha tool from the Tools tab onto the dependency graph in the Schematic view.
Connect the images to the node (image A and image B).
Select the component from image B that you want to add to the alpha component from image A.
Blend the components until you are satisfied with the result.

Note: The Set Alpha tool's Blend attribute is animatable--see Animation Concepts.