Filter Nodes

The Filter nodes modify imagery (as opposed to combining it with other imagery like the Composite nodes). They take two inputs, the primary input and an optional control image input, as explained below in "Using Control Images with Filter Nodes ."

Note:
The Convolve node takes a second, optional input for use as a graphical kernel in the convolution, and a third, optional input for use as a control image.

The Filter nodes include color adjustment and area operation nodes; therefore they are discussed in two groups:

About the Color Filters
Color Correct Node
Brightness Node
Contrast Node
Gamma Node
Hue Adjust Node
Inverse Node
Monochrome Node
About the Area Filters
Blur Node
Convolve Node
Degrain Node
Edge Node
Erode/Dilate Node
Grain Node
Noise Node
Rank Node
Sharpen Node
Unsharp Mask Node

Using Control Images with Filter Nodes

The filter nodes accept an optional input image that is used to control which pixels of the primary input image will be processed in the filter operation.

Two control image parameters in the node panel enable you to specify which channel of the control image to use and how to use the channel data: the Control Action menu and the Control Channel menu.

Control Action Menu

The Control Action menu lets you specify how the information in the selected control channel will be used. The two methods are On/Off and Mix, and in both cases the value of each pixel in the control channel governs how the corresponding pixel in the primary input image will be used. (The "corresponding pixel" refers to the pixel with the same x,y image coordinates.)

On / Off Method

The On/Off method specifies whether a pixel will be operated on by the filter:

  • For any control channel pixel with a value of 0, the corresponding pixel of the primary image will not be filtered; that is, the original value of the pixel will be output unchanged.
  • For any control channel pixel with a nonzero value, the corresponding pixel in the primary image will be filtered by the node, just as it would if there was no control image input.

Mix Method

The Mix method uses the value of each control channel pixel to determine whether the corresponding pixel in the primary input will be filtered, and the extent to which it will be affected by the node operation.

As with the On/Off method, a control channel pixel with a value of 0 will turn off filtering, and a pixel with a value of 1 will turn filtering on. However, pixels with values in between 0 and 1 will be filtered, and the output will be a mixture of the filtered and unfiltered value of the primary input pixel, with the ratio being determined by the floating point value of the control channel pixel.

For example, a control channel pixel with a float value of 0.32 will turn on the filter 32 percent, so that the corresponding output pixel will be a mixture of 0.32 of the filtered input pixel value and 0.68 of the original input pixel value.

Control Channel Menu

This menu enables you to specify which channel in the control image will be used to govern the control action, when the control image has more than one channel.




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