Custom Filter Kernel
The Custom Filter Kernel command convolves a user-specified filter kernel. The filter kernel contains numeric weights to be applied to values in the neighborhood of each target pixel. The filter kernel is defined by its width, height, and kernel values entered into a grid. The kernel values are actually weights applied to pixels in the neighborhood of each target pixel of the image. The kernel may be any size you specify and a given kernel may also be normalized to a "volume" of 1.0 without typing in normalized weights.
The Custom Filter Kernel command opens
from the Image Window > Process
> Filters menu and 
button
on the Main Toolbar. The "immediate"
form, shown first, opens when an image or image set is displayed in
the top-most window. The general form can be used to select source
images from folders, windows, or by matching templates.
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Custom Filter Properties |
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Profile [|>] |
Selects the parameter profile for this command and allows you to save or work with existing presets. |
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[Select] |
Opens the Select Source Images dialog to choose images from an image window, folder, files, pattern, or a file list. |
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Custom Filter Kernel |
This group specified the properties of the kernel. Enter the filter width, height, and weights. |
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Width Sets the number of columns in the filter grid. |
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Height Sets the number of rows in the filter grid. |
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(Weights) Specify the weight for each element of the filter kernel. After entering weights, you can normalize the filter to unit weight by clicking the [Normalize] button. |
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[Normalize] |
Click this button to normalize the filter weights so the sum of weights is 1.0. |
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Source Region |
Specifies the rectangular region to be processed. The options are as follows: Entire image The entire image is processed. Image Cursor The region to be processed is selected using the Image Cursor. Rectangle The region specified by Min and Max limits for Column and Row coordinates is processed. Column and Row, Min and Max When Rectangle is selected, these values specify the column and row limits to be processed. |
The [Normalize] button changes the kernel values in the weight grid. When you click this button, all kernel values are summed to produce a normalization constant which is then divided into all kernel entries. The result is a kernel for which all weights sum to 1.0. Use normalization when the filter should preserve the signal level. A filter like the embossing filter example show here does not use normalization. In fact, the sum of kernel weights for this filter is 0.0.