Spatial Filters Command
The Spatial Filter command applies a filter to an Image Set or a single image. This dialog organizes a large number of filters into a tree format based on their category. For example, all of the smoothing filters are grouped together under one heading and all the Sharpening filters are organized under a different heading. Selecting any filter loads all of its controls.
This command opens from the Process pull-down menu.
Filters are selected from the tree control on the left side of the dialog. The tree organizes filters into categories based on what they do. For example, the Smoothing node lists the group of filters whose primary effect is to smooth the image.
Click on the node containing the type of filter you want. Then click the desired filter to load its preferences.
Change the filter parameters if necessary.
To process the image using the selected filter, click [Process]. If you just want to update the filter's preferences that you have changed, click [Apply].
If you do not like the result, click Undo or use one of the standard Undo methods.
The table below describes each of the filters available in the Spatial Filters dialog.
Filter Descriptions
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Unsharp Mask |
Applies an unsharp mask sharpening filter. The parameters specify the blurring profile which is subtracted from the image. |
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Highpass |
Applies a "high pass" sharpening filter. The Strength parameter controls the effect. A setting of 0 performs almost no sharpening. |
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Rectangle |
Applies a rectangular smoothing kernel to the image. |
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Elliptical |
Applies an elliptical smoothing kernel to the image. |
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Gaussian |
Applies a Gaussian smoothing kernel to the image. |
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Block Average |
Combines adjacent pixels by averaging their values in blocks of a specified size. Each block of pixels becomes 1 pixel in the output image. |
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Minimum |
Replaces pixels with the minimum value of all pixels inside the filter kernel at each point. |
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Median |
Applies a Median filter to the image. This rejects outlying pixel values, no matter how extreme, and tends to preserve edges relatively well, but images can become "blocky" from using too large a kernel. This filter is accessible both from the Smoothing group and the Rank Filters group. |
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De-speckle |
Removes isolated speckles, or outlying pixel values. This is usually applied to RGB images to remove color channel noise. |
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Clip Low |
Replaces all pixels below a threshold value with a new value. |
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Clip High |
Replaces all pixels above a threshold value with a new value. |
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Rotational Gradient |
Applies a filter that mainly enhances structure that winds outward from points like the spokes of a bicycle wheel. |
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DDP |
Applies "Digital Development Processing", which is primarily an exponential stretch above a threshold value. |