Rotational Gradient Filter

The Rotational Gradient Filter enhances image features having angular detail in an image. This is accomplished by a combination of shifting and rotating the image relative to itself in a specified direction about a specific point at which rotational detail originates. A dithering angle is used to rotationally offset enhanced details to make them more visible. The angle shift is very small but the much larger dithering angle helps clarify the details revealed by the angle shift. See an Example

The Rotational Gradient Filter 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.

Rotational Gradient Filter Properties

Profile [\|>]	Selects the parameter profile for this command and allows you to save or work with existing presets.
[Select]	Opens the Select Source Images dialog to choose images from an image window, folder, files, pattern, or a file list.
Direction	Specifies the azimuthal angle in which the local image gradient (slope) is measured.
X Center	Specifies the X (column) coordinate at the center of rotation and shift. A precise centroid value can be inserted by clicking the Get Cursor X,Y button.
Y Center	Specifies the Y (row) coordinate at the center of rotation and shift. A precise centroid value can be inserted by clicking the Get Cursor X,Y button.
Get Cursor X,Y	Inserts the center coordinates of the Image Cursor into the X Center and Y Center fields. If Use Centroid is checked, the centroid position is calculated near the center of the image cursor. This button is enabled only if the source image selection made using the [Select] button refers to a displayed image.
Use Centroid	Check this box to cause the Get Cursor X,Y button to return an accurate centroid position near the center of the Image Cursor.
Angle Shift	Species the angle offset used to calculate the angular gradient (intensity slope) value. This is often a small value of 1 degree or less.
Position Shift	Species the position offset used to calculate the spatial gradient (intensity slope) value. This is often a small value of 1 degree or less.

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