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Moravec Interest Operator

The Moravec Interest Operator module identifies "interesting" points within the image using the Moravec Interest Operator detection technique. These points normally identify corners of objects as corners are good points to detect and track. The technique first calculates an edge map based on horizontal, vertical and both diagonal directions. From this edge map the maximum response of all these edges is recorded. Once all maximal edge responses have been calculated the point that is maximal with respect to its neighbors is identified as "interesting" and marked.

Interface

Instructions

1. Threshold - Select the threshold above which a point is considered interesting. Lower values allow less anchored points (less repeatability) to appear whereas higher values reduce the number of points identified but improve the repeatability (i.e. identifying the same point in successive images).

2. Window Size - Select the window size for the point detection. This will almost always be 3.

3. Corner Isolation - To eliminate points close to each other select an appropriate corner isolation number. This will ensure that points are at least X pixels from each other and prevents tight clustering of detected points.

4. Color - Select a color to display the detected corner points ontop of the current image.

5. Shape - Select the shape to use when displaying the detected corner points.

Example

SourceDetected Points (threshold=10)

Variables


MORAVEC_CORNERS - Each corner XY coordinate is saved into an array accessible by the MORAVEC_CORNERS variable. Using code similar to the following within a VBScript module will allow you to further process the corner points.

corners = GetArrayVariable("MORAVEC_CORNERS")

' write back to messages the first line ..
' note that line segments are defined by two endpoints
Write("First Coord: " & corners(0) & "," & corners(1) & vbCRLF)
Write("Second Coord: " & corners(2) & "," & corners(3))

See Also


Harris Corners
Sobel

For more information


Wikipedia - Corner detection


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