Filters (Spatial): Nonmaximum Suppression

This algorithm defines the edges of an image by calculating the nonmaximum suppression of an image at a user-defined scale. An edge is defined as the union of points for which the gradient magnitude assumes a maximum in the gradient direction.

Algorithms/FiltersSpatialNonmaximumSuppression.html For more information about the algorithm, refer to the MIPAV web site: {http://mipav.cit.nih.gov/documentation/HTML Algorithms/FiltersSpatialNonmaximumSuppression.html}.


Image types

The nonmaximum suppression image can be generated from 2D, 2.5D, and 3D black-and-white images. However, the option to output an edge image is only available for black-and-white 2D images.

Applying the Nonmaximum Suppression algorithm

To run this algorithm, complete the following steps:

  1. Open an image.
  2. Perform, as an option, any other image processing, such as improving the contrast, on the image.
  3. Select Algorithms > Filter (spatial) > Nonmaximum suppression. The Nonmaximum suppression dialog box (Figure 1) opens.
  4. Complete the information in the dialog box.
  5. Click OK. The algorithm begins to run.
A pop-up window appears with the status. The following message appears
"Calculating the Nonmaximum suppression."
When the algorithm finishes running, the pop-up window closes. Depending on whether you selected New image or Replace image, the results appear in a new window or replace the image to which the algorithm was applied.

 Note: For 2D images, if you selected Output edge image, a new window with an edge image appears.


Nonmaximum Suppression dialog box

Figure 1. Nonmaximum Suppression dialog box
X dimension
Indicates the scale of the Gaussian in the X direction (the default value is 1.0).
Y dimension
Indicates the scale of the Gaussian in the Y direction (the default value is 1.0).
Z dimension
Indicates the scale of the Gaussian in the Z direction (for 3D images only). The default value is 1.0.
Use image resolutions to normalize 'Z' scale
Normalizes the Z scale to compensate for the difference if the voxel resolution in distance per pixel is greater between slices than the voxel resolution in-plane (for 3D images only, the default value is enabled).
If enabled, then where Z = scale Z, XRs = image X resolution, and ZRs = image Z resolution).
Process each slice independently
Calculates nonmaximum suppression for each slice of the dataset independently (for 3D images only the default value is enabled).
New image
Shows the results of the algorithm in a new image window (default choice). If selected, an output edge image appears in a second new window.
Replace image
Replaces the current active image with the results of the algorithm.
Whole image
Applies the algorithm to the whole image (default choice).
VOI region(s)
Applies the algorithm inside VOIs. Outside VOIs, the pixel values are unchanged.
OK
Applies the algorithm according to the specifications in this dialog box.
Cancel
Disregards any changes that you made iin the dialog box and closes this dialog box.
Help
Displays online help for this dialog box.