Package boofcv.alg.segmentation.ms

Class SegmentMeanShiftSearch<T extends ImageBase<T>>

java.lang.Object
boofcv.alg.segmentation.ms.SegmentMeanShiftSearch<T>
All Implemented Interfaces:
Stoppable
Direct Known Subclasses:
SegmentMeanShiftSearchColor, SegmentMeanShiftSearchGray
public abstract class SegmentMeanShiftSearch<T extends ImageBase<T>> extends Object implements Stoppable

Performs the search step in mean-shift image segmentation [1]. The mode of a pixel is the point at which mean-shift converges when initialized at that pixel. Pixels which have the same mode belong to the same segment. The weight kernel G(|x-y|^2/h) has independent normalization factors h for spacial and color components. A precomputed Normal distribution is used for the weight kernel.

Output is provided in the form of an image where each pixel contains the index of a region the pixel belongs to. Three other lists provide color value of the region, number of pixels in the region and the location of the mean-shift peak for that region. This output is unlikely to be final processing step since it will over segment the image. Merging of similar modes and pruning of small regions is a common next step.

An approximation of running mean-shift on each pixel is performed if the 'fast' flag is set to true. The approximation is about 5x faster and works by saving the mean-shift trajectory [2]. All points along the trajectory are given the same mode. When performing mean-shift if a pixel is encountered which has already been assigned a mode the search stops. This approximation tends to produce more regions and reduces clustering quality in high texture regions.

NOTES:

  • Spacial distance is normalized by dividing the found Euclidean distance squared by the maximum possible Euclidean distance squared, thus ensuring it will be between 0 and 1.
  • Color distance is normalized by dividing it by the maximum allows Euclidean distance squared. If its distance is more than the maximum allowed value then G() will be zero.
  • Image edges are handled by truncating the spacial kernel. This truncation will create an asymmetric kernel, but there is really no good way to handle image edges.

CITATIONS:

  1. Comaniciu, Dorin, and Peter Meer. "Mean shift analysis and applications." Computer Vision, 1999. The Proceedings of the Seventh IEEE International Conference on. Vol. 2. IEEE, 1999.
  2. Christoudias, Christopher M., Bogdan Georgescu, and Peter Meer. "Synergism in low level vision." Pattern Recognition, 2002. Proceedings. 16th International Conference on. Vol. 4. IEEE, 2002.

  • Field Details

    • maxIterations

      protected int maxIterations

    • convergenceTol

      protected float convergenceTol

    • radiusX

      protected int radiusX

    • radiusY

      protected int radiusY

    • widthX

      protected int widthX

    • widthY

      protected int widthY

    • maxColorDistanceSq

      protected float maxColorDistanceSq

    • pixelToMode

      protected GrayS32 pixelToMode

    • quickMode

      protected GrayS32 quickMode

    • modeLocation

      protected DogArray<Point2D_I32> modeLocation

    • modeMemberCount

      protected DogArray_I32 modeMemberCount

    • modeColor

      protected DogArray<float[]> modeColor

    • spacialTable

      protected float[] spacialTable

    • weightTable

      protected float[] weightTable

    • image

      protected T extends ImageBase<T> image

    • modeX

      protected float modeX

    • modeY

      protected float modeY

    • stopRequested

      protected boolean stopRequested

  • Constructor Details

    • SegmentMeanShiftSearch

      protected SegmentMeanShiftSearch(int maxIterations, float convergenceTol, int radiusX, int radiusY, float maxColorDistance, boolean fast)
      Configures mean-shift segmentation
      Parameters:
      maxIterations - Maximum number of mean-shift iterations. Try 30
      convergenceTol - When the change is less than this amount stop. Try 0.005
      radiusX - Spacial kernel radius x-axis
      radiusY - Spacial kernel radius y-axis
      maxColorDistance - Maximum allowed Euclidean distance squared for the color component
      fast - Improve runtime by approximating running mean-shift on each pixel. Try true.

  • Method Details

    • process

      public abstract void process(T image)
      Performs mean-shift clustering on the input image
      Parameters:
      image - Input image

    • distanceSq

      public static float distanceSq(float[] a, float[] b)
      Returns the Euclidean distance squared between the two vectors

    • weight

      protected float weight(float distance)
      Returns the weight given the normalized distance. Instead of computing the kernel distance every time a lookup table with linear interpolation is used. The distance has a domain from 0 to 1, inclusive
      Parameters:
      distance - Normalized Euclidean distance squared. From 0 to 1.
      Returns:
      Weight.

    • getPixelToRegion

      public GrayS32 getPixelToRegion()
      From peak index to pixel index

    • getModeLocation

      public DogArray<Point2D_I32> getModeLocation()
      Location of each peak in the image

    • getRegionMemberCount

      public DogArray_I32 getRegionMemberCount()
      Number of pixels which each peak as a member

    • getModeColor

      public DogArray<float[]> getModeColor()

    • getImageType

      public abstract ImageType<T> getImageType()

    • requestStop

      public void requestStop()
      Specified by:
      requestStop in interface Stoppable

    • isStopRequested

      public boolean isStopRequested()
      Specified by:
      isStopRequested in interface Stoppable