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/*=========================================================================
Program: Visualization Toolkit
Module: vtkLinkEdgels.h
Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
All rights reserved.
See Copyright.txt or http://www.kitware.com/Copyright.htm for details.
This software is distributed WITHOUT ANY WARRANTY; without even
the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
PURPOSE. See the above copyright notice for more information.
=========================================================================*/
// .NAME vtkLinkEdgels - links edgels together to form digital curves.
// .SECTION Description
// vtkLinkEdgels links edgels into digital curves which are then stored
// as polylines. The algorithm works one pixel at a time only looking at
// its immediate neighbors. There is a GradientThreshold that can be set
// that eliminates any pixels with a smaller gradient value. This can
// be used as the lower threshold of a two value edgel thresholding.
//
// For the remaining edgels, links are first tried for the four
// connected neighbors. A successful neighbor will satisfy three
// tests. First both edgels must be above the gradient
// threshold. Second, the difference between the orientation between
// the two edgels (Alpha) and each edgels orientation (Phi) must be
// less than LinkThreshold. Third, the difference between the two
// edgels Phi values must be less than PhiThreshold.
// The most successful link is selected. The measure is simply the
// sum of the three angle differences (actually stored as the sum of
// the cosines). If none of the four connect neighbors succeeds, then
// the eight connect neighbors are examined using the same method.
//
// This filter requires gradient information so you will need to use
// a vtkImageGradient at some point prior to this filter. Typically
// a vtkNonMaximumSuppression filter is also used. vtkThresholdEdgels
// can be used to complete the two value edgel thresholding as used
// in a Canny edge detector. The vtkSubpixelPositionEdgels filter
// can also be used after this filter to adjust the edgel locations.
// .SECTION see also
// vtkImageData vtkImageGradient vtkImageNonMaximumSuppression
#ifndef __vtkLinkEdgels_h
#define __vtkLinkEdgels_h
#include "vtkPolyDataAlgorithm.h"
class vtkCellArray;
class vtkDataArray;
class vtkDoubleArray;
class vtkPoints;
class VTK_GRAPHICS_EXPORT vtkLinkEdgels : public vtkPolyDataAlgorithm
{
public:
vtkTypeMacro(vtkLinkEdgels,vtkPolyDataAlgorithm);
void PrintSelf(ostream& os, vtkIndent indent);
// Description:
// Construct instance of vtkLinkEdgels with GradientThreshold set to
// 0.1, PhiThreshold set to 90 degrees and LinkThreshold set to 90 degrees.
static vtkLinkEdgels *New();
// Description:
// Set/Get the threshold for Phi vs. Alpha link thresholding.
vtkSetMacro(LinkThreshold,double);
vtkGetMacro(LinkThreshold,double);
// Description:
// Set/get the threshold for Phi vs. Phi link thresholding.
vtkSetMacro(PhiThreshold,double);
vtkGetMacro(PhiThreshold,double);
// Description:
// Set/Get the threshold for image gradient thresholding.
vtkSetMacro(GradientThreshold,double);
vtkGetMacro(GradientThreshold,double);
protected:
vtkLinkEdgels();
~vtkLinkEdgels() {};
virtual int RequestData(vtkInformation *, vtkInformationVector **, vtkInformationVector *);
virtual int FillInputPortInformation(int port, vtkInformation *info);
void LinkEdgels(int xdim, int ydim,double *image, vtkDataArray *inVectors,
vtkCellArray *newLines, vtkPoints *newPts,
vtkDoubleArray *outScalars, vtkDoubleArray *outVectors,
int z);
double GradientThreshold;
double PhiThreshold;
double LinkThreshold;
private:
vtkLinkEdgels(const vtkLinkEdgels&); // Not implemented.
void operator=(const vtkLinkEdgels&); // Not implemented.
};
#endif
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