/*=========================================================================

  Program:   Visualization Toolkit
  Module:    vtkSubPixelPositionEdgels.h
  Language:  C++
  Date:      $Date$
  Version:   $Revision$

Copyright (c) 1993-2000 Ken Martin, Will Schroeder, Bill Lorensen 
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=========================================================================*/
// .NAME vtkSubPixelPositionEdgels - adjust edgel locations based on gradients.
// .SECTION Description
// vtkSubPixelPositionEdgels is a filter that takes a series of linked
// edgels (digital curves) and gradient maps as input. It then adjusts
// the edgel locations based on the gradient data. Specifically, the
// algorithm first determines the neighboring gradient magnitudes of
// an edgel using simple interpolation of its neighbors. It then fits
// the following three data points: negative gradient direction
// gradient magnitude, edgel gradient magnitude and positive gradient
// direction gradient magnitude to a quadratic function. It then
// solves this quadratic to find the maximum gradient location along
// the gradient orientation.  It then modifes the edgels location
// along the gradient orientation to the calculated maximum
// location. This algorithm does not adjust an edgel in the direction
// orthogonal to its gradient vector.

// .SECTION see also
// vtkImage vtkImageGradient vtkLinkEdgels

#ifndef __vtkSubPixelPositionEdgels_h
#define __vtkSubPixelPositionEdgels_h

#include "vtkPolyDataToPolyDataFilter.h"
#include "vtkStructuredPoints.h"

class VTK_EXPORT vtkSubPixelPositionEdgels : public vtkPolyDataToPolyDataFilter
{
public:
  static vtkSubPixelPositionEdgels *New();
  vtkTypeMacro(vtkSubPixelPositionEdgels,vtkPolyDataToPolyDataFilter);
  void PrintSelf(ostream& os, vtkIndent indent);

  // Description:
  // Override update method because execution can branch two ways 
  // (Input and GradMaps)
  void Update();

  // Description:
  // Set/Get the gradient data for doing the position adjustments.
  void SetGradMaps(vtkStructuredPoints *gm);
  vtkStructuredPoints *GetGradMaps();

  // Description:
  // These methods can make the positioning look for a target scalar value
  // instead of looking for a maximum.
  vtkSetMacro(TargetFlag, int);
  vtkGetMacro(TargetFlag, int);
  vtkBooleanMacro(TargetFlag, int);
  vtkSetMacro(TargetValue, float);
  vtkGetMacro(TargetValue, float);
  
protected:
  vtkSubPixelPositionEdgels();
  ~vtkSubPixelPositionEdgels();
  vtkSubPixelPositionEdgels(const vtkSubPixelPositionEdgels&) {};
  void operator=(const vtkSubPixelPositionEdgels&) {};

  // Usual data generation method
  void Execute();
  void Move(int xdim, int ydim, int zdim, int x, int y,
	    float *img, vtkVectors *inVecs, 
	    float *result, int z, float *aspect, float *resultNormal);
  // extension for target insted of maximum
  int TargetFlag;
  float TargetValue;
};

#endif


