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

  Program:   Visualization Toolkit
  Module:    $RCSfile: vtkImageDifference.h,v $

  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 vtkImageDifference - Compares images for regression tests.
// .SECTION Description
// vtkImageDifference takes two rgb unsigned char images and compares them.
// It allows the images to be slightly different.  If AllowShift is on,
// then each pixel can be shifted by one pixel. Threshold is the allowable
// error for each pixel.
//
// This is not a symetric filter and the difference computed is not symetric
// when AllowShift is on. Specifically in that case a pixel in SetImage input
// will be compared to the matching pixel in the input as well as to the
// input's eight connected neighbors. BUT... the opposite is not true. So for
// example if a valid image (SetImage) has a single white pixel in it, it
// will not find a match in the input image if the input image is black
// (because none of the nine suspect pixels are white). In contrast, if there
// is a single white pixel in the input image and the valid image (SetImage)
// is all black it will match with no error because all it has to do is find
// black pixels and even though the input image has a white pixel, its
// neighbors are not white.

#ifndef __vtkImageDifference_h
#define __vtkImageDifference_h

#include "vtkThreadedImageAlgorithm.h"

class VTK_IMAGING_EXPORT vtkImageDifference : public vtkThreadedImageAlgorithm
{
public:
  static vtkImageDifference *New();
  vtkTypeRevisionMacro(vtkImageDifference,vtkThreadedImageAlgorithm);
  void PrintSelf(ostream& os, vtkIndent indent);

  // Description:
  // Specify the Image to compare the input to.
  void SetImage(vtkDataObject *image) {this->SetInput(1,image);}
  vtkImageData *GetImage();

  // Description:
  // Return the total error in comparing the two images.
  double GetError(void);
  void GetError(double *e) { *e = this->GetError(); };
  
  // Description:
  // Return the total thresholded error in comparing the two images.
  // The thresholded error is the error for a given pixel minus the
  // threshold and clamped at a minimum of zero. 
  double GetThresholdedError(void);
  void GetThresholdedError(double *e) { *e = this->GetThresholdedError(); };


  // Description:
  // Specify a threshold tolerance for pixel differences.
  vtkSetMacro(Threshold,int);
  vtkGetMacro(Threshold,int);

  // Description:
  // Specify whether the comparison will allow a shift of one
  // pixel between the images.  If set, then the minimum difference
  // between input images will be used to determine the difference.
  // Otherwise, the difference is computed directly between pixels
  // of identical row/column values.
  vtkSetMacro(AllowShift,int);
  vtkGetMacro(AllowShift,int);
  vtkBooleanMacro(AllowShift,int);

  // Description:
  // Specify whether the comparison will include comparison of
  // averaged 3x3 data between the images. For graphics renderings
  // you normally would leave this on. For imaging operations it
  // should be off.
  vtkSetMacro(Averaging,int);
  vtkGetMacro(Averaging,int);
  vtkBooleanMacro(Averaging,int);

protected:
  vtkImageDifference();
  ~vtkImageDifference() {};

  double ErrorPerThread[VTK_MAX_THREADS];
  double ThresholdedErrorPerThread[VTK_MAX_THREADS];
  int AllowShift;
  int Threshold;
  int Averaging;
  
  virtual int RequestInformation (vtkInformation *, 
                                  vtkInformationVector **,
                                  vtkInformationVector *); 
  virtual int RequestUpdateExtent(vtkInformation *, 
                                  vtkInformationVector **,
                                  vtkInformationVector *);
  
  virtual void ThreadedRequestData(vtkInformation *request, 
                                   vtkInformationVector **inputVector, 
                                   vtkInformationVector *outputVector,
                                   vtkImageData ***inData, 
                                   vtkImageData **outData,
                                   int extent[6], int threadId);
  
private:
  vtkImageDifference(const vtkImageDifference&);  // Not implemented.
  void operator=(const vtkImageDifference&);  // Not implemented.
};

#endif