VTK-5.0.0/Graphics/vtkLinkEdgels.cxx

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

  Program:   Visualization Toolkit
  Module:    $RCSfile: vtkLinkEdgels.cxx,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.

=========================================================================*/
#include "vtkLinkEdgels.h"

#include "vtkCellArray.h"
#include "vtkDoubleArray.h"
#include "vtkImageData.h"
#include "vtkInformation.h"
#include "vtkInformationVector.h"
#include "vtkMath.h"
#include "vtkObjectFactory.h"
#include "vtkPointData.h"
#include "vtkPolyData.h"

vtkCxxRevisionMacro(vtkLinkEdgels, "$Revision: 1.39 $");
vtkStandardNewMacro(vtkLinkEdgels);

// Construct instance of vtkLinkEdgels with GradientThreshold set to 
// 0.1, PhiThreshold set to 90 degrees and LinkThreshold set to 90 degrees.
vtkLinkEdgels::vtkLinkEdgels()
{
  this->GradientThreshold = 0.1;
  this->PhiThreshold = 90;
  this->LinkThreshold = 90;
}

int vtkLinkEdgels::RequestData(
  vtkInformation *vtkNotUsed(request),
  vtkInformationVector **inputVector,
  vtkInformationVector *outputVector)
{
  // get the info objects
  vtkInformation *inInfo = inputVector[0]->GetInformationObject(0);
  vtkInformation *outInfo = outputVector->GetInformationObject(0);

  // get the input and ouptut
  vtkImageData *input = vtkImageData::SafeDownCast(
    inInfo->Get(vtkDataObject::DATA_OBJECT()));
  vtkPolyData *output = vtkPolyData::SafeDownCast(
    outInfo->Get(vtkDataObject::DATA_OBJECT()));

  vtkPointData *pd;
  vtkPoints *newPts;
  vtkCellArray *newLines;
  vtkDoubleArray *inScalars;
  vtkDoubleArray *outScalars;
  vtkDoubleArray *outVectors;
  int *dimensions;
  double *CurrMap, *inDataPtr;
  vtkDataArray *inVectors;
  int ptId;
  
  vtkDebugMacro(<< "Extracting structured points geometry");

  pd = input->GetPointData();
  dimensions = input->GetDimensions();
  inScalars = vtkDoubleArray::SafeDownCast(pd->GetScalars());
  inVectors = pd->GetVectors();
  if ((input->GetNumberOfPoints()) < 2 || inScalars == NULL)
    {
    vtkErrorMacro(<<"No data to transform (or wrong data type)!");
    return 1;
    }

  // set up the input
  inDataPtr = inScalars->GetPointer(0);

  // Finally do edge following to extract the edge data from the Thin image
  newPts = vtkPoints::New();
  newLines = vtkCellArray::New();
  outScalars = vtkDoubleArray::New();
  outVectors = vtkDoubleArray::New();
  outVectors->SetNumberOfComponents(3);

  vtkDebugMacro("doing edge linking\n");
  //
  // Traverse all points, for each point find Gradient in the Image map.
  //
  for (ptId=0; ptId < dimensions[2]; ptId++)
    {
    CurrMap = inDataPtr + dimensions[0]*dimensions[1]*ptId;
    
    this->LinkEdgels(dimensions[0],dimensions[1],CurrMap, inVectors,
                     newLines,newPts,outScalars,outVectors,ptId);
    }
  
  output->SetPoints(newPts);
  output->SetLines(newLines);

  // Update ourselves
//  outScalars->ComputeRange();
  output->GetPointData()->SetScalars(outScalars);
  output->GetPointData()->SetVectors(outVectors);
  
  newPts->Delete();
  newLines->Delete();
  outScalars->Delete();
  outVectors->Delete();

  return 1;
}

// This method links the edges for one image. 
void vtkLinkEdgels::LinkEdgels(int xdim, int ydim, double *image, 
                               vtkDataArray *inVectors,
                               vtkCellArray *newLines, 
                               vtkPoints *newPts,
                               vtkDoubleArray *outScalars, 
                               vtkDoubleArray *outVectors,
                               int z)
{
  int **forward;
  int **backward;
  int x,y,ypos,zpos;
  int currX, currY, i;
  int newX, newY;
  double vec[3], vec1[3], vec2[3];
  double linkThresh, phiThresh;
  // these direction vectors are rotated 90 degrees
  // to convert gradient direction into edgel direction
  static double directions[8][2] = {
    {0,1},  {-0.707, 0.707},
    {-1,0}, {-0.707, -0.707},
    {0,-1}, {0.707, -0.707},
    {1,0},  {0.707, 0.707}}; 
  static int xoffset[8] = {1,1,0,-1,-1,-1,0,1};
  static int yoffset[8] = {0,1,1,1,0,-1,-1,-1};
  int length, start;
  int bestDirection = 0;
  double error, bestError;

  forward  = new int *[ydim];
  backward = new int *[ydim];
  for (i = 0; i < ydim; i++)
    {
    forward[i]  = new int [xdim];
    backward[i] = new int [xdim];
    memset(forward[i],0,xdim*sizeof(int));
    memset(backward[i],0,xdim*sizeof(int));
    }

  zpos = z*xdim*ydim;
  linkThresh = cos(this->LinkThreshold*3.1415926/180.0);
  phiThresh = cos(this->PhiThreshold*3.1415926/180.0);

  // first find all forward & backwards links
  for (y = 0; y < ydim; y++)
    {
    ypos = y*xdim;
    for (x = 0; x < xdim; x++)
      {
      // find forward and backward neighbor for this pixel
      // if its value is less than threshold then ignore it
      if (image[x+ypos] < this->GradientThreshold)
        {
        forward[y][x] = -1;
        backward[y][x] = -1;
        }
      else
        {
        // try all neighbors as forward, first try four connected
        inVectors->GetTuple(x+ypos+zpos,vec1); 
        vtkMath::Normalize(vec1); 
        // first eliminate based on phi1 - alpha
        bestError = 0;
        for (i = 0; i < 8; i += 2)
          {
          // make sure it passes the linkThresh test
          if ((directions[i][0]*vec1[0]+directions[i][1]*vec1[1]) >= 
              linkThresh)
            {
            // make sure we dont go off the edge and are >= GradientThresh
            // and it hasn't already been set
            if ((x + xoffset[i] >= 0)&&(x + xoffset[i] < xdim)&&
                (y + yoffset[i] >= 0)&&(y + yoffset[i] < ydim)&&
                (!backward[y+yoffset[i]][x+xoffset[i]])&&
                (image[x + xoffset[i] + (y+yoffset[i])*xdim] >=
                 this->GradientThreshold)) 
              {
              // satisfied the first test, now check second
              inVectors->GetTuple(x + xoffset[i] + 
                                   (y + yoffset[i])*xdim + zpos,vec2); 
              vtkMath::Normalize(vec2); 
              if ((vec1[0]*vec2[0] + vec1[1]*vec2[1]) >= phiThresh)
                {
                // pased phi - phi test does the forward neighbor
                // pass the link test
                if ((directions[i][0]*vec2[0]+directions[i][1]*vec2[1]) >= 
                    linkThresh)
                  {
                  // check against the current best solution
                  error = (directions[i][0]*vec2[0]+directions[i][1]*vec2[1])
                    + (directions[i][0]*vec1[0]+directions[i][1]*vec1[1])
                    + (vec1[0]*vec2[0] + vec1[1]*vec2[1]);
                  if (error > bestError)
                    {
                    bestDirection = i;
                    bestError = error;
                    }
                  }
                }
              }
            }
          }
        if (bestError > 0)
          {
          forward[y][x] = (bestDirection+1);
          backward[y+yoffset[bestDirection]][x+xoffset[bestDirection]] 
            = ((bestDirection+4)%8)+1;
          }
        else
          {
          // check the eight connected neighbors now
          for (i = 1; i < 8; i += 2)
            {
            // make sure it passes the linkThresh test
            if ((directions[i][0]*vec1[0]+directions[i][1]*vec1[1]) >= 
                linkThresh)
              {
              // make sure we dont go off the edge and are >= GradientThresh
              // and it hasn't already been set
              if ((x + xoffset[i] >= 0)&&(x + xoffset[i] < xdim)&&
                  (y + yoffset[i] >= 0)&&(y + yoffset[i] < ydim)&&
                  (!backward[y+yoffset[i]][x+xoffset[i]])&&
                  (image[x + xoffset[i] + (y+yoffset[i])*xdim] >=
                   this->GradientThreshold)) 
                {
                // satisfied the first test, now check second
                inVectors->GetTuple(x + xoffset[i] + 
                                     (y + yoffset[i])*xdim + zpos,vec2); 
                vtkMath::Normalize(vec2); 
                if ((vec1[0]*vec2[0] + vec1[1]*vec2[1]) >= phiThresh)
                  {
                  // pased phi - phi test does the forward neighbor
                  // pass the link test
                  if ((directions[i][0]*vec2[0]+directions[i][1]*vec2[1]) >= 
                      linkThresh)
                    {
                    // check against the current best solution
                    error = (directions[i][0]*vec2[0]+directions[i][1]*vec2[1])
                      + (directions[i][0]*vec1[0]+directions[i][1]*vec1[1])
                      + (vec1[0]*vec2[0] + vec1[1]*vec2[1]);
                    if (error > bestError)
                      {
                      bestDirection = i;
                      bestError = error;
                      }
                    }
                  }
                }
              }
            }
          if (bestError > 0)
            {
            forward[y][x] = (bestDirection+1);
            backward[y+yoffset[bestDirection]][x+xoffset[bestDirection]] 
              = ((bestDirection+4)%8)+1;
            }
          }
        }
      }
    }
  

  // now construct the chains
  vec[2] = z;
  for (y = 0; y < ydim; y++)
    {
    ypos = y*xdim;
    for (x = 0; x < xdim; x++)
      {
      // do we have part of an edgel chain ?
      // isolated edgels do not qualify
      if (backward[y][x] > 0)
        {
        // trace back to the beginning
        currX = x;
        currY = y;
        do
          {
          newX = currX + xoffset[backward[currY][currX] - 1];
          currY += yoffset[backward[currY][currX] - 1];
          currX = newX;
          }
        while ((currX != x || currY != y) && backward[currY][currX]);

        // now trace to the end and build the digital curve
        length = 0;
        start = outScalars->GetNumberOfTuples();
        newX = currX;
        newY = currY;
        do
          {
          currX = newX;
          currY = newY;
          outScalars->InsertNextTuple(&(image[currX + currY*xdim]));
          inVectors->GetTuple(currX+currY*xdim+zpos,vec2); 
          vtkMath::Normalize(vec2); 
          outVectors->InsertNextTuple(vec2);
          vec[0] = currX;
          vec[1] = currY;
          newPts->InsertNextPoint(vec);
          length++;

          // if there is a next pixel select it
          if (forward[currY][currX])
            {
            newX = currX + xoffset[forward[currY][currX] - 1];
            newY = currY + yoffset[forward[currY][currX] - 1];
            }
          // clear out this edgel now that were done with it
          backward[newY][newX] = 0;
          forward[currY][currX] = 0;
          }
        while ((currX != newX || currY != newY));
        
        // build up the cell
        newLines->InsertNextCell(length);
        for (i = 0; i < length; i++)
          {
          newLines->InsertCellPoint(start);
          start++;
          }
        }
      }
    }

  // free up the memory
  for (i = 0; i < ydim; i++)
    {
    delete [] forward[i];
    delete [] backward[i];
    }
  delete [] forward;
  delete [] backward;
}

int vtkLinkEdgels::FillInputPortInformation(int, vtkInformation *info)
{
  info->Set(vtkAlgorithm::INPUT_REQUIRED_DATA_TYPE(), "vtkImageData");
  return 1;
}

void vtkLinkEdgels::PrintSelf(ostream& os, vtkIndent indent)
{
  this->Superclass::PrintSelf(os,indent);

  os << indent << "GradientThreshold:" << this->GradientThreshold << "\n";
  os << indent << "LinkThreshold:" << this->LinkThreshold << "\n";
  os << indent << "PhiThreshold:" << this->PhiThreshold << "\n";
}