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

  Program:   Visualization Toolkit
  Module:    $RCSfile: vtkImageBlend.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 "vtkImageBlend.h"

#include "vtkImageData.h"
#include "vtkImageStencilData.h"
#include "vtkInformation.h"
#include "vtkInformationVector.h"
#include "vtkObjectFactory.h"
#include "vtkStreamingDemandDrivenPipeline.h"
#include "vtkPointData.h"

vtkCxxRevisionMacro(vtkImageBlend, "$Revision: 1.38.4.2 $");
vtkStandardNewMacro(vtkImageBlend);

//----------------------------------------------------------------------------
vtkImageBlend::vtkImageBlend()
{
  this->Opacity = 0;
  this->OpacityArrayLength = 0;
  this->BlendMode = VTK_IMAGE_BLEND_MODE_NORMAL;
  this->CompoundThreshold = 0.0;
  this->DataWasPassed = 0;

  // we have the image inputs and the optional stencil input
  this->SetNumberOfInputPorts(2);
}

//----------------------------------------------------------------------------
vtkImageBlend::~vtkImageBlend()
{
  if (this->Opacity)
    {
    delete [] this->Opacity;
    }
  this->OpacityArrayLength = 0;
}

//----------------------------------------------------------------------------
// The default vtkImageAlgorithm semantics are that SetInput() puts
// each input on a different port, we want all the image inputs to
// go on the first port.
void vtkImageBlend::SetInput(int idx, vtkDataObject *input)
{
  // Ask the superclass to connect the input.
  this->SetNthInputConnection(0, idx, (input ? input->GetProducerPort() : 0));
}

//----------------------------------------------------------------------------
vtkDataObject *vtkImageBlend::GetInput(int idx)
{
  if (this->GetNumberOfInputConnections(0) <= idx)
    {
    return 0;
    }
  return vtkImageData::SafeDownCast(
    this->GetExecutive()->GetInputData(0, idx));
}

//----------------------------------------------------------------------------
void vtkImageBlend::SetStencil(vtkImageStencilData *stencil)
{
  // if stencil is null, then set the input port to null
  this->SetNthInputConnection(1, 0, 
    (stencil ? stencil->GetProducerPort() : 0));
}


//----------------------------------------------------------------------------
vtkImageStencilData *vtkImageBlend::GetStencil()
{
  if (this->GetNumberOfInputConnections(1) < 1)
    {
    return 0;
    }
  return vtkImageStencilData::SafeDownCast(
    this->GetExecutive()->GetInputData(1, 0));
}

//----------------------------------------------------------------------------
void vtkImageBlend::SetOpacity(int idx, double opacity)
{
  int i;
  int newLength;
  double *newArray;

  if (opacity < 0.0)
    {
    opacity = 0.0;
    }
  if (opacity > 1.0)
    {
    opacity = 1.0;
    }

  if (idx >= this->OpacityArrayLength)
    {
    newLength = idx + 1; 
    newArray = new double[newLength];
    for (i = 0; i < this->OpacityArrayLength; i++)
      {
      newArray[i] = this->Opacity[i];
      }
    for (; i < newLength; i++)
      {
      newArray[i] = 1.0;
      }
    if (this->Opacity)
      {
      delete [] this->Opacity;
      }
    this->Opacity = newArray;
    this->OpacityArrayLength = newLength;
    }

  if (this->Opacity[idx] != opacity)
    {
    this->Opacity[idx] = opacity;
    this->Modified();
    }
}
    
//----------------------------------------------------------------------------
double vtkImageBlend::GetOpacity(int idx)
{
  if (idx >= this->OpacityArrayLength)
    {
    return 1.0;
    }
  return this->Opacity[idx];
}    

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

  // this is some scary stuff, propagating info upstream??? - Ken
  vtkImageStencilData *stencil = this->GetStencil();
  if (stencil)
    {
    stencil->SetSpacing(inInfo->Get(vtkDataObject::SPACING()));
    stencil->SetOrigin(inInfo->Get(vtkDataObject::ORIGIN()));
    }

  return 1;
}

//----------------------------------------------------------------------------
// This method computes the extent of the input region necessary to generate
// an output region.  Before this method is called "region" should have the
// extent of the output region.  After this method finishes, "region" should
// have the extent of the required input region.  The default method assumes
// the required input extent are the same as the output extent.
// Note: The splitting methods call this method with outRegion = inRegion.
void vtkImageBlend::InternalComputeInputUpdateExtent(int inExt[6],
                                                     int outExt[6],
                                                     int wholeExtent[6])
{
  memcpy(inExt,outExt,sizeof(int)*6);

  int i;

  // clip with the whole extent
  for (i = 0; i < 3; i++)
    {
    if (inExt[2*i] < wholeExtent[2*i])
      {
      inExt[2*i] = wholeExtent[2*i];
      }
    if (inExt[2*i+1] > wholeExtent[2*i+1])
      {
      inExt[2*i+1] = wholeExtent[2*i+1];
      }
    }
}

//----------------------------------------------------------------------------
int vtkImageBlend::RequestUpdateExtent(
  vtkInformation * vtkNotUsed(request),
  vtkInformationVector **inputVector,
  vtkInformationVector *outputVector)
{
  // get the info objects
  vtkInformation* outInfo = outputVector->GetInformationObject(0);
  
  // default input extent will be that of output extent
  int inExt[6];
  int *outExt = 
    outInfo->Get(vtkStreamingDemandDrivenPipeline::UPDATE_EXTENT());

  int whichInput;
  for (whichInput = 0; whichInput < this->GetNumberOfInputConnections(0); 
       whichInput++)
    {
    int *inWextent;
    vtkInformation *inInfo = inputVector[0]->GetInformationObject(whichInput);
    inWextent = inInfo->Get(vtkStreamingDemandDrivenPipeline::WHOLE_EXTENT());
    this->InternalComputeInputUpdateExtent(inExt, outExt, inWextent);
    inInfo->Set(vtkStreamingDemandDrivenPipeline::UPDATE_EXTENT(),inExt,6);
    }

  return 1;
}

int vtkImageBlend::RequestData(
  vtkInformation* request,
  vtkInformationVector** inputVector,
  vtkInformationVector* outputVector)
{
  // check to see if we have more than one input
  if (this->GetNumberOfInputConnections(0) == 1)
    {
    vtkDebugMacro("RequestData: single input, passing data");

    vtkInformation* info = outputVector->GetInformationObject(0);
    vtkImageData *outData = static_cast<vtkImageData *>(
      info->Get(vtkDataObject::DATA_OBJECT()));
    info = inputVector[0]->GetInformationObject(0);
    vtkImageData *inData = 
      static_cast<vtkImageData*>(info->Get(vtkDataObject::DATA_OBJECT()));
    
    outData->SetExtent(inData->GetExtent());
    outData->GetPointData()->PassData(inData->GetPointData());
    this->DataWasPassed = 1;
    }
  else // multiple inputs
    {
    vtkInformation* info = outputVector->GetInformationObject(0);
    vtkImageData *outData = static_cast<vtkImageData *>(
      info->Get(vtkDataObject::DATA_OBJECT()));
    if (this->DataWasPassed)
      {
      outData->GetPointData()->SetScalars(NULL);
      this->DataWasPassed = 0;
      }
    return this->Superclass::RequestData(request,inputVector,outputVector);
    }

  return 1;
}

//----------------------------------------------------------------------------
// helper function for the stencil
template <class T>
inline int vtkBlendGetNextExtent(vtkImageStencilData *stencil,
                                 int &r1, int &r2, int rmin, int rmax,
                                 int yIdx, int zIdx, 
                                 T *&outPtr, T *&inPtr, 
                                 int outScalars, int inScalars,
                                 int &iter)
{
  // trivial case if stencil is not set
  if (!stencil)
    {
    if (iter++ == 0)
      {
      r1 = rmin;
      r2 = rmax;
      return 1;
      }
    return 0;
    }

  // save r2
  int oldr2 = r2;
  if (iter == 0)
    { // if no 'last time', start just before rmin
    oldr2 = rmin - 1;
    }

  int rval = stencil->GetNextExtent(r1, r2, rmin, rmax, yIdx, zIdx, iter);
  int incr = r1 - oldr2 - 1;
  if (rval == 0)
    {
    incr = rmax - oldr2;
    }

  outPtr += incr*outScalars;
  inPtr += incr*inScalars;

  return rval;
}

//----------------------------------------------------------------------------
// This templated function executes the filter for any type of data.
template <class T>
void vtkImageBlendExecute(vtkImageBlend *self, int extent[6], 
                          vtkImageData *inData, T *inPtr,
                          vtkImageData *outData, T *outPtr,
                          double opacity, int id)
{
  int idxX, idxY, idxZ;
  int minX = 0;
  int maxX = 0;
  int iter;
  vtkIdType inIncX, inIncY, inIncZ;
  vtkIdType outIncX, outIncY, outIncZ;
  int inC, outC;
  double minA, maxA;
  double r, f;
  unsigned long count = 0;
  unsigned long target;

  vtkImageStencilData *stencil = self->GetStencil();

  if (inData->GetScalarType() == VTK_DOUBLE ||
      inData->GetScalarType() == VTK_FLOAT)
    {
    minA = 0.0;
    maxA = 1.0;
    }
  else
    {
    minA = inData->GetScalarTypeMin();
    maxA = inData->GetScalarTypeMax();
    }

  r = opacity;
  f = 1.0 - r;

  opacity = opacity/(maxA-minA);

  inC = inData->GetNumberOfScalarComponents();
  outC = outData->GetNumberOfScalarComponents();

  target = (unsigned long)((extent[3] - extent[2] + 1)*
                           (extent[5] - extent[4] + 1)/50.0);
  target++;
  
  // Get increments to march through data 
  inData->GetContinuousIncrements(extent, inIncX, inIncY, inIncZ);
  outData->GetContinuousIncrements(extent, outIncX, outIncY, outIncZ);

  // Loop through output pixels
  for (idxZ = extent[4]; idxZ <= extent[5]; idxZ++)
    {
    for (idxY = extent[2]; !self->AbortExecute && idxY <= extent[3]; idxY++)
      {
      if (!id) 
        {
        if (!(count%target))
          {
          self->UpdateProgress(count/(50.0*target));
          }
        count++;
        }

      iter = 0;
      if (outC >= 3 && inC >= 4)
        { // RGB(A) blended with RGBA
        while (vtkBlendGetNextExtent(stencil, minX, maxX, extent[0], extent[1],
                                     idxY, idxZ,
                                     outPtr, inPtr, outC, inC, iter))
          {
          for (idxX = minX; idxX <= maxX; idxX++)
            {
            r = opacity*(inPtr[3]-minA);
            f = 1.0-r;
            outPtr[0] = T(outPtr[0]*f + inPtr[0]*r);
            outPtr[1] = T(outPtr[1]*f + inPtr[1]*r);
            outPtr[2] = T(outPtr[2]*f + inPtr[2]*r);
            outPtr += outC; 
            inPtr += inC;
            }
          }
        }
      else if (outC >= 3 && inC == 3)
        { // RGB(A) blended with RGB
        while (vtkBlendGetNextExtent(stencil, minX, maxX, extent[0], extent[1],
                                     idxY, idxZ,
                                     outPtr, inPtr, outC, inC, iter))
          {
          for (idxX = minX; idxX <= maxX; idxX++)
            {
            outPtr[0] = T(outPtr[0]*f + inPtr[0]*r);
            outPtr[1] = T(outPtr[1]*f + inPtr[1]*r);
            outPtr[2] = T(outPtr[2]*f + inPtr[2]*r);
            outPtr += outC; 
            inPtr += inC;
            }
          }
        }
      else if (outC >= 3 && inC == 2)
        { // RGB(A) blended with luminance+alpha
        while (vtkBlendGetNextExtent(stencil, minX, maxX, extent[0], extent[1],
                                     idxY, idxZ,
                                     outPtr, inPtr, outC, inC, iter))
          {
          for (idxX = minX; idxX <= maxX; idxX++)
            {
            r = opacity*(inPtr[1]-minA);
            f = 1.0-r;
            outPtr[0] = T(outPtr[0]*f + (*inPtr)*r);
            outPtr[1] = T(outPtr[1]*f + (*inPtr)*r);
            outPtr[2] = T(outPtr[2]*f + (*inPtr)*r);
            outPtr += outC; 
            inPtr += 2;
            }
          }
        }
      else if (outC >= 3 && inC == 1)
        { // RGB(A) blended with luminance
        while (vtkBlendGetNextExtent(stencil, minX, maxX, extent[0], extent[1],
                                     idxY, idxZ,
                                     outPtr, inPtr, outC, inC, iter))
          {
          for (idxX = minX; idxX <= maxX; idxX++)
            {
            outPtr[0] = T(outPtr[0]*f + (*inPtr)*r);
            outPtr[1] = T(outPtr[1]*f + (*inPtr)*r);
            outPtr[2] = T(outPtr[2]*f + (*inPtr)*r);
            outPtr += outC; 
            inPtr++;
            }
          }
        }
      else if (inC == 2)
        { // luminance(+alpha) blended with luminance+alpha
        while (vtkBlendGetNextExtent(stencil, minX, maxX, extent[0], extent[1],
                                     idxY, idxZ,
                                     outPtr, inPtr, outC, inC, iter))
          {
          for (idxX = minX; idxX <= maxX; idxX++)
            {
            r = opacity*(inPtr[1]-minA);
            f = 1.0-r;
            *outPtr = T((*outPtr)*f + (*inPtr)*r);
            outPtr += outC; 
            inPtr += 2;
            }
          }
        }
      else
        { // luminance(+alpha) blended with luminance
        while (vtkBlendGetNextExtent(stencil, minX, maxX, extent[0], extent[1],
                                     idxY, idxZ,
                                     outPtr, inPtr, outC, inC, iter))
          {
          for (idxX = minX; idxX <= maxX; idxX++)
            {
            *outPtr = T((*outPtr)*f + (*inPtr)*r);
            outPtr += outC; 
            inPtr++;
            }
          }
        }
      outPtr += outIncY;
      inPtr += inIncY;
      }
    outPtr += outIncZ;
    inPtr += inIncZ;
    }
}

//----------------------------------------------------------------------------
// This templated function executes the filter specifically for char data
template <class T>
void vtkImageBlendExecuteChar(vtkImageBlend *self, int extent[6], 
                              vtkImageData *inData, T *inPtr,
                              vtkImageData *outData, T *outPtr,
                              double opacity, int id)
{
  int idxX, idxY, idxZ;
  int minX = 0;
  int maxX = 0;
  int iter;
  vtkIdType inIncX, inIncY, inIncZ;
  vtkIdType outIncX, outIncY, outIncZ;
  int inC, outC;
  unsigned short r, f, o;
  int v0, v1, v2;
  unsigned long count = 0;
  unsigned long target;

  vtkImageStencilData *stencil = self->GetStencil();

  // round opacity to a value in the range [0,256], because division
  // by 256 can be efficiently achieved by bit-shifting by 8 bits
  o = (unsigned short)(256*opacity + 0.5);
  r = o;
  f = 256 - o;

  inC = inData->GetNumberOfScalarComponents();
  outC = outData->GetNumberOfScalarComponents();

  target = (unsigned long)((extent[3] - extent[2] + 1)*
                           (extent[5] - extent[4] + 1)/50.0);
  target++;  

  // Get increments to march through data 
  inData->GetContinuousIncrements(extent, inIncX, inIncY, inIncZ);
  outData->GetContinuousIncrements(extent, outIncX, outIncY, outIncZ);

  // Loop through ouput pixels
  for (idxZ = extent[4]; idxZ <= extent[5]; idxZ++)
    {
    for (idxY = extent[2]; !self->AbortExecute && idxY <= extent[3]; idxY++)
      {
      if (!id) 
        {
        if (!(count%target))
          {
          self->UpdateProgress(count/(50.0*target));
          }
        count++;
        }
      
      iter = 0;
      if (outC >= 3 && inC >= 4)
        { // RGB(A) blended with RGBA
        while (vtkBlendGetNextExtent(stencil, minX, maxX, extent[0], extent[1],
                                     idxY, idxZ,
                                     outPtr, inPtr, outC, inC, iter))
          {
          for (idxX = minX; idxX <= maxX; idxX++)
            {
            // multiply to get a number in the range [0,65280]
            // where 65280 = 255*256 = range of inPtr[3] * range of o
            r = inPtr[3]*o;
            f = 65280 - r;
            v0 = outPtr[0]*f + inPtr[0]*r;
            v1 = outPtr[1]*f + inPtr[1]*r;
            v2 = outPtr[2]*f + inPtr[2]*r;
            // do some math tricks to achieve division by 65280:
            // this is not an approximation, it gives exactly the
            // same result as an integer division by 65280
            outPtr[0] = (v0 + (v0 >> 8) + (v0 >> 16) + 1) >> 16;
            outPtr[1] = (v1 + (v1 >> 8) + (v1 >> 16) + 1) >> 16;
            outPtr[2] = (v2 + (v2 >> 8) + (v2 >> 16) + 1) >> 16;
            inPtr += inC;
            outPtr += outC; 
            }
          }
        }
      else if (outC >= 3 && inC == 3)
        { // RGB(A) blended with RGB
        while (vtkBlendGetNextExtent(stencil, minX, maxX, extent[0], extent[1],
                                     idxY, idxZ,
                                     outPtr, inPtr, outC, inC, iter))
          {
          for (idxX = minX; idxX <= maxX; idxX++)
            {
            // the bit-shift achieves a division by 256
            outPtr[0] = (outPtr[0]*f + inPtr[0]*r) >> 8;
            outPtr[1] = (outPtr[1]*f + inPtr[1]*r) >> 8;
            outPtr[2] = (outPtr[2]*f + inPtr[2]*r) >> 8;
            inPtr += 3;
            outPtr += outC; 
            }
          }
        }
      else if (outC >= 3 && inC == 2)
        { // RGB(A) blended with luminance+alpha
        while (vtkBlendGetNextExtent(stencil, minX, maxX, extent[0], extent[1],
                                     idxY, idxZ,
                                     outPtr, inPtr, outC, inC, iter))
          {
          for (idxX = minX; idxX <= maxX; idxX++)
            {
            // multiply to get a number in the range [0,65280]
            // where 65280 = 255*256 = range of inPtr[1] * range of o
            r = inPtr[1]*o;
            f = 65280 - r;
            v0 = outPtr[0]*f + inPtr[0]*r;
            v1 = outPtr[1]*f + inPtr[0]*r;
            v2 = outPtr[2]*f + inPtr[0]*r;
            // do some math tricks to achieve division by 65280:
            // this is not an approximation, it gives exactly the
            // same result as an integer division by 65280
            outPtr[0] = (v0 + (v0 >> 8) + (v0 >> 16) + 1) >> 16;
            outPtr[1] = (v1 + (v1 >> 8) + (v1 >> 16) + 1) >> 16;
            outPtr[2] = (v2 + (v2 >> 8) + (v2 >> 16) + 1) >> 16;
            inPtr += 2;
            outPtr += outC; 
            }
          }
        }
      else if (outC >= 3 && inC == 1)
        { // RGB(A) blended with luminance
        while (vtkBlendGetNextExtent(stencil, minX, maxX, extent[0], extent[1],
                                     idxY, idxZ,
                                     outPtr, inPtr, outC, inC, iter))
          {
          for (idxX = minX; idxX <= maxX; idxX++)
            {
            // the bit-shift achieves a division by 256
            outPtr[0] = (outPtr[0]*f + inPtr[0]*r) >> 8;
            outPtr[1] = (outPtr[1]*f + inPtr[0]*r) >> 8;
            outPtr[2] = (outPtr[2]*f + inPtr[0]*r) >> 8;
            inPtr++;
            outPtr += outC; 
            }
          }
        }
      else if (inC == 2)
        { // luminance(+alpha) blended with luminance+alpha
        while (vtkBlendGetNextExtent(stencil, minX, maxX, extent[0], extent[1],
                                     idxY, idxZ,
                                     outPtr, inPtr, outC, inC, iter))
          {
          for (idxX = minX; idxX <= maxX; idxX++)
            {
            // multiply to get a number in the range [0,65280]
            // where 65280 = 255*256 = range of inPtr[1] * range of o
            r = inPtr[1]*o;
            f = 65280 - r;
            v0 = outPtr[0]*f + inPtr[0]*r;
            // do some math tricks to achieve division by 65280:
            // this is not an approximation, it gives exactly the
            // same result as an integer division by 65280
            outPtr[0] = (v0 + (v0 >> 8) + (v0 >> 16) + 1) >> 16;
            inPtr += 2;
            outPtr += outC; 
            }
          }
        }
      else
        { // luminance(+alpha) blended with luminance
        while (vtkBlendGetNextExtent(stencil, minX, maxX, extent[0], extent[1],
                                     idxY, idxZ,
                                     outPtr, inPtr, outC, inC, iter))
          {
          for (idxX = minX; idxX <= maxX; idxX++)
            {
            // the bit-shift achieves a division by 256
            outPtr[0] = (outPtr[0]*f + inPtr[0]*r) >> 8;
            inPtr++;
            outPtr += outC; 
            }
          }
        }
      outPtr += outIncY;
      inPtr += inIncY;
      }
    outPtr += outIncZ;
    inPtr += inIncZ;
    }
}


//----------------------------------------------------------------------------
// This function simply does a copy (for the first input)
//----------------------------------------------------------------------------
void vtkImageBlendCopyData(vtkImageData *inData, vtkImageData *outData,
                           int *ext)
{
  int idxY, idxZ, maxY, maxZ;
  vtkIdType inIncX, inIncY, inIncZ;
  int rowLength;
  unsigned char *inPtr, *inPtr1, *outPtr;
 
  inPtr = (unsigned char *) inData->GetScalarPointerForExtent(ext);
  outPtr = (unsigned char *) outData->GetScalarPointerForExtent(ext);
 
  // Get increments to march through inData
  inData->GetIncrements(inIncX, inIncY, inIncZ);
 
  // find the region to loop over
  rowLength = (ext[1] - ext[0]+1)*inIncX*inData->GetScalarSize();
  maxY = ext[3] - ext[2];
  maxZ = ext[5] - ext[4];

  inIncY *= inData->GetScalarSize();
  inIncZ *= inData->GetScalarSize();

  // Loop through outData pixels
  for (idxZ = 0; idxZ <= maxZ; idxZ++)
    {
    inPtr1 = inPtr + idxZ*inIncZ;
    for (idxY = 0; idxY <= maxY; idxY++)
      {
      memcpy(outPtr,inPtr1,rowLength);
      inPtr1 += inIncY;
      outPtr += rowLength;
      }
    }
}


//----------------------------------------------------------------------------
// This templated function executes the filter for any type of data.
template <class T>
void vtkImageBlendCompoundExecute(vtkImageBlend *self,
                                  int extent[6], 
                                  vtkImageData *inData, 
                                  T *inPtr,
                                  vtkImageData *tmpData, 
                                  double opacity,
                                  double threshold)
{
  unsigned long count = 0;
  unsigned long target;

  target = (unsigned long)((extent[3] - extent[2] + 1)*
                           (extent[5] - extent[4] + 1)/50.0);
  target++;
  
  // Get increments to march through data 

  vtkIdType inIncX, inIncY, inIncZ;
  int inC;

  inData->GetContinuousIncrements(extent, inIncX, inIncY, inIncZ);
  inC = inData->GetNumberOfScalarComponents();

  vtkIdType tmpIncX, tmpIncY, tmpIncZ;
  int tmpC;

  tmpData->GetContinuousIncrements(extent, tmpIncX, tmpIncY, tmpIncZ);
  tmpC = tmpData->GetNumberOfScalarComponents();

  double* tmpPtr = (double *)tmpData->GetScalarPointerForExtent(extent);  

  // Opacity
  double minA, maxA;
  double r;

  if (inData->GetScalarType() == VTK_DOUBLE ||
      inData->GetScalarType() == VTK_FLOAT)
    {
    minA = 0.0;
    maxA = 1.0;
    }
  else
    {
    minA = (double)inData->GetScalarTypeMin();
    maxA = (double)inData->GetScalarTypeMax();
    }

  r = opacity;
  opacity = opacity/(maxA-minA);

  if ((inC == 3 || inC == 1) && r <= threshold)
    {
    return;
    }

  // Loop through output pixels

  for (int idxZ = extent[4]; idxZ <= extent[5]; idxZ++)
    {
    for (int idxY = extent[2]; !self->AbortExecute && idxY<=extent[3]; idxY++)
      {
      if (!(count%target))
        {
        self->UpdateProgress(count/(50.0*target));
        }
      count++;
      
      if (tmpC >= 3)
        {

        // RGB(A) blended with RGBA
        if (inC >= 4)
          { 
          for (int idxX = extent[0]; idxX <= extent[1]; idxX++)
            {
            r = opacity * ((double)inPtr[3] - minA);
            if (r > threshold) 
              {
              tmpPtr[0] += (double)inPtr[0] * r;
              tmpPtr[1] += (double)inPtr[1] * r;
              tmpPtr[2] += (double)inPtr[2] * r;
              tmpPtr[3] += r;
              }
            tmpPtr += 4; 
            inPtr += inC;
            }
          }

        // RGB(A) blended with RGB
        else if (inC == 3)
          { 
          for (int idxX = extent[0]; idxX <= extent[1]; idxX++)
            {
            tmpPtr[0] += (double)inPtr[0] * r;
            tmpPtr[1] += (double)inPtr[1] * r;
            tmpPtr[2] += (double)inPtr[2] * r;
            tmpPtr[3] += r;
            tmpPtr += 4; 
            inPtr += inC;
            }
          }

        // RGB(A) blended with luminance+alpha
        else if (inC == 2)
          { 
          for (int idxX = extent[0]; idxX <= extent[1]; idxX++)
            {
            r = opacity * ((double)inPtr[1] - minA);
            if (r > threshold) 
              {
              tmpPtr[0] += (double)(*inPtr) * r;
              tmpPtr[1] += (double)(*inPtr) * r;
              tmpPtr[2] += (double)(*inPtr) * r;
              tmpPtr[3] += r;
              }
            tmpPtr += 4; 
            inPtr += 2;
            }
          }

        // RGB(A) blended with luminance
        else if (inC == 1)
          { 
          for (int idxX = extent[0]; idxX <= extent[1]; idxX++)
            {
            tmpPtr[0] += (double)(*inPtr) * r;
            tmpPtr[1] += (double)(*inPtr) * r;
            tmpPtr[2] += (double)(*inPtr) * r;
            tmpPtr[3] += r;
            tmpPtr += 4; 
            inPtr++;
            }
          }
        }

      // luminance(+alpha) blended with luminance+alpha
      else if (inC == 2)
        { 
        for (int idxX = extent[0]; idxX <= extent[1]; idxX++)
          {
          r = opacity * ((double)inPtr[1] - minA);
          if (r > threshold) 
            {
            tmpPtr[0] = (double)(*inPtr) * r;
            tmpPtr[1] += r;
            }
          tmpPtr += 2; 
          inPtr += 2;
          }
        }

      // luminance(+alpha) blended with luminance
      else
        { 
        for (int idxX = extent[0]; idxX <= extent[1]; idxX++)
          {
          tmpPtr[0] = (double)(*inPtr) * r;
          tmpPtr[1] += r;
          tmpPtr += 2; 
          inPtr++;
          }
        }

      tmpPtr += tmpIncY;
      inPtr += inIncY;
      }
    tmpPtr += tmpIncZ;
    inPtr += inIncZ;
    }
}


//----------------------------------------------------------------------------
// This templated function executes the filter for any type of data.
template <class T>
void vtkImageBlendCompoundTransferExecute(vtkImageBlend *self,
                                          int extent[6], 
                                          vtkImageData *outData, 
                                          T *outPtr,
                                          vtkImageData *tmpData)
{
  // Get increments to march through data 

  vtkIdType outIncX, outIncY, outIncZ;
  int outC;

  outData->GetContinuousIncrements(extent, outIncX, outIncY, outIncZ);
  outC = outData->GetNumberOfScalarComponents();

  vtkIdType tmpIncX, tmpIncY, tmpIncZ;
  int tmpC;

  tmpData->GetContinuousIncrements(extent, tmpIncX, tmpIncY, tmpIncZ);
  tmpC = tmpData->GetNumberOfScalarComponents();

  double* tmpPtr = (double *)tmpData->GetScalarPointerForExtent(extent);  

  // Loop through output pixels

  for (int idxZ = extent[4]; idxZ <= extent[5]; idxZ++)
    {
    for (int idxY = extent[2]; !self->AbortExecute && idxY<=extent[3]; idxY++)
      {
      if (tmpC >= 3)
        {
        for (int idxX = extent[0]; idxX <= extent[1]; idxX++)
          {
          double factor = 0.0;
          if (tmpPtr[3] != 0)
            {
            factor = 1.0/tmpPtr[3];
            }
          outPtr[0] = T(tmpPtr[0]*factor);
          outPtr[1] = T(tmpPtr[1]*factor);
          outPtr[2] = T(tmpPtr[2]*factor);
          tmpPtr += 4; 
          outPtr += outC;
          }
        }
      else 
        {
        for (int idxX = extent[0]; idxX <= extent[1]; idxX++)
          {
          double factor = 0.0;
          if (tmpPtr[1] != 0)
            {
            factor = 1.0/tmpPtr[1];
            }
          outPtr[0] = T(tmpPtr[0]*factor);
          tmpPtr += 2;
          outPtr += outC;
          }
        }

      tmpPtr += tmpIncY;
      outPtr += outIncY;
      }
    tmpPtr += tmpIncZ;
    outPtr += outIncZ;
    }
}


//----------------------------------------------------------------------------
// This method is passed a input and output regions, and executes the filter
// algorithm to fill the output from the inputs.
// It just executes a switch statement to call the correct function for
// the regions data types.
void vtkImageBlend::ThreadedRequestData (  
  vtkInformation * vtkNotUsed( request ), 
  vtkInformationVector** inputVector, 
  vtkInformationVector * vtkNotUsed( outputVector ),
  vtkImageData ***inData, 
  vtkImageData **outData,
  int outExt[6], int id)
{
  int extent[6];
  void *inPtr;
  void *outPtr;

  double opacity;

  vtkImageData *tmpData = NULL;
  
  // check
  if (inData[0][0]->GetNumberOfScalarComponents() > 4)
    {
    vtkErrorMacro("The first input can have a maximum of four components");
    return;
    }

  // init
  switch (this->BlendMode)
    {
    case VTK_IMAGE_BLEND_MODE_NORMAL:
      // copy the first image directly to the output
      vtkDebugMacro("Execute: copy input 0 to the output.");
      vtkImageBlendCopyData(inData[0][0], outData[0], outExt);
      break;

    case VTK_IMAGE_BLEND_MODE_COMPOUND:
      tmpData = vtkImageData::New();
      if (tmpData == NULL) 
        {
        vtkErrorMacro(<< "Execute: Unable to allocate memory");
        return;
        }
      tmpData->SetExtent(outExt);
      tmpData->SetNumberOfScalarComponents(
        (outData[0]->GetNumberOfScalarComponents() >= 3 ? 3 : 1) + 1);
      tmpData->SetScalarType(VTK_DOUBLE);
      tmpData->AllocateScalars();
      memset((void *)tmpData->GetScalarPointer(), 0, 
             (outExt[1] - outExt[0] + 1) * 
             (outExt[3] - outExt[2] + 1) * 
             (outExt[5] - outExt[4] + 1) *
             tmpData->GetNumberOfScalarComponents() * 
             tmpData->GetScalarSize());
      break;

    default:
      vtkErrorMacro(<< "Execute: Unknown blending mode");
    }

  // process each input
  int first_index = (this->BlendMode == VTK_IMAGE_BLEND_MODE_NORMAL ? 1 : 0);
  for (int idx1 = first_index; 
       idx1 < this->GetNumberOfInputConnections(0); ++idx1)
    {
    if (inData[0][idx1] != NULL)
      {

      // RGB with RGB, greyscale with greyscale
      if ((inData[0][idx1]->GetNumberOfScalarComponents()+1)/2 == 2 &&
          (inData[0][0]->GetNumberOfScalarComponents()+1)/2 == 1)
        {
        vtkErrorMacro("input has too many components, can't blend RGB data \
                       into greyscale data");
        continue;
        }
      
      // this filter expects that input is the same type as output.
      if (inData[0][idx1]->GetScalarType() != outData[0]->GetScalarType())
        {
        vtkErrorMacro(<< "Execute: input" << idx1 << " ScalarType (" << 
        inData[0][idx1]->GetScalarType() << 
        "), must match output ScalarType (" << outData[0]->GetScalarType() 
        << ")");
        continue;
        }
      
      // input extents
      vtkInformation *inInfo = 
        inputVector[0]->GetInformationObject(idx1);
      int *inWextent = 
        inInfo->Get(vtkStreamingDemandDrivenPipeline::WHOLE_EXTENT());
      this->InternalComputeInputUpdateExtent(extent, outExt, inWextent);

      int skip = 0;
      for (int i = 0; i < 3; i++)
        {
        if (outExt[2*i+1] < extent[2*i] || outExt[2*i] > extent[2*i+1])
          {
          // extents don't overlap, skip this input
          skip = 1; 
          }
        }
      
      if (skip) 
        {
        vtkDebugMacro("Execute: skipping input.");
        continue;
        }
      
      opacity = this->GetOpacity(idx1);
          
      inPtr = inData[0][idx1]->GetScalarPointerForExtent(extent);

      // vtkDebugMacro("Execute: " << idx1 << "=>" << extent[0] << ", " << extent[1] << " / " << extent[2] << ", " << extent[3] << " / " << extent[4] << ", " << extent[5]);
      
      switch (this->BlendMode)
        {
        case VTK_IMAGE_BLEND_MODE_NORMAL:
          outPtr = outData[0]->GetScalarPointerForExtent(extent);  
          // for performance reasons, use a special method for unsigned char
          if (inData[0][idx1]->GetScalarType() == VTK_UNSIGNED_CHAR)
            {
            vtkImageBlendExecuteChar(this, extent,
                                     inData[0][idx1], (unsigned char *)(inPtr),
                                     outData[0], (unsigned char *)(outPtr),
                                     opacity, id);
            }
          else
            {
            switch (inData[0][idx1]->GetScalarType())
              {
              vtkTemplateMacro(
                vtkImageBlendExecute(this, extent,
                                     inData[0][idx1], (VTK_TT *)(inPtr),
                                     outData[0], (VTK_TT *)(outPtr), 
                                     opacity, id));
              default:
                vtkErrorMacro(<< "Execute: Unknown ScalarType");
                return;
              }
            }
          break;

        case VTK_IMAGE_BLEND_MODE_COMPOUND:
          switch (inData[0][idx1]->GetScalarType())
            {
            vtkTemplateMacro(
              vtkImageBlendCompoundExecute(this, 
                                           extent,
                                           inData[0][idx1], 
                                           (VTK_TT *)(inPtr), 
                                           tmpData, 
                                           opacity,
                                           this->CompoundThreshold));
            default:
              vtkErrorMacro(<< "Execute: Unknown ScalarType");
              return;
            }
          break;

        default:
          vtkErrorMacro(<< "Execute: Unknown blending mode");
        }
      }
    }

  // conclude
  switch (this->BlendMode)
    {
    case VTK_IMAGE_BLEND_MODE_NORMAL:
      break;

    case VTK_IMAGE_BLEND_MODE_COMPOUND:
      outPtr = outData[0]->GetScalarPointerForExtent(outExt);
      switch (outData[0]->GetScalarType())
        {
        vtkTemplateMacro(
          vtkImageBlendCompoundTransferExecute(this, 
                                               outExt,
                                               outData[0], 
                                               (VTK_TT *)(outPtr), 
                                               tmpData));
        default:
          vtkErrorMacro(<< "Execute: Unknown ScalarType");
          return;
        }
      tmpData->Delete();
      break;

    default:
      vtkErrorMacro(<< "Execute: Unknown blending mode");
    }
}


//----------------------------------------------------------------------------
void vtkImageBlend::PrintSelf(ostream& os, vtkIndent indent)
{
  this->Superclass::PrintSelf(os, indent);
  int i;
  for (i = 0; i < this->OpacityArrayLength; i++)
    {
    os << indent << "Opacity(" << i << "): " << this->GetOpacity(i) << endl; 
    }
  os << indent << "Stencil: " << this->GetStencil() << endl;
  os << indent << "BlendMode: " << this->GetBlendModeAsString() << endl
     << indent << "CompoundThreshold: " << this->CompoundThreshold << endl;
}

//----------------------------------------------------------------------------
int vtkImageBlend::FillInputPortInformation(int port, vtkInformation* info)
{
  if (port == 0)
    {
    info->Set(vtkAlgorithm::INPUT_REQUIRED_DATA_TYPE(), "vtkImageData");
    info->Set(vtkAlgorithm::INPUT_IS_REPEATABLE(), 1);
    }
  if (port == 1)
    {
    info->Set(vtkAlgorithm::INPUT_REQUIRED_DATA_TYPE(), "vtkImageStencilData");
    // the stencil input is optional
    info->Set(vtkAlgorithm::INPUT_IS_OPTIONAL(), 1);
    }
  return 1;
}