Function vtkOpenGLImageMapperRenderShort

Rendering/OpenGL2/vtkOpenGLImageMapper.cxx:254–376

template <class T>
void vtkOpenGLImageMapperRenderShort(vtkOpenGLImageMapper* self, vtkImageData* data, T* dataPtr,
  double shift, double scale, vtkViewport* viewport)
{
  vtkOpenGLClearErrorMacro();

  int inMin0 = self->DisplayExtent[0];
  int inMax0 = self->DisplayExtent[1];
  int inMin1 = self->DisplayExtent[2];
  int inMax1 = self->DisplayExtent[3];

  int width = inMax0 - inMin0 + 1;
  int height = inMax1 - inMin1 + 1;

  vtkIdType tempIncs[3];
  data->GetIncrements(tempIncs);
  vtkIdType inInc1 = tempIncs[1];

  int bpp = data->GetNumberOfScalarComponents();

  double range[2];
  data->GetPointData()->GetScalars()->GetDataTypeRange(range);

  auto ostate = static_cast<vtkOpenGLRenderWindow*>(viewport->GetVTKWindow())->GetState();
  ostate->vtkglPixelStorei(GL_UNPACK_ALIGNMENT, 1);

  // Find the number of bits to use for the fraction:
  // continue increasing the bits until there is an overflow
  // in the worst case, then decrease by 1.
  // The "*2.0" and "*1.0" ensure that the comparison is done
  // with double-precision math.
  int bitShift = 0;
  double absScale = std::abs(scale);

  while ((static_cast<long>(1 << bitShift) * absScale) * 2.0 * USHRT_MAX < INT_MAX * 1.0)
  {
    bitShift++;
  }
  bitShift--;
  bitShift = std::max(bitShift, 0);

  long sscale = static_cast<long>(scale * (1 << bitShift));
  long sshift = static_cast<long>(sscale * shift);
  /* should do proper rounding, as follows:
  long sscale = (long) floor(scale*(1 << bitShift) + 0.5);
  long sshift = (long) floor((scale*shift + 0.5)*(1 << bitShift));
  */
  long val;
  unsigned char tmp;

  T* inPtr = dataPtr;
  T* inPtr1 = inPtr;

  int i;
  int j = height;

  unsigned char* newPtr;
  if (bpp < 4)
  {