Method MagnifyImageLinear

Rendering/Parallel/vtkParallelRenderManager.cxx:1246–1373

#define VTK_VEC_DIV_2(intvector) (((intvector) >> 1) & 0x7F7F7F7F)

void vtkParallelRenderManager::MagnifyImageLinear(vtkUnsignedCharArray* fullImage,
  const int fullImageSize[2], vtkUnsignedCharArray* reducedImage, const int reducedImageSize[2],
  const int fullImageViewport[4], const int reducedImageViewport[4])
{
  int xmag, ymag;
  int x, y;
  int srcComp = reducedImage->GetNumberOfComponents();

  // Allocate full image so all pixels are on 4-byte integer boundaries.
  fullImage->SetNumberOfComponents(4);
  fullImage->SetNumberOfTuples(fullImageSize[0] * fullImageSize[1]);

  int destLeft, destBottom, destWidth, destHeight;
  if (fullImageViewport)
  {
    destLeft = fullImageViewport[0];
    destBottom = fullImageViewport[1];
    destWidth = fullImageViewport[2] - fullImageViewport[0];
    destHeight = fullImageViewport[3] - fullImageViewport[1];
  }
  else
  {
    destLeft = destBottom = 0;
    destWidth = fullImageSize[0];
    destHeight = fullImageSize[1];
  }

  int srcLeft, srcBottom, srcWidth, srcHeight;
  if (reducedImageViewport)
  {
    srcLeft = reducedImageViewport[0];
    srcBottom = reducedImageViewport[1];
    srcWidth = reducedImageViewport[2] - reducedImageViewport[0];
    srcHeight = reducedImageViewport[3] - reducedImageViewport[1];
  }
  else
  {
    srcLeft = srcBottom = 0;
    srcWidth = reducedImageSize[0];
    srcHeight = reducedImageSize[1];
  }

  // Guess x and y magnification.  Round up to ensure we do not try to
  // read data from the image data that does not exist.
  xmag = (destWidth + srcWidth - 1) / srcWidth;
  ymag = (destHeight + srcHeight - 1) / srcHeight;

  // For speed, we only magnify by powers of 2.  Round up to the nearest
  // power of 2 to ensure that the reduced image is large enough.
  int powOf2;
  for (powOf2 = 1; powOf2 < xmag; powOf2 <<= 1)
  {
  }
  xmag = powOf2;
  for (powOf2 = 1; powOf2 < ymag; powOf2 <<= 1)
  {
  }
  ymag = powOf2;