(C++ VCL) Convert a bitmap to a matrix

template <class T> std::vector<std::vector<T> > GetMatrix(const TImage * const image)
{
  assert(image!=0);
  const T zero = static_cast<T>(0.0);
  const int width = image->Width;
  const int height = image->Height;
  std::vector<std::vector<T> > matrix(width,std::vector<double>(height,zero));
  for (int y=0; y!=height; ++y)
  {
    const unsigned char * const line
      = static_cast<const unsigned char *>(image->Picture->Bitmap->ScanLine[y]);
    for (int x=0; x!=width; ++x)
    {
      Assert(x < static_cast<int>(matrix.size()));
      Assert(y < static_cast<int>(matrix[x].size()));
      const T grey = static_cast<T>(
        line[x*3+0] + line[x*3+1] + line[x*3+2])
        / static_cast<T>(3.0);
      matrix[x][y] = grey;
    }
  }
  return matrix;
}

Code links

• assert
• const