/** @file inthist.tc
 ** @brief vl_intist.c helper
 ** @author Andrea Vedaldi
 **/

/*
Copyright (C) 2007-12 Andrea Vedaldi and Brian Fulkerson.
All rights reserved.

This file is part of the VLFeat library and is made available under
the terms of the BSD license (see the COPYING file).
*/

#define JOIN_(a,b) a ## b
#define JOIN(a,b) JOIN_(a,b)

#undef INTEGRAL
#define INTEGRAL JOIN(integral_, SFX)

/*
   This function is 'transpose safe': The integral histogram SRC can
   be either column major or row major, as long as WIDTH is the
   fastest varying dimension.
*/
void INTEGRAL (T* dst,
               int dstStride,
               T const* src,
               int srcWidth, int srcHeight, int srcStride)
{
  int x, y ;
  *dst = *src ;
  dst += 1 ;
  src += 1 ;

  for (x = 1 ; x < srcWidth ; ++ x) {
    *dst = *(dst - 1)  + *src ;
    dst += 1 ;
    src += 1 ;
  }

  for (y = 1 ; y < srcHeight ; ++ y) {
    dst += dstStride - srcWidth ;
    src += srcStride - srcWidth ;

    *dst = *(dst - dstStride) + *src ;
    dst += 1 ;
    src += 1 ;

    for (x = 1 ; x < srcWidth ; ++ x) {
      *dst =  *(dst - dstStride) - *(dst - dstStride - 1) +  *(dst - 1)  + *src ;
      dst += 1 ;
      src += 1 ;
    }
  }
}