Help with cross correlation

daniel_pandian — Thu, 01 Nov 2007 21:12:06 GMT

Hi
I am tring to use ippiCrossCorrValid_Norm_16u32f_C1R function to calculate cross correlation between a square template and rectangular search window. Some how my code works only if i take a square seach window and not with rectangular search window.

here i give a small sample code that create problem,

int blockSize=3; // template size 3x3

int searchWSizeX=9;
int searchWSizeY=5;

int resultWindowSizeX=7;
int resultWindowSizeY=3;
int resultWindowTSize=resultWindowSizeX*resultWindowSizeY;

// i tried with ippmalloc, but i got same result

// template
unsigned short temp[]={697,666,618,666,669,591,666,591,512};

//search window
unsigned short image[]={669, 669, 690, 690, 693, 673, 710, 669, 659,
690, 663, 669, 714, 687, 687, 700, 680, 683,
700, 673, 700, 731, 690, 707, 727, 690, 666,
693, 714, 687, 714, 680, 669, 676, 721, 683,
707, 666, 704, 707, 618, 663, 700, 704, 680

};
IppStatus status;
int tplStep=blockSize*sizeof(Ipp16u); // ipp16u nothing but unsigned short
IppiSize tplRoiSize,srcRoiSize;
tplRoiSize.height=blockSize;
tplRoiSize.width=blockSize;

int srcStep=searchWSizeX*sizeof(Ipp16u);
srcRoiSize.height=searchWSizeY;
srcRoiSize.width=searchWSizeX;
Ipp32f* pDst;
pDst=ippsMalloc_32f(resultWindowTSize);
int dstStep=resultWindowSizeX*sizeof(Ipp32f);

status=ippiCrossCorrValid_Norm_16u32f_C1R(image,srcStep,srcRoiSize,temp,tplStep,tplRoiSize,pDst,dstStep);
if(status==ippStsNoErr)
{
&nbs p; printf("No error");
}
else
{
printf("error number %d ",status);
}
// print the result
for(int r=0;r {
for(int s=0;s {

fprintf(fp1,"%f ",pDst[resultWindowSizeY*r +s]);
}
fprintf(fp1," ");
}

ippsFree(temp);
ippsFree(image)

I expect to get some result of size 7x3 having the following values as ( i got first 3x3 values hand calculated and verified with matlab)

9.95402310773594E-01	9.93216121828153E-01	9.95709101211673E-01
9.95513545974447E-01	9.94066090279466E-01	9.96289650300696E-01
9.96263594187887E-01	9.94619810815054E-01	9.98277076699970E-01

I am getting the first line of the result as correct, but last 2 lines incorrect.

Anybody please help me

Thank you
Daniel

Re: Help with cross correlation

Vladimir_Dudnik — Mon, 05 Nov 2007 04:38:30 GMT

Hello Daniel,

our expert recommends you to try the following piece of code (this is reference code according to the formulae and provides results identical with IPP. We do not know how it was implemented in MATLAB)

#include 
#include "ipp.h"
IppStatus altCrossCorrValid_Norm_16u32f_C1R(
  Ipp16u*  src,
  int      srcStep,
  IppiSize srcSize,
Ipp16u*  tpl,
  int      tplStep,
  IppiSize tplSize,
Ipp32f*  dst,
  int      dstStep)
{
 int elmSize = sizeof(Ipp16u);
 int sStep = srcStep/elmSize;
 int tStep = tplStep/elmSize;
 int rStep = dstStep/4;
 int rWidth = srcSize.width - tplSize.width + 1;
 int rHeight = srcSize.height - tplSize.height + 1;
 int tWidth = tplSize.width;
 int tHeight = tplSize.height;
 Ipp32f thresh;
 Ipp16u* tmpSrc, *tmpTpl;
 double tplL2;
 int i, j, hT, wT;
ippiNorm_L2_16u_C1R( tpl, tplStep, tplSize, &tplL2 );
 if( elmSize > 2 )
    thresh = 1;
 else
    thresh = 5e-4;
 for( i = 0; i < rHeight; i++)
  {
 for( j = 0; j < rWidth; j++)
    {
 Ipp32f tmpSum = 0.0f;
 Ipp32f tmpSqrt = 0.0f;
 tmpSrc = src + j;
 tmpTpl = tpl;
 for( hT = 0; hT < tHeight; hT++)
      {
 for( wT = 0; wT < tWidth; wT++)
        {
 tmpSum  += (Ipp32f)tmpSrc[wT] * (Ipp32f)tmpTpl[wT];
 tmpSqrt += (Ipp32f)tmpSrc[wT] * (Ipp32f)tmpSrc[wT];
 } /* for */< p="">
 tmpSrc += sStep;
 tmpTpl += tStep;
 } /* for */
 if( tplL2 < thresh )
        tplL2 = thresh;
 if( tmpSqrt < thresh )
        tmpSqrt = thresh;
 tmpSqrt = tmpSqrt * (Ipp32f)(tplL2 * tplL2);
 tmpSqrt = (Ipp32f)(1.0/sqrt(tmpSqrt));
 dst = tmpSum * tmpSqrt;
 } /* for */
 src += sStep;
 dst += rStep;
 } /* for */
 return (IppStatus)0;
}
int main()
{
int blockSize = 3;// template size 3x3

int searchWSizeX = 9;
int searchWSizeY = 5;
int resultWindowSizeX = 7;
int resultWindowSizeY = 3;
int resultWindowTSize = resultWindowSizeX * resultWindowSizeY;
int r, s;
// i tried with ippmalloc, but i got same result
// template
unsigned short temp[] =
  {
    697, 666, 618, 666, 669, 591, 666, 591, 512
  };
//search window 
 unsigned short image[] =
  {
    669, 669, 690, 690, 693, 673, 710, 669, 659,
 690, 663, 669, 714, 687, 687, 700, 680, 683,
 700, 673, 700, 731, 690, 707, 727, 690, 666,
 693,&nb
sp; 714, 687, 714, 680, 669, 676, 721, 683,
 707, 666, 704, 707, 618, 663, 700, 704, 680
 
};
IppStatus status;
 int tplStep = blockSize * sizeof(Ipp16u); // ipp16u nothing but unsigned short
IppiSize tplRoiSize, srcRoiSize;
int srcStep = searchWSizeX * sizeof(Ipp16u);
int dstStep = resultWindowSizeX * sizeof(Ipp32f);
Ipp32f* pDst;
tplRoiSize.height = blockSize;
tplRoiSize.width  = blockSize;
srcRoiSize.height = searchWSizeY;
srcRoiSize.width  = searchWSizeX;
pDst = ippsMalloc_32f(resultWindowTSize);
status=altCrossCorrValid_Norm_16u32f_C1R(image,srcStep,srcRoiSize,temp,tplStep,tplRoiSize,pDst,dstStep);
// status=ippiCrossCorrValid_Norm_16u32f_C1R(image,srcStep,srcRoiSize,temp,tplStep,tplRoiSize,pDst,dstStep);
if(status == ippStsNoErr)
{
printf("No error
");
}
else
{
printf("error number %d
",status);
}
// print the result
  for(r = 0; r < resultWindowSizeY; r++)
{ 
for(s = 0; s < resultWindowSizeX; s++)
{
printf("%f	",pDst[resultWindowSizeY*r +s]);
}
 printf("	 
");
}
ippsFree(temp);
ippsFree(image);
return 0;
}

Regards,
Vladimir

topic Help with cross correlation in Intel® Integrated Performance Primitives

Help with cross correlation

Re: Help with cross correlation