topic Re: Cross correlation does not work in Intel® Integrated Performance Primitives

Cross correlation does not work

shyweissman — Fri, 03 Feb 2006 23:38:18 GMT

Here is my sample code that runs but return zero on all return matrix

int

_tmain(int argc, _TCHAR* argv[])

{

IppiSize srcRoiSize, tplRoiSize, SizeMat;

Ipp8u* p_img_src, *p_img_templ,*imgMatr;

srcRoiSize.height = 64;

srcRoiSize.width = 64;

tplRoiSize.height = 32;

tplRoiSize.width = 32;

SizeMat.height = 33;

SizeMat.width = 33;

int StepByteSrc,StepByteTempl,stepBytes;

int max_x,max_y;

Ipp8u max_val;

p_img_src = ippiMalloc_8u_C1(64, 64,&StepByteSrc );

p_img_templ = ippiMalloc_8u_C1(32, 32,&StepByteTempl );

imgMatr = ippiMalloc_8u_C1(33, 33,&stepBytes );

memset((void*)p_img_src,0x80,64*64);

memset((void*)p_img_templ,0x80,32*32);

// memset((void*)imgMatr,0,stepBytes*33);

IppStatus Corr_status =

ippiCrossCorrValid_NormLevel_8u_C1RSfs(p_img_src,StepByteSrc, srcRoiSize,

p_img_templ,StepByteTempl ,tplRoiSize, imgMatr, stepBytes, 0);

ippiMaxIndx_8u_C1R(imgMatr, stepBytes, SizeMat, &max_val, &max_x, &max_y);

ippiFree(imgMatr);

return 0;

}

Intel_C_Intel — Mon, 06 Feb 2006 19:20:17 GMT

Correlation coeffs are

Intel_C_Intel — Mon, 06 Feb 2006 19:20:18 GMT

Correlation coeffs are less

Intel_C_Intel — Mon, 06 Feb 2006 19:21:41 GMT

Abs value of correlation coeffs are less than 1, so 8u results will be always 0 with a scale factor 0. Try scale factor = -8

shyweissman — Mon, 06 Feb 2006 20:23:56 GMT

It does not work with -8 eigther.

It always give matrix of zeros unless bytes of template and image contain more than one value ie 0 and 1.

If all bytes of template or image are equall the matrix is all zero.

Intel_C_Intel — Mon, 06 Feb 2006 20:41:30 GMT

Please look to cross correlation folmula in the manual.

The image mean is subtracted from the image ie zero result will be for constant image or template