Documentation of FilterColumn is wrong

Hernßn_B_ — Thu, 21 Aug 2008 15:29:23 GMT

The example shown in the documentation for ippiFilterColumn is wrong for many reasons:

1.- the border is not being considered. As shown in the example, memory outside the allocated space will be read. This means also that the first and last rows of the destination image will not contain meaningful information.
2.- According to the result you are showing, yAnchor must be 1 and not 2.
3.- The example is terrible bad, because you are using 8u as data type but the kernel filter has a negative value.
4.- The result should be 0 everywhere, since you are using "Sobel" kernel and the data does not contain any "gradient" in vertical direction.

Something more appropriate will be:

______________________________________________
Ipp16s src[4*3] = {
1, 0, 0, 4,
0, 0, 3, 4,
0, 2, 3, 1
};

Ipp16s dst[4*3] =
{
0, 0, 0, 0,
0, 0, 0, 0,
0, 0, 0, 0
};

IppiSize srcRoi;
srcRoi.width = 4;
srcRoi.height = 1;
Ipp32s kern[] = { 1, 2, -3 };
int kernelSize = 3;
int yAnchor = 1;
int divisor = 1;

ippiFilterColumn_16s_C1R ( src+4, 4*sizeof(Ipp16s), dst+4, 4*sizeof(Ipp16s), srcRoi, kern, kernelSize,
yAnchor, divisor);

for (int i = 0; i < 3; ++i)
{
for (int j = 0; j < 4; ++j)
{
printf("dst[%i][%i] = %i ",
i, j, dst[i*4+j]);
}
}
______________________________________________

Result:

dst[0][0] = 0
dst[0][1] = 0
dst[0][2] = 0
dst[0][3] = 0
dst[1][0] = -3
dst[1][1] = 2
dst[1][2] = 9
dst[1][3] = -3
dst[2][0] = 0
dst[2][1] = 0
dst[2][2] = 0
dst[2][3] = 0

Regards,

Hernn Badino

Re: Documentation of FilterColumn is wrong

Vladimir_Dudnik — Wed, 27 Aug 2008 16:34:50 GMT

Hello,

thanks for pointing to this. We will correct sample.

Regards,
Vladimir

topic Documentation of FilterColumn is wrong in Intel® Integrated Performance Primitives

Documentation of FilterColumn is wrong

Re: Documentation of FilterColumn is wrong