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Beginner
19 Views

ippiHistogram_8u_C1R problem

Dear all,

I am trying to use ippiHistogram. The problem is - the last (256) byte of histogram result buffer is not filled by ippiHistogram_8u_C1R. 
I have tried to use ippiHistogramInit instead of ippiHistogramUniformInit - the result is the same.
Previously I used iplComputeHisto function - it had worked correctly. 
For example iplComputeHisto returns pHistVec[255] = 1226, but ippiHistogram_8u_C1R returns pHistVec[255] = 1393896807 

I use IPPI version 9 Update 1.

Please, explain, how can I get last histogram value? Thank you!

Here is the code:

IppiSize roi = {image->width, image->height};
int nChannels = image->nChannels;
const int histLen = 255;
int nLevels[] = { histLen+1 };
Ipp32f lowerLevel[] = {0};
Ipp32f upperLevel[] = {255};
Ipp32f pLevels[histLen+1], *ppLevels[1];
int sizeHistObj = 0;
int sizeBuffer = 0;
IppiHistogramSpec* pHistObj = NULL;
Ipp8u* pBuffer = NULL;
Ipp32u pHistVec[histLen + 1];

bool errorInCycle = false;

IppStatus sts = ippiHistogramGetBufferSize(ipp8u, roi, nLevels, nChannels, 0, &sizeHistObj, &sizeBuffer);
if(sts != ippStsNoErr)
{
	return;
}

pHistObj = (IppiHistogramSpec*)ippsMalloc_8u(sizeHistObj);
if(pHistObj == NULL)
{
	return;
}

pBuffer = (Ipp8u*)ippsMalloc_8u(sizeBuffer);
if(pHistObj == NULL)
{
	ippsFree( pHistObj );
	return;
}

sts = ippiHistogramUniformInit(ipp8u, lowerLevel, upperLevel, nLevels, nChannels, pHistObj);
if(sts != ippStsNoErr)
{
	ippsFree( pHistObj );
	ippsFree( pBuffer );
	return;
}

sts = ippiHistogram_8u_C1R((const Ipp8u *) image->imageData, image->widthStep, roi, pHistVec, pHistObj, pBuffer);
if(sts != ippStsNoErr)
{
	ippsFree( pHistObj );
	ippsFree( pBuffer );
	return;
}

std::stringstream ssTemp;
ssTemp << "Hist: ";
for(int i=0; i < 256; i++) 
{
	ssTemp << i << " = " << pHistVec << ",";
}
OutputDebugString((char *)ssTemp.str().c_str());

Kind regards
Dmitry

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2 Replies
Highlighted
Beginner
19 Views

Hi ,I too am getting sizeBuffer = 0 from ippiHistogramGetBufferSize

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Highlighted
New Contributor I
19 Views

The API is nuts (or at least counter-intuitive). For 256 histogram entries, you have to pass 257 as the nLevels parameter of  ippiHistogramUniformInit. This is for analogy with non-uniform histograms, but very tricky. The sample code in the documentation is wrong too.

Regards,

Adriaan van Os

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