Method CalcHistogram

Samples/NiUserSelection/UserTracker.cpp:168–213

void UserTracker::CalcHistogram(const XnDepthPixel* pDepth, XnUInt16 xRes,XnUInt16 yRes)
{
	XnDepthPixel zRes = m_DepthGenerator.GetDeviceMaxDepth() + 1;
    if(s_pDepthHist==NULL)
        s_pDepthHist=XN_NEW_ARR(float,zRes); // initialize the histogram's buffer


    XnUInt32 nNumberOfPoints = 0; // will hold the number of points in the histogram
    XnDepthPixel nValue; // will hold temporary pixel values. 

    xnOSMemSet(s_pDepthHist, 0, zRes*sizeof(float)); // clear everything, we start from scratch

    // calculate the basic histogram (i.e. the buffer in position X will hold the number of pixels
    // in the depth map which have a value of X.
    // NOTE: a value of 0 is not counted (i.e. m_pDepthHist[0] will always be 0) and we assume
    // MAX_DEPTH is large enough so that we never have a value larger than it.
    for (XnUInt16 nY=0; nY<yRes; nY++)
    {
        for (XnUInt16 nX=0; nX<xRes; nX++)
        {
            nValue = *pDepth;

            if (nValue != 0)
            {
                s_pDepthHist[nValue]++;
                nNumberOfPoints++;
            }
            pDepth++;
        }
    }

    if(nNumberOfPoints==0)
        return; // nothing to do, there are no values.
    // turn the histogram to a cumulative histogram
    for (XnUInt16 nIndex=1; nIndex<zRes; nIndex++)
    {
        s_pDepthHist[nIndex] += s_pDepthHist[nIndex-1];
    }
    // normalize the values to a value between 0 and 256. This is the color we want to see elements
    // of this value as (multiplier).

    for (XnUInt16 nIndex=1; nIndex<zRes; nIndex++)
    {
        s_pDepthHist[nIndex] = (256 * (1.0f - (s_pDepthHist[nIndex] / nNumberOfPoints)));
    }
}

void UserTracker::FillTexture(unsigned char* pTexBuf, XnUInt16 nTexWidth, XnUInt16 /*nTexHeight*/, XnBool bDrawBackground)
{