opencv histPrepareImages

static void histPrepareImages( const Mat* images, int nimages, const int* channels,
                               const Mat& mask, int dims, const int* histSize,
                               const float** ranges, bool uniform,
                               std::vector<uchar*>& ptrs, std::vector<int>& deltas,
                               Size& imsize, std::vector<double>& uniranges )
{
    int i, j, c;
    CV_Assert( channels != 0 || nimages == dims );

    imsize = images[0].size();
    int depth = images[0].depth(), esz1 = (int)images[0].elemSize1();
    bool isContinuous = true;

    ptrs.resize(dims + 1);
    deltas.resize((dims + 1)*2);

    for( i = 0; i < dims; i++ )
    {
        if(!channels)
        {
            j = i;
            c = 0;
            CV_Assert( images[j].channels() == 1 );
        }
        else
        {
            c = channels[i];
            CV_Assert( c >= 0 );
            for( j = 0; j < nimages; c -= images[j].channels(), j++ )
                if( c < images[j].channels() )
                    break;
            CV_Assert( j < nimages );
        }

        CV_Assert( images[j].size() == imsize && images[j].depth() == depth );
        if( !images[j].isContinuous() )
            isContinuous = false;
        ptrs[i] = images[j].data + c*esz1;
        deltas[i*2] = images[j].channels();
        deltas[i*2+1] = (int)(images[j].step/esz1 - imsize.width*deltas[i*2]);
    }

    if( !mask.empty() )
    {
        CV_Assert( mask.size() == imsize && mask.channels() == 1 );
        isContinuous = isContinuous && mask.isContinuous();
        ptrs[dims] = mask.data;
        deltas[dims*2] = 1;
        deltas[dims*2 + 1] = (int)(mask.step/mask.elemSize1());
    }

#ifndef HAVE_TBB
    if( isContinuous )
    {
        imsize.width *= imsize.height;
        imsize.height = 1;
    }
#endif

    if( !ranges )
    {
        CV_Assert( depth == CV_8U );

        uniranges.resize( dims*2 );
        for( i = 0; i < dims; i++ )
        {
            uniranges[i*2] = histSize[i]/256.;
            uniranges[i*2+1] = 0;
        }
    }
    else if( uniform )
    {
        uniranges.resize( dims*2 );
        for( i = 0; i < dims; i++ )
        {
            CV_Assert( ranges[i] && ranges[i][0] < ranges[i][1] );
            double low = ranges[i][0], high = ranges[i][1];
            double t = histSize[i]/(high - low);
            uniranges[i*2] = t;
            uniranges[i*2+1] = -t*low;
        }
    }
    else
    {
        for( i = 0; i < dims; i++ )
        {
            size_t n = histSize[i];
            for(size_t k = 0; k < n; k++ )
                CV_Assert( ranges[i][k] < ranges[i][k+1] );
        }
    }
}