Method transform

deps/opencv/modules/core/src/matmul.cpp:1761–1830

}

void cv::transform( InputArray _src, OutputArray _dst, InputArray _mtx )
{
    Mat src = _src.getMat(), m = _mtx.getMat();
    int depth = src.depth(), scn = src.channels(), dcn = m.rows;
    CV_Assert( scn == m.cols || scn + 1 == m.cols );
    bool isDiag = false;

    _dst.create( src.size(), CV_MAKETYPE(depth, dcn) );
    Mat dst = _dst.getMat();

    int mtype = depth == CV_32S || depth == CV_64F ? CV_64F : CV_32F;
    AutoBuffer<double> _mbuf;
    double* mbuf;

    if( !m.isContinuous() || m.type() != mtype || m.cols != scn + 1 )
    {
        _mbuf.allocate(dcn*(scn+1));
        mbuf = (double*)_mbuf;
        Mat tmp(dcn, scn+1, mtype, mbuf);
        memset(tmp.data, 0, tmp.total()*tmp.elemSize());
        if( m.cols == scn+1 )
            m.convertTo(tmp, mtype);
        else
        {
            Mat tmppart = tmp.colRange(0, m.cols);
            m.convertTo(tmppart, mtype);
        }
        m = tmp;
    }
    else
        mbuf = (double*)m.data;

    if( scn == dcn )
    {
        int i, j;
        double eps = mtype == CV_32F ? FLT_EPSILON : DBL_EPSILON;

        if( scn == 1 )
        {
            double alpha, beta;
            if( mtype == CV_32F )
                alpha = m.at<float>(0), beta = m.at<float>(1);
            else
                alpha = m.at<double>(0), beta = m.at<double>(1);
            src.convertTo(dst, dst.type(), alpha, beta);
            return;
        }

        for( i = 0, isDiag = true; isDiag && i < scn; i++ )
        {
            for( j = 0; isDiag && j < scn; j++ )
            {
                double v = mtype == CV_32F ? m.at<float>(i, j) : m.at<double>(i, j);
                if( i != j && fabs(v) > eps )
                    isDiag = false;
            }
        }
    }