Method Mat

deps/opencv/modules/core/src/matrix.cpp:266–317

Mat::Mat(const Mat& m, const Range& _rowRange, const Range& _colRange) : size(&rows)
{
    initEmpty();
    CV_Assert( m.dims >= 2 );
    if( m.dims > 2 )
    {
        AutoBuffer<Range> rs(m.dims);
        rs[0] = _rowRange;
        rs[1] = _colRange;
        for( int i = 2; i < m.dims; i++ )
            rs[i] = Range::all();
        *this = m(rs);
        return;
    }

    *this = m;
    try
    {
        if( _rowRange != Range::all() && _rowRange != Range(0,rows) )
        {
            CV_Assert( 0 <= _rowRange.start && _rowRange.start <= _rowRange.end
                       && _rowRange.end <= m.rows );
            rows = _rowRange.size();
            data += step*_rowRange.start;
            flags |= SUBMATRIX_FLAG;
        }

        if( _colRange != Range::all() && _colRange != Range(0,cols) )
        {
            CV_Assert( 0 <= _colRange.start && _colRange.start <= _colRange.end
                       && _colRange.end <= m.cols );
            cols = _colRange.size();
            data += _colRange.start*elemSize();
            flags &= cols < m.cols ? ~CONTINUOUS_FLAG : -1;
            flags |= SUBMATRIX_FLAG;
        }
    }
    catch(...)
    {
        release();
        throw;
    }

    if( rows == 1 )
        flags |= CONTINUOUS_FLAG;

    if( rows <= 0 || cols <= 0 )
    {
        release();
        rows = cols = 0;
    }
}


Mat::Mat(const Mat& m, const Rect& roi)