Function icvFetchContourEx_32s

deps/opencv/modules/imgproc/src/contours.cpp:855–987

static void
icvFetchContourEx_32s( int*                 ptr,
                       int                  step,
                       CvPoint              pt,
                       CvSeq*               contour,
                       int                  _method,
                       CvRect*              _rect )
{
    int         deltas[16];
    CvSeqWriter writer;
    int        *i0 = ptr, *i1, *i3, *i4;
    CvRect      rect;
    int         prev_s = -1, s, s_end;
    int         method = _method - 1;
    const int   right_flag = INT_MIN;
    const int   new_flag = (int)((unsigned)INT_MIN >> 1);
    const int   value_mask = ~(right_flag | new_flag);
    const int   ccomp_val = *i0 & value_mask;
    const int   nbd0 = ccomp_val | new_flag;
    const int   nbd1 = nbd0 | right_flag;

    assert( (unsigned) _method <= CV_CHAIN_APPROX_SIMPLE );

    /* initialize local state */
    CV_INIT_3X3_DELTAS( deltas, step, 1 );
    memcpy( deltas + 8, deltas, 8 * sizeof( deltas[0] ));

    /* initialize writer */
    cvStartAppendToSeq( contour, &writer );

    if( method < 0 )
        ((CvChain *)contour)->origin = pt;

    rect.x = rect.width = pt.x;
    rect.y = rect.height = pt.y;

    s_end = s = CV_IS_SEQ_HOLE( contour ) ? 0 : 4;

    do
    {
        s = (s - 1) & 7;
        i1 = i0 + deltas[s];
        if( (*i1 & value_mask) == ccomp_val )
            break;
    }
    while( s != s_end );

    if( s == s_end )            /* single pixel domain */
    {
        *i0 = nbd1;
        if( method >= 0 )
        {
            CV_WRITE_SEQ_ELEM( pt, writer );
        }
    }
    else
    {
        i3 = i0;