cvcontours.cpp

将OpenCV移植到DSP上

      cvEndFindContours( &scanner, &first_contour );
      ...

      -----------------------------------------------------------------

      Second variant is more complex and can be used when someone wants store not
      the retrieved contours but transformed ones. (e.g. approximated with some
      non-default algorithm ).
      
      The scheme can be the as following:

      icvContourScanner scanner;
      CvMemStorage*  contour_storage;
      CvMemStorage*  temp_storage;
      CvSeq*  first_contour;
      CvStatus  result;

      ...

      icvCreateMemStorage( &contour_storage, block_size/0 );
      icvCreateMemStorage( &temp_storage, block_size/0 );

      ...
              
      icvStartFindContours8uC1R
              ( <img_params>, temp_storage,
                header_size, approx_method,
                [retrival_mode],
                &scanner );

      for(;;)
      {
          CvSeq* temp_contour;
          CvSeq* new_contour;
          result = icvFindNextContour( scanner, &temp_contour );

          if( result != CV_OK ) break;

          <approximation_function>( temp_contour, contour_storage,
                                    &new_contour, <parameters...> );

          icvSubstituteContour( scanner, new_contour );
          ...
      }

      if( result < 0 ) goto error_processing;

      cvEndFindContours( &scanner, &first_contour );
      ...

      ----------------------------------------------------------------------------
      Third method to retrieve contours may be applied if contours are irrelevant
      themselves but some characteristics of them are used only.
      The usage is similar to second except slightly different internal loop

      for(;;)
      {
          CvSeq* temp_contour;
          result = icvFindNextContour( &scanner, &temp_contour );

          if( result != CV_OK ) break;

          // calculate some characteristics of temp_contour

          icvSubstituteContour( scanner, 0 );
          ...
      }

      new_storage variable is not needed here. 

      Two notes.
      1. Second and third method can interleave. I.e. it is possible to
         remain contours that satisfy with some criteria and reject others.
         In hierarchic case the resulting tree is the part of original tree with
         some nodes absent. But in the resulting tree the contour1 is a child 
         (may be indirect) of contour2 iff in the original tree the contour1
         is a child (may be indirect) of contour2.
*/
static void
icvEndProcessContour( CvContourScanner scanner )
{
    _CvContourInfo *l_cinfo = scanner->l_cinfo;

    if( l_cinfo )
    {
        if( scanner->subst_flag )
        {
            CvMemStoragePos temp;

            cvSaveMemStoragePos( scanner->storage2, &temp );

            if( temp.top == scanner->backup_pos2.top &&
                temp.free_space == scanner->backup_pos2.free_space )
            {
                cvRestoreMemStoragePos( scanner->storage2, &scanner->backup_pos );
            }
            scanner->subst_flag = 0;
        }

        if( l_cinfo->contour )
        {
            cvInsertNodeIntoTree( l_cinfo->contour, l_cinfo->parent->contour,
                                  &(scanner->frame) );
        }
        scanner->l_cinfo = 0;
    }
}

/* replaces one contour with another */
CV_IMPL void
cvSubstituteContour( CvContourScanner scanner, CvSeq * new_contour )
{
    _CvContourInfo *l_cinfo;

    CV_FUNCNAME( "cvSubstituteContour" );

    __BEGIN__;

    if( !scanner )
        CV_ERROR( CV_StsNullPtr, "" );

    l_cinfo = scanner->l_cinfo;
    if( l_cinfo && l_cinfo->contour && l_cinfo->contour != new_contour )
    {
        l_cinfo->contour = new_contour;
        scanner->subst_flag = 1;
    }

    __END__;
}


/* 
    marks domain border with +/-<constant> and stores the contour into CvSeq.
        method:
            <0  - chain
            ==0 - direct
            >0  - simple approximation
*/
static CvStatus
icvFetchContour( char                   *ptr, 
                 int                    step,
                 CvPoint                pt, 
                 CvSeq*                 contour, 
                 int    _method )
{
    const char      nbd = 2;
    int             deltas[16];
    CvSeqWriter     writer;
    char            *i0 = ptr, *i1, *i3, *i4 = 0;
    int             prev_s = -1, s, s_end;
    int             method = _method - 1;

    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;

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

    do
    {
        s = (s - 1) & 7;
        i1 = i0 + deltas[s];
        if( *i1 != 0 )
            break;
    }
    while( s != s_end );

    if( s == s_end )            /* single pixel domain */
    {
        *i0 = (char) (nbd | -128);
        if( method >= 0 )
        {
            CV_WRITE_SEQ_ELEM( pt, writer );
        }
    }
    else
    {
        i3 = i0;
        prev_s = s ^ 4;

        /* follow border */
        for( ;; )
        {
            s_end = s;

            for( ;; )
            {
                i4 = i3 + deltas[++s];
                if( *i4 != 0 )
                    break;
            }
            s &= 7;

            /* check "right" bound */
            if( (unsigned) (s - 1) < (unsigned) s_end )
            {
                *i3 = (char) (nbd | -128);
            }
            else if( *i3 == 1 )
            {
                *i3 = nbd;
            }

            if( method < 0 )
            {
                char _s = (char) s;

                CV_WRITE_SEQ_ELEM( _s, writer );
            }
            else
            {
                if( s != prev_s || method == 0 )
                {
                    CV_WRITE_SEQ_ELEM( pt, writer );
                    prev_s = s;
                }

                pt.x += icvCodeDeltas[s].x;
                pt.y += icvCodeDeltas[s].y;

            }

            if( i4 == i0 && i3 == i1 )
                break;

            i3 = i4;
            s = (s + 4) & 7;
        }                       /* end of border following loop */
    }

    cvEndWriteSeq( &writer );

    if( _method != CV_CHAIN_CODE )
        cvBoundingRect( contour, 1 );

    assert( writer.seq->total == 0 && writer.seq->first == 0 ||
            writer.seq->total > writer.seq->first->count ||
            (writer.seq->first->prev == writer.seq->first &&
             writer.seq->first->next == writer.seq->first) );

    return CV_OK;
}



/* 
   trace contour until certain point is met.
   returns 1 if met, 0 else.
*/
static int
icvTraceContour( char *ptr, int step, char *stop_ptr, int is_hole )
{
    int deltas[16];
    char *i0 = ptr, *i1, *i3, *i4;
    int s, s_end;

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

    assert( (*i0 & -2) != 0 );

    s_end = s = is_hole ? 0 : 4;

    do
    {
        s = (s - 1) & 7;
        i1 = i0 + deltas[s];
        if( *i1 != 0 )
            break;
    }
    while( s != s_end );

    i3 = i0;

    /* check single pixel domain */
    if( s != s_end )
    {
        /* follow border */
        for( ;; )
        {
            s_end = s;

            for( ;; )
            {
                i4 = i3 + deltas[++s];
                if( *i4 != 0 )
                    break;
            }

            if( i3 == stop_ptr || (i4 == i0 && i3 == i1) )
                break;

            i3 = i4;
            s = (s + 4) & 7;
        }                       /* end of border following loop */
    }
    return i3 == stop_ptr;
}


static CvStatus
icvFetchContourEx( char*                ptr, 
                   int                  step,
                   CvPoint              pt, 
                   CvSeq*               contour,
                   int  _method, 
                   int                  nbd,
                   CvRect*              _rect )
{
    int         deltas[16];
    CvSeqWriter writer;
    char        *i0 = ptr, *i1, *i3, *i4;
    CvRect      rect;
    int         prev_s = -1, s, s_end;
    int         method = _method - 1;

    assert( (unsigned) _method <= CV_CHAIN_APPROX_SIMPLE );
    assert( 1 < nbd && nbd < 128 );

    /* 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 != 0 )
            break;
    }
    while( s != s_end );

    if( s == s_end )            /* single pixel domain */
    {
        *i0 = (char) (nbd | 0x80);
        if( method >= 0 )
        {
            CV_WRITE_SEQ_ELEM( pt, writer );
        }
    }
    else
    {
        i3 = i0;

        prev_s = s ^ 4;

        /* follow border */
        for( ;; )
        {
            s_end = s;

            for( ;; )
            {
                i4 = i3 + deltas[++s];
                if( *i4 != 0 )
                    break;
            }
            s &= 7;

            /* check "right" bound */
            if( (unsigned) (s - 1) < (unsigned) s_end )
            {
                *i3 = (char) (nbd | 0x80);
            }
            else if( *i3 == 1 )
            {
                *i3 = (char) nbd;
            }