cvapprox.cpp.svn-base

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#include "_cv.h"
#include <limits.h>
#include "_cvdatastructs.h"

/****************************************************************************************\
*                                  Chain Approximation                                   *
\****************************************************************************************/

typedef struct _CvPtInfo
{
    CvPoint pt;
    int k;                      /* support region */
    int s;                      /* curvature value */
    struct _CvPtInfo *next;
}
_CvPtInfo;


/* curvature: 0 - 1-curvature, 1 - k-cosine curvature. */
CvStatus
icvApproximateChainTC89( CvChain*               chain,
                         int                    header_size,
                         CvMemStorage*          storage, 
                         CvSeq**                contour, 
                         CvChainApproxMethod    method )
{
    static const int abs_diff[] = { 1, 2, 3, 4, 3, 2, 1, 0, 1, 2, 3, 4, 3, 2, 1 };

    char            local_buffer[1 << 16];
    char*           buffer = local_buffer;
    int             buffer_size;

    _CvPtInfo       temp;
    _CvPtInfo       *array, *first = 0, *current = 0, *prev_current = 0;
    int             i, j, i1, i2, s, len;
    int             count;

    CvChainPtReader reader;
    CvSeqWriter     writer;
    CvPoint         pt = chain->origin;
   
    assert( chain && contour && buffer );

    buffer_size = (chain->total + 8) * sizeof( _CvPtInfo );

    *contour = 0;

    if( !CV_IS_SEQ_CHAIN_CONTOUR( chain ))
        return CV_BADFLAG_ERR;

    if( header_size < (int)sizeof(CvContour) )
        return CV_BADSIZE_ERR;
    
    cvStartWriteSeq( (chain->flags & ~CV_SEQ_ELTYPE_MASK) | CV_SEQ_ELTYPE_POINT,
                     header_size, sizeof( CvPoint ), storage, &writer );
    
    if( chain->total == 0 )
    {        
        CV_WRITE_SEQ_ELEM( pt, writer );
        goto exit_function;
    }

    cvStartReadChainPoints( chain, &reader );

    if( method > CV_CHAIN_APPROX_SIMPLE && buffer_size > (int)sizeof(local_buffer))
    {
        buffer = (char *) icvAlloc( buffer_size );
        if( !buffer )
            return CV_OUTOFMEM_ERR;
    }

    array = (_CvPtInfo *) buffer;
    count = chain->total;

    temp.next = 0;
    current = &temp;

    /* Pass 0.
       Restores all the digital curve points from the chain code.
       Removes the points (from the resultant polygon)
       that have zero 1-curvature */
    for( i = 0; i < count; i++ )
    {
        int s, prev_code = *reader.prev_elem;

        reader.prev_elem = reader.ptr;
        CV_READ_CHAIN_POINT( pt, reader );

        /* calc 1-curvature */
        s = abs_diff[reader.code - prev_code + 7];

        if( method <= CV_CHAIN_APPROX_SIMPLE )
        {
            if( method == CV_CHAIN_APPROX_NONE || s != 0 )
            {
                CV_WRITE_SEQ_ELEM( pt, writer );
            }
        }
        else
        {
            if( s != 0 )
                current = current->next = array + i;
            array[i].s = s;
            array[i].pt = pt;
        }
    }

    //assert( pt.x == chain->origin.x && pt.y == chain->origin.y );

    if( method <= CV_CHAIN_APPROX_SIMPLE )
        goto exit_function;

    current->next = 0;

    len = i;
    current = temp.next;

    assert( current );

    /* Pass 1.
       Determines support region for all the remained points */
    do
    {
        CvPoint pt0;
        int k, l = 0, d_num = 0;

        i = current - array;
        pt0 = array[i].pt;

        /* determine support region */
        for( k = 1;; k++ )
        {
            int lk, dk_num;
            int dx, dy;
            int di;
            float d;

            assert( k <= len );

            /* calc indices */
            i1 = i - k;
            i1 += i1 < 0 ? len : 0;
            i2 = i + k;
            i2 -= i2 >= len ? len : 0;

            dx = array[i2].pt.x - array[i1].pt.x;
            dy = array[i2].pt.y - array[i1].pt.y;

            /* distance between p_(i - k) and p_(i + k) */
            lk = dx * dx + dy * dy;

            /* distance between p_i and the line (p_(i-k), p_(i+k)) */
            dk_num = (pt0.x - array[i1].pt.x) * dy - (pt0.y - array[i1].pt.y) * dx;
            d = (float) (((double) d_num) * lk - ((double) dk_num) * l);
            di = *(int *) &d;

            if( k > 1 && (l >= lk || (d_num > 0 && di <= 0 || d_num < 0 && di >= 0)))
                break;

            d_num = dk_num;
            l = lk;
        }

        current->k = --k;

        /* determine cosine curvature if it should be used */
        if( method == CV_CHAIN_APPROX_TC89_KCOS )
        {
            /* calc k-cosine curvature */
            for( j = k, s = 0; j > 0; j-- )
            {
                double temp_num;
                float temp;
                int sk;
                int dx1, dy1, dx2, dy2;

                i1 = i - j;
                i1 += i1 < 0 ? len : 0;
                i2 = i + j;
                i2 -= i2 >= len ? len : 0;

                dx1 = array[i1].pt.x - pt0.x;
                dy1 = array[i1].pt.y - pt0.y;
                dx2 = array[i2].pt.x - pt0.x;
                dy2 = array[i2].pt.y - pt0.y;

                if( (dx1 | dy1) == 0 || (dx2 | dy2) == 0 )
                    break;

                temp_num = dx1 * dx2 + dy1 * dy2;
                temp_num =
                    (float) (temp_num /
                             sqrt( ((double)dx1 * dx1 + (double)dy1 * dy1) *
                                   ((double)dx2 * dx2 + (double)dy2 * dy2) ));
                temp = (float) (temp_num + 1.1);
                sk = *((int *) &temp);

                assert( 0 <= temp && temp <= 2.2 );
                if( j < k && sk <= s )
                    break;

                s = sk;
            }
            current->s = s;
        }
        current = current->next;
    }
    while( current != 0 );

    prev_current = &temp;
    current = temp.next;

    /* Pass 2.
       Performs non-maxima supression */
    do
    {
        int k2 = current->k >> 1;

        s = current->s;
        i = current - array;

        for( j = 1; j <= k2; j++ )
        {
            i2 = i - j;
            i2 += i2 < 0 ? len : 0;

            if( array[i2].s > s )
                break;

            i2 = i + j;
            i2 -= i2 >= len ? len : 0;

            if( array[i2].s > s )
                break;
        }

        if( j <= k2 )           /* exclude point */
        {
            prev_current->next = current->next;
            current->s = 0;     /* "clear" point */
        }
        else
            prev_current = current;
        current = current->next;
    }
    while( current != 0 );

    /* Pass 3.
       Removes non-dominant points with 1-length support region */
    current = temp.next;
    assert( current );
    prev_current = &temp;

    do
    {
        if( current->k == 1 )
        {
            s = current->s;
            i = current - array;

            i1 = i - 1;
            i1 += i1 < 0 ? len : 0;

            i2 = i + 1;
            i2 -= i2 >= len ? len : 0;

            if( s <= array[i1].s || s <= array[i2].s )
            {
                prev_current->next = current->next;
                current->s = 0;
            }
            else
                prev_current = current;
        }
        else
            prev_current = current;
        current = current->next;
    }
    while( current != 0 );

    if( method == CV_CHAIN_APPROX_TC89_KCOS )
        goto copy_vect;

    /* Pass 4.
       Cleans remained couples of points */
    assert( temp.next );

    if( array[0].s != 0 && array[len - 1].s != 0 )      /* specific case */
    {
        for( i1 = 1; i1 < len && array[i1].s != 0; i1++ )
        {
            array[i1 - 1].s = 0;
        }
        if( i1 == len )
            goto copy_vect;     /* all points survived */
        i1--;

        for( i2 = len - 2; i2 > 0 && array[i2].s != 0; i2-- )
        {
            array[i2].next = 0;
            array[i2 + 1].s = 0;
        }
        i2++;

        if( i1 == 0 && i2 == len - 1 )  /* only two points */
        {
            i1 = array[0].next - array;
            array[len] = array[0];      /* move to the end */
            array[len].next = 0;
            array[len - 1].next = array + len;
        }
        temp.next = array + i1;
    }

    current = temp.next;
    first = prev_current = &temp;
    count = 1;

    /* do last pass */
    do
    {
        if( current->next == 0 || current->next - current != 1 )
        {
            if( count >= 2 )
            {
                if( count == 2 )
                {
                    int s1 = prev_current->s;
                    int s2 = current->s;

                    if( s1 > s2 || s1 == s2 && prev_current->k <= current->k )
                        /* remove second */
                        prev_current->next = current->next;
                    else
                        /* remove first */
                        first->next = current;
                }
                else
                    first->next->next = current;
            }
            first = current;
            count = 1;
        }
        else
            count++;
        prev_current = current;
        current = current->next;
    }
    while( current != 0 );

  copy_vect:

    /* gather points */
    current = temp.next;
    assert( current );

    do
    {
        CvPoint pt = current->pt;

        CV_WRITE_SEQ_ELEM( pt, writer );
        current = current->next;
    }
    while( current != 0 );

exit_function:

    *contour = cvEndWriteSeq( &writer );

    assert( writer.seq->total > 0 );

    if( buffer != local_buffer )
        icvFree( &buffer );
    return CV_OK;
}


/*Applies some approximation algorithm to chain-coded contour(s) and
  converts it/them to polygonal representation */
CV_IMPL CvSeq*
cvApproxChains( CvSeq*              src_seq,
                CvMemStorage*       storage,
                CvChainApproxMethod method,
                double              /*parameter*/, 
                int                 minimal_perimeter, 
                int                 recursive )
{
    CvSeq *prev_contour = 0, *parent = 0;
    CvSeq *dst_seq = 0;
    
    CV_FUNCNAME( "cvApproxChains" );

    __BEGIN__;

    if( !src_seq || !storage )
        CV_ERROR_FROM_STATUS( CV_NULLPTR_ERR );
    if( method > CV_CHAIN_APPROX_TC89_KCOS || method <= 0 || minimal_perimeter < 0 )
        CV_ERROR_FROM_STATUS( CV_BADRANGE_ERR );

    while( src_seq != 0 )
    {
        int len = src_seq->total;

        if( len >= minimal_perimeter )
        {
            CvSeq *contour;
            
            switch( method )
            {