/* calculates length of a curve (e.g. contour perimeter) */
CV_IMPL double
cvArcLength( const void *array, CvSlice slice, int is_closed )
{
double perimeter = 0;
int i, j = 0, count;
const int N = 16;
float buf[N];
CvMat buffer = cvMat( 1, N, CV_32F, buf );
CvSeqReader reader;
CvContour contour_header;
CvSeq* contour = 0;
CvSeqBlock block;
if( CV_IS_SEQ( array ))
{
contour = (CvSeq*)array;
if( !CV_IS_SEQ_POLYLINE( contour ))
CV_Error( CV_StsBadArg, "Unsupported sequence type" );
if( is_closed < 0 )
is_closed = CV_IS_SEQ_CLOSED( contour );
}
else
{
is_closed = is_closed > 0;
contour = cvPointSeqFromMat(
CV_SEQ_KIND_CURVE | (is_closed ? CV_SEQ_FLAG_CLOSED : 0),
array, &contour_header, &block );
}
if( contour->total > 1 )
{
int is_float = CV_SEQ_ELTYPE( contour ) == CV_32FC2;
cvStartReadSeq( contour, &reader, 0 );
cvSetSeqReaderPos( &reader, slice.start_index );
count = cvSliceLength( slice, contour );
count -= !is_closed && count == contour->total;
// scroll the reader by 1 point
reader.prev_elem = reader.ptr;
CV_NEXT_SEQ_ELEM( sizeof(CvPoint), reader );
for( i = 0; i < count; i++ )
{
float dx, dy;
if( !is_float )
{
CvPoint* pt = (CvPoint*)reader.ptr;
CvPoint* prev_pt = (CvPoint*)reader.prev_elem;
dx = (float)pt->x - (float)prev_pt->x;
dy = (float)pt->y - (float)prev_pt->y;
}
else
{
CvPoint2D32f* pt = (CvPoint2D32f*)reader.ptr;
CvPoint2D32f* prev_pt = (CvPoint2D32f*)reader.prev_elem;
dx = pt->x - prev_pt->x;
dy = pt->y - prev_pt->y;
}
reader.prev_elem = reader.ptr;
CV_NEXT_SEQ_ELEM( contour->elem_size, reader );
// Bugfix by Axel at rubico.com 2010-03-22, affects closed slices only
// wraparound not handled by CV_NEXT_SEQ_ELEM
if( is_closed && i == count - 2 )
cvSetSeqReaderPos( &reader, slice.start_index );
buffer.data.fl[j] = dx * dx + dy * dy;
if( ++j == N || i == count - 1 )
{
buffer.cols = j;
cvPow( &buffer, &buffer, 0.5 );
for( ; j > 0; j-- )
perimeter += buffer.data.fl[j-1];
}
}
}
return perimeter;
}
/*
* If curve is closed, return true. Otherwise return false.
*/
VALUE
rb_closed_q(VALUE self)
{
return CV_IS_SEQ_CLOSED(CVSEQ(self)) ? Qtrue : Qfalse;
}
