// define a trackbar callback
void on_trackbar( int h )
{
int j;
int distStep = dist -> widthStep / 4;
float* currPointer;
cvThreshold( gray, edge,
( float )( edge_thresh ),
( float )( edge_thresh ),
CV_THRESH_BINARY );
//Distance transform
cvDistTransform( edge, dist,
CV_DIST_L2,
CV_DIST_MASK_5,
NULL );
cvConvertScale( dist, dist, 5000.0, 0 );
for( j = 0, currPointer = dist -> imageData; j < dist -> height; j++, currPointer += distStep )
{
cvbSqrt( ( float* )( currPointer ),
( float* )( currPointer ),
dist -> width );
}
cvConvertScale( dist, dist32s, 1.0, 0.5 );
cvAndS( dist32s, cvScalarAll(255), dist32s, 0 );
cvConvertScale( dist32s, dist8u1, 1, 0 );
cvConvertScale( dist32s, dist32s, -1, 0 );
cvAddS( dist32s, cvScalarAll(255), dist32s, 0 );
cvConvertScale( dist32s, dist8u2, 1, 0 );
cvCvtPlaneToPix( dist8u1, dist8u2, dist8u2, 0, dist8u );
show_iplimage( wndname, dist8u );
}
CV_IMPL double cvContourPerimeter( CvSeq *contour, CvSlice slice )
{
double perimeter = 0;
int i, j = 0, count;
const int N = 16;
float buffer[N];
CvSeqReader reader;
CV_FUNCNAME("cvCalcContourPerimeter");
__BEGIN__;
if( !contour )
CV_ERROR_FROM_STATUS( CV_NULLPTR_ERR );
if( !CV_IS_SEQ_POLYLINE( contour ))
CV_ERROR_FROM_STATUS( CV_BADFLAG_ERR );
if( contour->total > 1 )
{
CvPoint pt1, pt2;
cvStartReadSeq( contour, &reader, 0 );
cvSetSeqReaderPos( &reader, slice.startIndex );
count = icvSliceLength( slice, contour );
CV_ADJUST_EDGE_COUNT( count, contour );
/* scroll the reader by 1 point */
CV_READ_EDGE( pt1, pt2, reader );
for( i = 0; i < count; i++ )
{
int dx, dy;
int edge_length;
CV_READ_EDGE( pt1, pt2, reader );
dx = pt2.x - pt1.x;
dy = pt2.y - pt1.y;
edge_length = dx * dx + dy * dy;
buffer[j] = (float)edge_length;
if( ++j == N || i == count - 1 )
{
cvbSqrt( buffer, buffer, j );
for( ; j > 0; j-- )
perimeter += buffer[j-1];
}
}
}
__CLEANUP__
__END__
return perimeter;
}
/* for now this function works bad with singular cases
You can see in the code, that when some troubles with
matrices or some variables occur -
box filled with zero values is returned.
However in general function works fine.
*/
static CvStatus icvFitEllipse_32f( CvSeq* points, CvBox2D* box )
{
CvStatus status = CV_OK;
float u[6];
CvMatr32f D = 0;
float S[36]; /* S = D' * D */
float C[36];
float INVQ[36];
/* transposed eigenvectors */
float INVEIGV[36];
/* auxulary matrices */
float TMP1[36];
float TMP2[36];
int i, index = -1;
float eigenvalues[6];
float a, b, c, d, e, f;
float offx, offy;
float *matr;
int n = points->total;
CvSeqReader reader;
int is_float = CV_SEQ_ELTYPE(points) == CV_32FC2;
CvMat _S, _EIGVECS, _EIGVALS;
/* create matrix D of input points */
D = icvCreateMatrix_32f( 6, n );
offx = offy = 0;
cvStartReadSeq( points, &reader );
/* shift all points to zero */
for( i = 0; i < n; i++ )
{
if( !is_float )
{
offx += (float)((CvPoint*)reader.ptr)->x;
offy += (float)((CvPoint*)reader.ptr)->y;
}
else
{
offx += ((CvPoint2D32f*)reader.ptr)->x;
offy += ((CvPoint2D32f*)reader.ptr)->y;
}
CV_NEXT_SEQ_ELEM( points->elem_size, reader );
}
c = 1.f / n;
offx *= c;
offy *= c;
/* fill matrix rows as (x*x, x*y, y*y, x, y, 1 ) */
matr = D;
for( i = 0; i < n; i++ )
{
float x, y;
if( !is_float )
{
x = (float)((CvPoint*)reader.ptr)->x - offx;
y = (float)((CvPoint*)reader.ptr)->y - offy;
}
else
{
x = ((CvPoint2D32f*)reader.ptr)->x - offx;
y = ((CvPoint2D32f*)reader.ptr)->y - offy;
}
CV_NEXT_SEQ_ELEM( points->elem_size, reader );
matr[0] = x * x;
matr[1] = x * y;
matr[2] = y * y;
matr[3] = x;
matr[4] = y;
matr[5] = 1.f;
matr += 6;
}
/* compute S */
icvMulTransMatrixR_32f( D, 6, n, S );
/* fill matrix C */
icvSetZero_32f( C, 6, 6 );
C[2] = 2.f; //icvSetElement_32f( C, 6, 6, 0, 2, 2.f );
C[7] = -1.f; //icvSetElement_32f( C, 6, 6, 1, 1, -1.f );
C[12] = 2.f; //icvSetElement_32f( C, 6, 6, 2, 0, 2.f );
/* find eigenvalues */
//status1 = icvJacobiEigens_32f( S, INVEIGV, eigenvalues, 6, 0.f );
//assert( status1 == CV_OK );
_S = cvMat( 6, 6, CV_32F, S );
_EIGVECS = cvMat( 6, 6, CV_32F, INVEIGV );
_EIGVALS = cvMat( 6, 1, CV_32F, eigenvalues );
cvEigenVV( &_S, &_EIGVECS, &_EIGVALS, 0 );
//avoid troubles with small negative values
for( i = 0; i < 6; i++ )
eigenvalues[i] = (float)fabs(eigenvalues[i]);
cvbSqrt( eigenvalues, eigenvalues, 6 );
cvbInvSqrt( eigenvalues, eigenvalues, 6 );
for( i = 0; i < 6; i++ )
icvScaleVector_32f( &INVEIGV[i * 6], &INVEIGV[i * 6], 6, eigenvalues[i] );
// INVQ = transp(INVEIGV) * INVEIGV
icvMulTransMatrixR_32f( INVEIGV, 6, 6, INVQ );
/* create matrix INVQ*C*INVQ */
icvMulMatrix_32f( INVQ, 6, 6, C, 6, 6, TMP1 );
icvMulMatrix_32f( TMP1, 6, 6, INVQ, 6, 6, TMP2 );
/* find its eigenvalues and vectors */
//status1 = icvJacobiEigens_32f( TMP2, INVEIGV, eigenvalues, 6, 0.f );
//assert( status1 == CV_OK );
_S = cvMat( 6, 6, CV_32F, TMP2 );
cvEigenVV( &_S, &_EIGVECS, &_EIGVALS, 0 );
/* search for positive eigenvalue */
for( i = 0; i < 3; i++ )
{
if( eigenvalues[i] > 0 )
{
index = i;
break;
}
}
/* only 3 eigenvalues must be not zero
and only one of them must be positive
if it is not true - return zero result
*/
if( index == -1 )
{
box->center.x = box->center.y =
box->size.width = box->size.height =
box->angle = 0.f;
goto error;
}
/* now find truthful eigenvector */
icvTransformVector_32f( INVQ, &INVEIGV[index * 6], u, 6, 6 );
/* extract vector components */
a = u[0];
b = u[1];
c = u[2];
d = u[3];
e = u[4];
f = u[5];
{
/* extract ellipse axes from above values */
/*
1) find center of ellipse
it satisfy equation
| a b/2 | * | x0 | + | d/2 | = |0 |
| b/2 c | | y0 | | e/2 | |0 |
*/
float x0, y0;
float idet = 1.f / (a * c - b * b * 0.25f);
/* we must normalize (a b c d e f ) to fit (4ac-b^2=1) */
float scale = cvSqrt( 0.25f * idet );
if (!scale)
{
box->center.x = box->center.y =
box->size.width = box->size.height =
box->angle = 0.f;
goto error;
}
a *= scale;
b *= scale;
c *= scale;
d *= scale;
e *= scale;
f *= scale;
//x0 = box->center.x = (-d * c * 0.5f + e * b * 0.25f) * 4.f;
//y0 = box->center.y = (-a * e * 0.5f + d * b * 0.25f) * 4.f;
x0 = box->center.x = (-d * c + e * b * 0.5f) * 2.f;
y0 = box->center.y = (-a * e + d * b * 0.5f) * 2.f;
/* offset ellipse to (x0,y0) */
/* new f == F(x0,y0) */
f += a * x0 * x0 + b * x0 * y0 + c * y0 * y0 + d * x0 + e * y0;
if (!f)
{
box->center.x = box->center.y =
box->size.width = box->size.height =
box->angle = 0.f;
goto error;
}
scale = -1.f / f;
/* normalize to f = 1 */
a *= scale;
b *= scale;
c *= scale;
}
/* recover center */
box->center.x += offx;
box->center.y += offy;
/* extract axis of ellipse */
/* one more eigenvalue operation */
TMP1[0] = a;
TMP1[1] = TMP1[2] = b * 0.5f;
TMP1[3] = c;
//status1 = icvJacobiEigens_32f( TMP1, INVEIGV, eigenvalues, 2, 0.f );
//assert( status1 == CV_OK );
_S = cvMat( 2, 2, CV_32F, TMP1 );
_EIGVECS = cvMat( 2, 2, CV_32F, INVEIGV );
_EIGVALS = cvMat( 2, 1, CV_32F, eigenvalues );
cvEigenVV( &_S, &_EIGVECS, &_EIGVALS, 0 );
/* exteract axis length from eigenvectors */
box->size.height = 2 * cvInvSqrt( eigenvalues[0] );
box->size.width = 2 * cvInvSqrt( eigenvalues[1] );
if ( !(box->size.height && box->size.width) )
{
assert(0);
}
/* calc angle */
box->angle = cvFastArctan( INVEIGV[3], INVEIGV[2] );
error:
if( D )
icvDeleteMatrix( D );
return status;
}
