potok/opencv
1
0
Fork 0
mirror of https://github.com/opencv/opencv.git synced 2026-07-31 00:03:03 +04:00
Code Packages Releases Wiki Activity

Merge pull request #28628 from GideokKim:fix/fitellipse-det-threshold

Browse Source 
imgproc: fix fitEllipseDirect/AMS determinant threshold for near-circular data
This commit is contained in:
Alexander Smorkalov
2026-04-22 10:47:13 +03:00
committed by GitHub
parent 65e9cb43d4 4ebaf2dbb4
commit 1e61a2283d
3 changed files with 64 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files
modules/imgproc/src/shapedescr.cpp
+22 -10
View File
@@ -579,7 +579,9 @@ cv::RotatedRect cv::fitEllipseAMS( InputArray _points )
M(4,3)=DM(3,4);
M(4,4)=DM(4,4);
if (fabs(cv::determinant(M)) > 1.0e-10) {
double npow = (double)n * (double)n;
npow = npow * npow * (double)n; // n^5
if (fabs(cv::determinant(M)) > 1.0e-10 / npow) {
break;
}
@@ -703,6 +705,8 @@ cv::RotatedRect cv::fitEllipseDirect( InputArray _points )
Matx<double, 3, 1> pVec;
double x0, y0, a, b, theta, Ts;
Mat eVal, eVec;
double cond[3];
double s = 0;
for( i = 0; i < n; i++ )
@@ -763,6 +767,11 @@ cv::RotatedRect cv::fitEllipseDirect( InputArray _points )
Ts=(-(DM(3,5)*DM(4,4)*DM(5,3)) + DM(3,4)*DM(4,5)*DM(5,3) + DM(3,5)*DM(4,3)*DM(5,4) - \
DM(3,3)*DM(4,5)*DM(5,4) - DM(3,4)*DM(4,3)*DM(5,5) + DM(3,3)*DM(4,4)*DM(5,5));
if (fabs(Ts) < DBL_EPSILON) {
eps = (float)(s/(n*2)*1e-2);
continue;
}
M(0,0) = (DM(2,0) + (DM(2,3)*TM(0,0) + DM(2,4)*TM(1,0) + DM(2,5)*TM(2,0))/Ts)/2.;
M(0,1) = (DM(2,1) + (DM(2,3)*TM(0,1) + DM(2,4)*TM(1,1) + DM(2,5)*TM(2,1))/Ts)/2.;
M(0,2) = (DM(2,2) + (DM(2,3)*TM(0,2) + DM(2,4)*TM(1,2) + DM(2,5)*TM(2,2))/Ts)/2.;
@@ -773,18 +782,9 @@ cv::RotatedRect cv::fitEllipseDirect( InputArray _points )
M(2,1) = (DM(0,1) + (DM(0,3)*TM(0,1) + DM(0,4)*TM(1,1) + DM(0,5)*TM(2,1))/Ts)/2.;
M(2,2) = (DM(0,2) + (DM(0,3)*TM(0,2) + DM(0,4)*TM(1,2) + DM(0,5)*TM(2,2))/Ts)/2.;
double det = cv::determinant(M);
if (fabs(det) > 1.0e-10)
break;
eps = (float)(s/(n*2)*1e-2);
}
if( iter < 2 ) {
Mat eVal, eVec;
eigenNonSymmetric(M, eVal, eVec);
// Select the eigen vector {a,b,c} which satisfies 4ac-b^2 > 0
double cond[3];
cond[0]=(4.0 * eVec.at<double>(0,0) * eVec.at<double>(0,2) - eVec.at<double>(0,1) * eVec.at<double>(0,1));
cond[1]=(4.0 * eVec.at<double>(1,0) * eVec.at<double>(1,2) - eVec.at<double>(1,1) * eVec.at<double>(1,1));
cond[2]=(4.0 * eVec.at<double>(2,0) * eVec.at<double>(2,2) - eVec.at<double>(2,1) * eVec.at<double>(2,1));
@@ -793,6 +793,18 @@ cv::RotatedRect cv::fitEllipseDirect( InputArray _points )
} else {
i = (cond[0]<cond[2]) ? 2 : 0;
}
// Check that the ellipse condition 4ac-b^2 is meaningfully positive
// (not just positive due to floating-point noise from complex eigenvalues)
{
double v0 = eVec.at<double>(i,0), v1 = eVec.at<double>(i,1), v2 = eVec.at<double>(i,2);
double vnorm2 = v0*v0 + v1*v1 + v2*v2;
if (cond[i] > 1e-6 * vnorm2)
break;
}
eps = (float)(s/(n*2)*1e-2);
}
if( iter < 2 ) {
double norm = std::sqrt(eVec.at<double>(i,0)*eVec.at<double>(i,0) + eVec.at<double>(i,1)*eVec.at<double>(i,1) + eVec.at<double>(i,2)*eVec.at<double>(i,2));
if (((eVec.at<double>(i,0)<0.0 ? -1 : 1) * (eVec.at<double>(i,1)<0.0 ? -1 : 1) * (eVec.at<double>(i,2)<0.0 ? -1 : 1)) <= 0.0) {
norm=-1.0*norm;
modules/imgproc/test/test_fitellipse_ams.cpp
+20
View File
@@ -337,6 +337,26 @@ TEST(Imgproc_FitEllipseAMS_Issue_7, accuracy) {
EXPECT_TRUE(checkEllipse(ellipseAMSTest, ellipseAMSTrue, tol));
}
TEST(Imgproc_FitEllipseAMS_NearCircular, accuracy)
{
std::vector<cv::Point2f> points;
double cx = 27.0, cy = 27.0, a = 17.0, b = 16.5;
for (int i = 0; i < 360; i++) {
double theta = 2.0 * CV_PI * i / 360.0;
points.push_back(cv::Point2f(
(float)(cx + a * cos(theta)),
(float)(cy + b * sin(theta))));
}
cv::RotatedRect ams = cv::fitEllipseAMS(points);
// AMS should produce a valid result close to ground truth
EXPECT_NEAR(ams.center.x, 27.0, 0.5);
EXPECT_NEAR(ams.center.y, 27.0, 0.5);
EXPECT_NEAR(std::max(ams.size.width, ams.size.height), 34.0, 1.0);
EXPECT_NEAR(std::min(ams.size.width, ams.size.height), 33.0, 1.0);
}
TEST(Imgproc_FitEllipseAMS_HorizontalLine, accuracy) {
vector<Point2f> pts({{-300, 100}, {-200, 100}, {-100, 100}, {0, 100}, {100, 100}, {200, 100}, {300, 100}});
const RotatedRect el = fitEllipseAMS(pts);
modules/imgproc/test/test_fitellipse_direct.cpp
+22
View File
@@ -337,6 +337,28 @@ TEST(Imgproc_FitEllipseDirect_Issue_7, accuracy) {
EXPECT_TRUE(checkEllipse(ellipseDirectTest, ellipseDirectTrue, tol));
}
TEST(Imgproc_FitEllipseDirect_NearCircular, accuracy)
{
// 360 points on a near-circular ellipse (a=17, b=16.5)
// This data previously triggered unnecessary fallback to fitEllipseNoDirect
std::vector<cv::Point2f> points;
double cx = 27.0, cy = 27.0, a = 17.0, b = 16.5;
for (int i = 0; i < 360; i++) {
double theta = 2.0 * CV_PI * i / 360.0;
points.push_back(cv::Point2f(
(float)(cx + a * cos(theta)),
(float)(cy + b * sin(theta))));
}
cv::RotatedRect direct = cv::fitEllipseDirect(points);
// Direct should produce a valid result close to ground truth
EXPECT_NEAR(direct.center.x, 27.0, 0.1);
EXPECT_NEAR(direct.center.y, 27.0, 0.1);
EXPECT_NEAR(std::max(direct.size.width, direct.size.height), 34.0, 0.5);
EXPECT_NEAR(std::min(direct.size.width, direct.size.height), 33.0, 0.5);
}
TEST(Imgproc_FitEllipseDirect_HorizontalLine, accuracy) {
vector<Point2f> pts({{-300, 100}, {-200, 100}, {-100, 100}, {0, 100}, {100, 100}, {200, 100}, {300, 100}});
const RotatedRect el = fitEllipseDirect(pts);