Improve fitEllipseDirect tests #27717
### Pull Request Readiness Checklist
Previous `fit_and_check_ellipse` implementation was very weak - it only checks that points center lies inside ellipse.
Current implementation `fit_and_check_ellipse` checks that points RMS (Root Mean Square) algebraic distance is quite small. It means that on average points are near boundary of ellipse. Because for points on ellipse algebraic distance is equal to `0` and for points that are close to boundary of ellipse is quite small
See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request
- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [ ] There is a reference to the original bug report and related work
- [ ] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
Patch to opencv_extra has the same branch name.
- [ ] The feature is well documented and sample code can be built with the project CMake
Fix checking that point lies inside ellipse #27704
### Pull Request Readiness Checklist
Previous `check_pt_in_ellipse` implementation was incorrect. For points on ellipse `cv::norm(to_pt)` should be equal to `el_dist`.
I tested current implementation with following Python script:
```
import cv2
import numpy as np
import matplotlib.pyplot as plt
from matplotlib.patches import Ellipse
def check_pt_in_ellipse(pt, el):
center, axes, angle = ellipse
to_pt = pt - center
el_angle = angle * np.pi / 180
to_pt_r_x = to_pt[0] * np.cos(-el_angle) - to_pt[1] * np.sin(-el_angle)
to_pt_r_y = to_pt[0] * np.sin(-el_angle) + to_pt[1] * np.cos(-el_angle)
pt_angle = np.arctan2(to_pt_r_y / axes[1], to_pt_r_x / axes[0])
x_dist = 0.5 * axes[0] * np.cos(pt_angle)
y_dist = 0.5 * axes[1] * np.sin(pt_angle)
el_dist = np.sqrt(x_dist * x_dist + y_dist * y_dist)
assert abs(np.linalg.norm(to_pt) - el_dist) < 1e-10
# TEST(Imgproc_FitEllipse_Issue_4515, accuracy) {
points = np.array([
[327, 317],
[328, 316],
[329, 315],
[330, 314],
[331, 314],
[332, 314],
[333, 315],
[333, 316],
[333, 317],
[333, 318],
[333, 319],
[333, 320],
])
ellipse = cv2.fitEllipseDirect(points)
center, axes, angle = ellipse
angle_rad = np.deg2rad(angle)
points_on_ellipse = []
for point_angle_deg in range(0, 360, 10):
point_angle = np.deg2rad(point_angle_deg)
point = np.array([0., 0.])
point_x = axes[0] * 0.5 * np.cos(point_angle)
point_y = axes[1] * 0.5 * np.sin(point_angle)
point[0] = point_x * np.cos(angle_rad) - point_y * np.sin(angle_rad)
point[1] = point_x * np.sin(angle_rad) + point_y * np.cos(angle_rad)
point[0] += center[0]
point[1] += center[1]
points_on_ellipse.append(point)
points_on_ellipse = np.array(points_on_ellipse)
for point in points_on_ellipse:
check_pt_in_ellipse(point, ellipse)
plt.figure(figsize=(8, 8))
plt.scatter(points[:, 0], points[:, 1], c='red', label='points')
plt.scatter(points_on_ellipse[:, 0], points_on_ellipse[:, 1], c='yellow', label='ellipse')
ellipse = Ellipse(xy=center, width=axes[0], height=axes[1],
angle=angle, facecolor='none', edgecolor='b')
plt.gca().add_patch(ellipse)
plt.gca().set_aspect('equal')
plt.legend()
plt.show()
```
See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request
- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [ ] There is a reference to the original bug report and related work
- [ ] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
Patch to opencv_extra has the same branch name.
- [ ] The feature is well documented and sample code can be built with the project CMake
Improve robustness for ellipse fitting #26773
### Pull Request Readiness Checklist
Related to #26694
Current noise addition is not very good because for example it turns degenerate case of one horizontal line into degenerate case of two parallel horizontal lines
Improving noise addition leads to improved robustness of algorithms
See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request
- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
Patch to opencv_extra has the same branch name.
- [x] The feature is well documented and sample code can be built with the project CMake
* improved fitEllipse and fitEllipseDirect accuracy in singular or close-to-singular cases (see issue #9923)
* scale points using double precision
* added normalization to fitEllipseAMS as well; fixed Java test case by raising the tolerance (it's unclear what is the correct result in this case).
* improved point perturbation a bit. make the code a little bit more clear
* trying to fix Java fitEllipseTest by slightly raising the tolerance threshold
* synchronized C++ version of Java's fitEllipse test
* removed trailing whitespaces
- removed tr1 usage (dropped in C++17)
- moved includes of vector/map/iostream/limits into ts.hpp
- require opencv_test + anonymous namespace (added compile check)
- fixed norm() usage (must be from cvtest::norm for checks) and other conflict functions
- added missing license headers
MaximSmolskiy
s-trinh
Vadim Pisarevsky
Alexander Alekhin
Rostislav Vasilikhin
arybnikov