new feature: update ellipse detector using projective invariant pruning

modules/ximgproc/README.md

@@ -16,3 +16,4 @@ Extended Image Processing
 - Pei&Lin Normalization
 - Ridge Detection Filter
 - Binary morphology on run-length encoded images
+- Ellipse Detector

modules/ximgproc/doc/ximgproc.bib

@@ -389,3 +389,14 @@ @article{loke2021accelerated
   year={2021},
   publisher={Springer}
 }
+
+@article{jia2017fast,
+  title={A fast ellipse detector using projective invariant pruning},
+  author={Jia, Qi and Fan, Xin and Luo, Zhongxuan and Song, Lianbo and Qiu, Tie},
+  journal={IEEE Transactions on Image Processing},
+  volume={26},
+  number={8},
+  pages={3665--3679},
+  year={2017},
+  publisher={IEEE}
+}

modules/ximgproc/include/opencv2/ximgproc.hpp

@@ -62,6 +62,7 @@
 #include "ximgproc/edgepreserving_filter.hpp"
 #include "ximgproc/color_match.hpp"
 #include "ximgproc/radon_transform.hpp"
+#include "ximgproc/find_ellipses.hpp"
 
 
 /** @defgroup ximgproc Extended Image Processing

modules/ximgproc/include/opencv2/ximgproc/find_ellipses.hpp

@@ -0,0 +1,38 @@
+// This file is part of OpenCV project.
+// It is subject to the license terms in the LICENSE file found in the top-level directory
+// of this distribution and at http://opencv.org/license.html.
+
+#ifndef __OPENCV_FIND_ELLIPSES_HPP__
+#define __OPENCV_FIND_ELLIPSES_HPP__
+
+#include <opencv2/core.hpp>
+
+namespace cv {
+namespace ximgproc {
+
+//! @addtogroup ximgproc
+//! @{
+
+/**
+@brief Finds ellipses fastly in an image using projective invariant pruning.
+*
+* The function detects ellipses in images using projective invariant pruning.
+* For more details about this implementation, please see
+* [JIA2017FAST]  Jia, Qi et al, (2017).
+* A Fast Ellipse Detector using Projective Invariant Pruning. IEEE Transactions on Image Processing.
+*
+@param image input image, could be gray or color.
+@param ellipses output vector of found ellipses. each vector is encoded as five float $x, y, a, b, radius, score$.
+@param scoreThreshold float, the threshold of ellipse score.
+@param reliabilityThreshold float, the threshold of reliability.
+@param centerDistanceThreshold float, the threshold of center distance.
+*/
+CV_EXPORTS_W void findEllipses(
+    InputArray image, OutputArray ellipses,
+    float scoreThreshold = 0.7f, float reliabilityThreshold = 0.5f,
+    float centerDistanceThreshold = 0.05f
+);
+//! @} ximgproc
+}
+}
+#endif

modules/ximgproc/perf/perf_find_ellipses.cpp

@@ -0,0 +1,27 @@
+// This file is part of OpenCV project.
+// It is subject to the license terms in the LICENSE file found in the top-level directory
+// of this distribution and at http://opencv.org/license.html.
+#include "perf_precomp.hpp"
+
+namespace opencv_test { namespace  {
+
+typedef tuple<Size, MatType, int> FindEllipsesTestParam;
+typedef TestBaseWithParam<FindEllipsesTestParam> FindEllipsesTest;
+
+PERF_TEST_P(FindEllipsesTest, perf, Combine(SZ_TYPICAL, Values(CV_8U), Values(1, 3)))
+{
+    FindEllipsesTestParam params = GetParam();
+    Size sz = get<0>(params);
+    int matType = get<1>(params);
+    int srcCn = get<2>(params);
+
+    Mat src(sz, CV_MAKE_TYPE(matType, srcCn));
+    Mat dst(sz, CV_32FC(6));
+
+    declare.in(src, WARMUP_RNG).out(dst);
+
+    TEST_CYCLE() findEllipses(src, dst, 0.7f, 0.5f, 0.05f);
+
+    SANITY_CHECK_NOTHING();
+}
+}} // namespace

modules/ximgproc/samples/find_ellipses.cpp

@@ -0,0 +1,50 @@
+// This file is part of OpenCV project.
+// It is subject to the license terms in the LICENSE file found in the top-level directory
+// of this distribution and at http://opencv.org/license.html.
+
+#include <iostream>
+#include <opencv2/imgproc.hpp>
+#include <opencv2/imgcodecs.hpp>
+#include <opencv2/ximgproc.hpp>
+#include <opencv2/highgui.hpp>
+
+using namespace cv;
+
+int main() {
+
+    // load image
+    Mat img = imread(samples::findFile("stuff.jpg"), IMREAD_COLOR);
+
+    // check if image is loaded
+    if (img.empty()) {
+        std::cout << "fail to open image" << std::endl;
+        return EXIT_FAILURE;
+    }
+
+    // create output array
+    std::vector<Vec6f> ells;
+
+    // test ellipse detection
+    cv::ximgproc::findEllipses(img, ells, 0.4f, 0.7f, 0.02f);
+
+    // print output
+    for (unsigned i = 0; i < ells.size(); i++) {
+        Vec6f ell = ells[i];
+        std::cout << ell << std::endl;
+        Scalar color(0, 0, 255);
+        // draw ellipse on image
+        ellipse(
+                img,
+                Point(cvRound(ell[0]), cvRound(ell[1])),
+                Size(cvRound(ell[2]), cvRound(ell[3])),
+                ell[5] * 180 / CV_PI, 0.0, 360.0, color, 3
+        );
+    }
+
+    // show image
+    imshow("result", img);
+    waitKey();
+
+    // end
+    return 0;
+}