Merge pull request #19859 from danielenricocahall:fix-blob-detector-single-thresh

Fix Single ThresholdBug in Simple Blob Detector

* address bug with using min dist between blobs in blob detector

cast type in comparison and remove docs

address bug with using min dist between blobs in blob detector

use scalar instead of int

address bug with using min dist between blobs in blob detector

* fix namespace and formatting

diff --git a/modules/features2d/src/blobdetector.cpp b/modules/features2d/src/blobdetector.cpp
index d07e8bae83c6aee44cca9cd45e165a0f9e4eb031..c2215cd57c702658481a286856a13e54dc59bec7 100644 (file)
--- a/modules/features2d/src/blobdetector.cpp
+++ b/modules/features2d/src/blobdetector.cpp
@@ -325,13 +325,19 @@ void SimpleBlobDetectorImpl::detect(InputArray image, std::vector<cv::KeyPoint>&
 
         std::vector < Center > curCenters;
         findBlobs(grayscaleImage, binarizedImage, curCenters);
+        if(params.maxThreshold - params.minThreshold <= params.thresholdStep) {
+            // if the difference between min and max threshold is less than the threshold step
+            // we're only going to enter the loop once, so we need to add curCenters
+            // to ensure we still use minDistBetweenBlobs
+            centers.push_back(curCenters);
+        }
         std::vector < std::vector<Center> > newCenters;
         for (size_t i = 0; i < curCenters.size(); i++)
         {
             bool isNew = true;
             for (size_t j = 0; j < centers.size(); j++)
             {
-                double dist = norm(centers[j][ centers[j].size() / 2 ].location - curCenters[i].location);
+                double dist = norm(centers[j][centers[j].size() / 2 ].location - curCenters[i].location);
                 isNew = dist >= params.minDistBetweenBlobs && dist >= centers[j][ centers[j].size() / 2 ].radius && dist >= curCenters[i].radius;
                 if (!isNew)
                 {

diff --git a/modules/features2d/test/test_blobdetector.cpp b/modules/features2d/test/test_blobdetector.cpp
new file mode 100644 (file)
index 0000000..56b7145
--- /dev/null
+++ b/modules/features2d/test/test_blobdetector.cpp
@@ -0,0 +1,21 @@
+// 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 "test_precomp.hpp"
+
+namespace opencv_test { namespace {
+TEST(Features2d_BlobDetector, bug_6667)
+{
+    cv::Mat image = cv::Mat(cv::Size(100, 100), CV_8UC1, cv::Scalar(255, 255, 255));
+    cv::circle(image, Point(50, 50), 20, cv::Scalar(0), -1);
+    SimpleBlobDetector::Params params;
+    params.minThreshold = 250;
+    params.maxThreshold = 260;
+    std::vector<KeyPoint> keypoints;
+
+    Ptr<SimpleBlobDetector> detector = SimpleBlobDetector::create(params);
+    detector->detect(image, keypoints);
+    ASSERT_NE((int) keypoints.size(), 0);
+}
+}} // namespace