connectedComponents: peep-hole optimizations, mostly surrouding the fact that…

connectedComponents: peep-hole optimizations, mostly surrouding the fact that cv::Mat::at is expensive in a tight-loop -also added a "blobstats" version

modules/imgproc/include/opencv2/imgproc/imgproc.hpp

@@ -1091,9 +1091,24 @@ enum { TM_SQDIFF=0, TM_SQDIFF_NORMED=1, TM_CCORR=2, TM_CCORR_NORMED=3, TM_CCOEFF
 CV_EXPORTS_W void matchTemplate( InputArray image, InputArray templ,
                                  OutputArray result, int method );
 
+
+struct CV_EXPORTS ConnectedComponentStats
+{
+    int32_t lower_x;
+    int32_t lower_y;
+    int32_t upper_x;
+    int32_t upper_y;
+    double centroid_x;
+    double centroid_y;
+    uint64_t integral_x;
+    uint64_t integral_y;
+    uint32_t area;
+};
 //! computes the connected components labeled image of boolean image I with 4 or 8 way connectivity - returns N, the total
-//number of labels [0, N-1] where 0 represents the background label.
+//number of labels [0, N-1] where 0 represents the background label. L's value type determines the label type, an important
+//consideration based on the total number of labels or alternatively the total number of pixels.
 CV_EXPORTS_W uint64_t connectedComponents(Mat &L, const Mat &I, int connectivity = 8);
+CV_EXPORTS_W uint64_t connectedComponents(Mat &L, const Mat &I, std::vector<ConnectedComponentStats> &statsv, int connectivity = 8);
 
 
 //! mode of the contour retrieval algorithm

samples/cpp/connected_components.cpp

@@ -12,7 +12,7 @@ static void on_trackbar(int, void*)
 {
     Mat bw = threshval < 128 ? (img < threshval) : (img > threshval);
     Mat labelImage(img.size(), CV_32S);
-    int nLabels = connectedComponents(labelImage, bw, 8);
+    uint64_t nLabels = connectedComponents(labelImage, bw, 8);
     Vec3b colors[nLabels];
     colors[0] = Vec3b(0, 0, 0);//background
     for(int label = 1; label < nLabels; ++label){