Count number of colored objects in image

edit

****** EDIT-2 *******

Based on the comment from Tetragramm, I have simplified the connect_components function. However, I am still getting the same exception:

3, 0
8UC3
OpenCV Error: Assertion failed (L.channels() == 1 && I.channels() == 1) in connectedComponents_sub1, file /source/opencv-3.0.0/modules/imgproc/src/connectedcomponents.cpp, line 341
Exception caught
/source/opencv-3.0.0/modules/imgproc/src/connectedcomponents.cpp:341: error: (-215) L.channels() == 1 && I.channels() == 1 in function connectedComponents_sub1

Maybe I shouldn't use the connectedComponenets function and go at it by the old way (which I'm not sure how to do, so an example would be great!)?

****** EDIT-1 *******

Sorry for the delayed response. Being new to OpenCV I did some research and found out that a connected components function was introduced in OpenCV 3.0 and it is only available in C++ (AFAIK) as shown here. So, I decided to to write my code in C++. I have also updated the test image (I would like to make it work on this before I got to video stream). Here is my code:

#include <iostream>
#include <vector>

#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>

using namespace std;   


cv::Mat connect_components(cv::Mat img, int threshval)
{
    cv::Mat bw = threshval < 128 ? (img < threshval) : (img > threshval);
    cv::Mat labelImage(img.size(), CV_16U);
    auto nLabels = cv::connectedComponents(bw, labelImage, 8);
    bw = labelImage >= 1;
    cv::Mat bwArray[3] = {bw, bw, bw};
    cv::Mat dst(img.size(), CV_8UC3);
    cv::merge(bwArray, 3, dst);
    return dst;
}

int main(int argc, char **argv)
{
    cv::VideoCapture webcam(0);

    if (!webcam.isOpened()) {
        cerr << "Cannot open webcam" << endl;
        exit(-1);
    }

    // Define range for blue and red color in HSV
    const cv::Scalar blue_range[] = { {110, 50, 50}, {130, 255, 255} };
    const cv::Scalar red_range[] = { {0, 200, 50}, {10, 255, 150} };

    cout << CV_MAJOR_VERSION << ", " << CV_MINOR_VERSION << endl;

    cv::Mat original_frame, color_mask[2], final_mask;
    while (true) {
        try {
            webcam.read(original_frame); // grab each frame
            cv::Mat frame_hsv;
            cv::cvtColor(original_frame, frame_hsv, CV_BGR2HSV); // convert BGR to HSV

            // threshold HSV image to get only defined range colors
            cv::inRange(frame_hsv, blue_range[0], blue_range[1], color_mask[0]); 
            cv::inRange(frame_hsv, red_range[0], red_range[1], color_mask[1]);

            // add the masks
            final_mask = color_mask[0] + color_mask[1];

            // Bitwise-AND full mask and original image
            cv::Mat colored_boxes;
            cv::bitwise_and(original_frame, original_frame, colored_boxes, final_mask);

            // Apply morphological closing
            cv::Mat morphed_boxes;
            cv::morphologyEx(colored_boxes, morphed_boxes, cv::MORPH_CLOSE, cv::Mat::ones(10, 10, CV_8UC1));

            // Connected componenets
            auto labeled_boxes = connect_components(colored_boxes, 62);

            // Display the image
            //cv::imshow("Webcam", original_frame);
            cv::imshow("Boxes", morphed_boxes);

            // quit progrem is user inputs ESC or q
            auto user_input = (cv::waitKey(5) & 0xFF);
            if ((user_input == 27) || (user_input == 113)) {
                break;
            }
        }
        catch (cv::Exception &e) {
            cout << "Exception caught" << endl;
            cout << e.what();
            break;
        }
    }

    return 0;
}

The connected_components function is adopted from here. When I run this, I get the following exception:

3, 0
8UC3
OpenCV Error: Assertion failed (L.channels() == 1 && I.channels() == 1) in connectedComponents_sub1, file /source/opencv-3.0.0/modules/imgproc/src/connectedcomponents.cpp, line 341
Exception caught
/source/opencv-3.0.0/modules/imgproc/src/connectedcomponents.cpp ...