Object detection with simpleBlobDetector, but it doesn't work - c++

Question

I have a problem with the code for the simpleBlobDetector. I can build and run all the code just fine, but the blobs that the program detects are only the size of a pixel or so. I've already tried to change the param.minArea and maxArea but it doesn't work. So Im asking you guys for help. By the way the image i was using is in grayscale already so it isn't because of my threshold command that it isn't working. Thanks before hand!
Martin.
#include <opencv/cv.h>
#include <opencv/highgui.h>
#include <opencv2/opencv.hpp>
using namespace std;
using namespace cv;
int main(){
Mat src;
Mat dst;
src = imread("C:\\Users\\martin\\Desktop\\ThermalImage2.png", CV_LOAD_IMAGE_GRAYSCALE); //Load an image from directory path
if (! src.data){
cout << "Could not open or find the image" << endl ; // Look for invalid input
return -1;
}
else{
double thresh = 130; // Threshold
double maxValue = 255; // Value assigned to the pixel if it is over 'thresh'
threshold(src, dst, thresh, maxValue, THRESH_BINARY); // threshold the picture src and call it dst
namedWindow("thresholdedPicture", WINDOW_AUTOSIZE); // Create a window
imshow("thresholdedPicture", dst); // display thresholded picture in the window
}
SimpleBlobDetector::Params params; // Set parameters for the object detection
params.minDistBetweenBlobs = 10; //Minimum distance between blobs
params.filterByColor = true;
params.blobColor = 255;
params.filterByArea = true; // filter by area of the blob
params.minArea = 1 ;// Minimum area of the blob
params.maxArea = 100000; // Maximum area of the blob
vector<KeyPoint> keypoints;
cv::SimpleBlobDetector detector(params); // Set up the blob detector with the parameters (params)
detector.detect(dst, keypoints); // Input thresholded picture for detection of the blobs
Mat dst_blob_dect; // New array to store the picture with the blobs detected
drawKeypoints( dst, keypoints, dst_blob_dect, Scalar(0,0,255), DrawMatchesFlags::DRAW_RICH_KEYPOINTS ); //Drawing a red line around the detected objects
namedWindow("keypoints", WINDOW_AUTOSIZE); // Create a window
imshow("keypoints", dst_blob_dect); // Show the picture with the blobs detected in the window "keypoints"
waitKey(0); // Press any key and the main function returns 0
return 0;}

Answer 1

Try this and use different values for params.minDistBetweenBlobs.
#include "stdafx.h"
#include <opencv/cv.h>
#include <opencv/highgui.h>
#include <opencv2/opencv.hpp>
#include <stdio.h>
using namespace std;
using namespace cv;
int main(){
Mat src;
Mat dst;
src = imread("C:\\Users\\sanche8x\\Pictures\\gather.png", CV_LOAD_IMAGE_GRAYSCALE); //Load an image from directory path
if (! src.data){
cout << "Could not open or find the image" << endl ; // Look for invalid input
return -1;
}
else{
double thresh = 130; // Threshold
double maxValue = 255; // Value assigned to the pixel if it is over 'thresh'
threshold(src, dst, thresh, maxValue, THRESH_BINARY); // threshold the picture src and call it dst
namedWindow("thresholdedPicture", WINDOW_AUTOSIZE); // Create a window
imshow("thresholdedPicture", dst); // display thresholded picture in the window
}
SimpleBlobDetector::Params params; // Set parameters for the object detection
params.minDistBetweenBlobs = 10; //Minimum distance between blobs
params.filterByColor = true;
params.blobColor = 255;
params.filterByCircularity = false;
params.filterByConvexity = false;
params.filterByInertia = false;
params.filterByArea = true; // filter by area of the blob
params.minArea = 1 ;// Minimum area of the blob
params.maxArea = 100000; // Maximum area of the blob
vector<KeyPoint> keypoints;
cv::SimpleBlobDetector detector(params); // Set up the blob detector with the parameters (params)
detector.detect(dst, keypoints); // Input thresholded picture for detection of the blobs
Mat dst_blob_dect; // New array to store the picture with the blobs detected
drawKeypoints( dst, keypoints, dst_blob_dect, Scalar(0,0,255), DrawMatchesFlags::DRAW_RICH_KEYPOINTS ); //Drawing a red line around the detected objects
namedWindow("keypoints", WINDOW_AUTOSIZE); // Create a window
imshow("keypoints", dst_blob_dect); // Show the picture with the blobs detected in the window "keypoints"
waitKey(0); // Press any key and the main function returns 0
return 0;
}