keypoint

I followed a blob detection example (using cv2.SimpleBlobDetector ) and successfully detected the blobs in my binary image. But then I don't know how to extract the coordinates and area of the keypoints. Here are the code for the blob detections: # I skipped the parameter setting part. blobParams = cv2.SimpleBlobDetector_Params() blobVer = (cv2.__version__).split('.') if int(blobVer[0]) < 3: detector = cv2.SimpleBlobDetector(blobParams) else: detector = cv2.SimpleBlobDetector_create(blobParams) # Detect Blobs keypoints_black = detector.detect(255-black_blob) trans_blobs = cv2.drawKeypoints

I am trying to understand how to get the descriptor for a given KeyPoint in OpenCV. So far my code looks like follows: #include <iostream> #include "opencv2/opencv.hpp" typedef cv::Mat Image; int main(int argc, const char * argv[]) { Image imgA = cv::imread("images/buddhamulticam_total100.png", CV_LOAD_IMAGE_GRAYSCALE); Image imgB = cv::imread("images/buddhamulticam_total101.png", CV_LOAD_IMAGE_GRAYSCALE); cv::Ptr<cv::FeatureDetector> detector = cv::FeatureDetector::create("ORB"); cv::Ptr<cv::DescriptorExtractor> descriptor = cv::DescriptorExtractor::create("ORB"); std::vector<cv::KeyPoint>

I have a very strange problem. I'm using this code to detect an image in another one (java opencv): UPDATED CODE: public void startRecognition() { //load images, I want to find img_object in img_scene Mat img_scene = Highgui.imread("D:/opencvws/ImageRecognition/src/main/resources/ascene.jpg"); Mat img_object = Highgui.imread("D:/opencvws/ImageRecognition/src/main/resources/aobj1.jpg"); run++; System.out.println("RUN NO: " + run); //init detector FeatureDetector detector = FeatureDetector.create(FeatureDetector.SURF); //keypoint detection for both images (keyponts_scene for img_scene, keypoint

When using OpenCV for example, algorithms like SIFT or SURF are often used to detect keypoints. My question is what actually are these keypoints? I understand that they are some kind of "points of interest" in an image. I also know that they are scale invariant and are circular. Also, I found out that they have orientation but I couldn't understand what this actually is. Is it an angle but between the radius and something? Can you give some explanation? I think I need what I need first is something simpler and after that it will be easier to understand the papers. Those are some very good