feature-detection | 易学教程

OpenCV ORB detector finds very few keypoints

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问题 I'm trying to use the ORB keypoint detector and it seems to be returning much fewer points than the SIFT detector and the FAST detector. This image shows the keypoints found by the ORB detector: and this image shows the keypoints found by the SIFT detection stage (FAST returns a similar number of points). Having such few points is resulting in very poor feature matching results across images. I'm just curious about the detection stage of ORB right now though because this seems like I'm

OpenCV Python Feature Detection: how to provide a mask? (SIFT)

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I am building a simple project in Python3, using OpenCV3, trying to match jigsaw pieces to the "finished" jigsaw image. I have started my tests by using SIFT. I can extract the contour of the jigsaw piece and crop the image but since most of the high frequencies reside, of course, around the piece (where the piece ends and the floor starts), I want to pass a mask to the SIFT detectAndCompute() method, thus forcing the algorithm to look for the keypoints only within the piece. test_mask = np.ones(img1.shape, np.uint8) kp1, des1 = sift.detectAndCompute(img1, mask = test_mask) After passing a

Advice for algorithm choice

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I have to do a project that tries to scan the shape of the vehicles and detect what type of vehicle it is , the scanning will performed with a sensors called “vehicle scanner” they are just 50 beams of lights, each beam with receptor and emission as it is shown in the picture: I get from the sensors the raw sate of each beam (block or unblock) and with that continuous scanning we can create a probably very low res image of the vehicle. My question is what algorithms/technique I can use to detect and identify the shape of the vehicle, we want to count the wheels, and if we can, try to identify

Feature-detect: mutation-event availability in JavaScript?

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How can my JavaScript detect if an event is available? I'm aware of some great event-compatibility tables , but I need to use feature detection, not browser-sniffing plus a lookup table. Specifically, my JS makes great use of the DOM mutation events ( DOMNodeInserted and DOMSubtreeModified ) -- which work great in all browsers except (of course) Internet Explorer. So, how would I detect if a browser supports DOMNodeInserted ? If you just want to check if the browser supports mutation events in general, you can use this simple test: var hasMutationEvents = ("MutationEvent" in window); Here are

Facial feature detection with OpenCV with eyes and mouth corners points

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问题 I'm working on a face feature detection project and I do detect the eyes, nose and mouth using OpenCv withHaarcascade xml files. But, I want to have the eyes and mouth corners points and the nose center. The goal is using it to predict emotions. I found this link that shows how it works, and I need to get to this result using JAVA. Could any one help me? Thanks in advance. http://cmp.felk.cvut.cz/~uricamic/flandmark/ in this part we receve the face image and we drawRect on the face: public

Detecting small circles with OpenCV (bad image quality)

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问题 I'm trying to detect the four dots you can see in the center of this picture: This one is converted to png, I actually use a ppm format (after conversion from raw output from the camera). The actual processed image is available here I'm new to opencv and therefore have a huge problem detecting those dots. Here's my so far best result: As you can see, I've detected 3 of the dots, but aside from that also lots of other things in the picture are recognized as circles. And here's the code:

How to black out everything outside a circle in Open CV

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问题 I am currently trying to black out everything outside a circle. I am drawing the circle using the following lines of code: cv::Point center(cvRound(circles[i][0]), cvRound(circles[i][1])); // CVRound converts floating numbers to integer int radius = cvRound(circles[i][2]); // Radius is the third parameter [i][0] = x [i][1]= y [i][2] = radius circle( image, center, 3, cv::Scalar(0,255,0), -1, 8, 0 ); // Drawing little circle to Image Center , next Line of Code draws the real circle circle(

OpenCV: howto use mask parameter for feature point detection (SURF)

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问题 I want to limit a SurfFeatureDetector to a set of regions (mask). For a test I define only a single mask: Mat srcImage; //RGB source image Mat mask = Mat::zeros(srcImage.size(), srcImage.type()); Mat roi(mask, cv::Rect(10,10,100,100)); roi = Scalar(255, 255, 255); SurfFeatureDetector detector(); std::vector<KeyPoint> keypoints; detector.detect(srcImage, keypoints, roi); // crash //detector.detect(srcImage, keypoints); // does not crash When I pass the "roi" as the mask I get this error:

Feature detection for position: fixed

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问题 I am trying to find a script that detects if a device places position: fixed elements relative to the ViewPort and not to the entire document. Currently, standard desktop browsers and Mobile Safari (for iOS 5) do so, whereas Android devices place the fixed elements relative to the entire document. I have found a couple of tests to detect this, but none of the seem to work: http://kangax.github.com/cft/ Gives me a false positive when I pass it from an Android device. https://gist.github.com

How to detect if Oracle database supports auto increment?

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I'm working on a project in which we may be using an Oracle 11g or an Oracle 12c database depending on what's available in various environments -- not ideal I know :( My project is a Spring Boot application and I'm using Liquibase to manage the database objects. My problem is that if I'm running on an Oracle 12c database, I'd like to take advantage of auto incrementing IDs while on Oracle 11g, I'll have to rely on a trigger and a sequence. Is there a way to detect if the current version of Oracle supports auto incrementing or do I have to look at the version number? The SQL that I currently