Questions tagged [feature-detection]

Feature detection is a process in computer vision that aims to find visual features within the image with particular desirable properties. Detected features can be points, image regions or continuous curves in the image. Interesting properties can include invariance to noise, perspective transformations, or properties interesting for specific usages (e.g. tracking).

Feature detection is a process in computer vision that aims to find visual features within the image with particular desirable properties.

Detected features are some subsection of the image, and can be:

  • points (e.g. Harris corners)
  • connected image regions (e.g. DoG or MSER regions)
  • continuous curves in the image

Interesting properties can include invariance to noise, perspective transformations and viewpoint changes (camera translation and rotation), scaling (for use in visual feature matching), or properties interesting for specific usages (e.g. visual tracking).

Important information about visual features can include:

  • coordinates in the image
  • radius of the visual feature
  • scale (octave) of the image on which the feature has been extracted

After detecting the feature with some feature detection algorithm, it is usually described by a descriptor vector (several known descriptors are used today) for the purposes of visual feature matching, while the feature's position in the image can be used directly for application in tracking.

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How to extract number from a detected image

I want to use opencv for extracting a number written of a speed sign. and since the detected sign will be just an image, how can i extract the number written on it? how can I do that using opencv. note: I know how to make image matching, but i do…
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how to detect computer vision blob of pixels within specific color range, using Matlab?

What Matlab computer vision functions will detect, in a single video frame, a blob that is (mostly) of pixels all within a specific color range? I want to detect stationary objects, and am looking for a non-movement function that can detect blobs…
Doug Null
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Detect valid area of a target

Im building a DIY laser target. So far on the software side I managed to find when is a laser shot at the target by calculating differences and threshold, and then find where did it hit in relation to the whole image. Now the next problem I am…
SOMN
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Opencv 3.0 FAST Corner Detection

I am beginner in OpenCV. I have problem implement FAST algoritmus in Vsual Studio with version OpenCV 3.0. I have tried following implementation in c++: src = imread("../images/right.jpg", CV_LOAD_IMAGE_GRAYSCALE); Ptr detector…
Marosko89
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OpenCV Segmentation Fault during Feature Matching

This function extracts and computes the query.keypoints: // extract features analyzer->analyze(query); like this: bool Analyzer::analyze(Query &query) { // detect keypoints query.keypoints.clear(); assert(query.keypoints.empty()); …
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How to track a football's position?

I'm starting to look into tracking a football (soccer ball in the US) and I could use some advice on what approach would be the more reliable and efficient. The ball needs to tacked to determine if it goes between goal posts or not and roughly which…
George Profenza
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How can we use both Hamming distance and distance between coordinates to match features?

As known, for tracking objects in OpenCV we can use: FeatureDetector to find features DescriptorMatcher to match similarity between features of the desired object and features of current frame in video and then use findHomography to find the new…
Alex
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Transition histogram for hand written character image recognition

How to find transition histogram for following image (B is the image histogram shown on bottom and right side of it)? I tried to plot number of black color pixels in each scan line against opposing axis but its not look like the one i needed (in…
Sanjana
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cvFindHomography throws an error

i am using opencv java library and i am doing some image matching and object detection by computing the homography matrix and the perspecive transformation. at run time i the system crash and i rceive the below posted error message and i do not know…
Amrmsmb
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Why I am getting matches despite the object does not exist in the scene

I a trying to make features matching using SIFT algorithm. as shown in figure 1 below, there are matched features betwee the object/query and the scene/train, and i receive the number of good matches equals 8 i repeated the same matching procedure…
Amrmsmb
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How to detect if the image contains the given object or area or these two images are the same in OpenCV

I want to check if the image contains the given part (a small image in side it) or these two image are the same. For better understanding my question look to image bellow. The image which I am looking for inside another images: Some other…
Bahramdun Adil
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open cv Feature matching using given coordinates

I am feature matching between stereo images using openCv, FAST feature detection and Brute force matching. FastFeatureDetector detector(threshold); detector.detect(img1, keypoints1); detector.detect(img2,…
anti
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pre-processing to improve feature detector before tracking - Matlab

I am trying to make tracking for soccer player, I need to detect features from this player and then estimate the distance difference of these pixels over number of frames. first I have to detect the main features of the player and then match them to…
user1217585
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Count total number of studied vocabularies in papers [Image Processing]

I'm doing a DIP project. I want to count the total number of words in each paper using Image Processing. The original image is: I did some pre-processing and produced the image below: My idea to count the total number of words in each paper is to…
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Is there an algorithm to describe a portrait of a person in words?

I'm looking an algorithm that analyzes a portrait-photo of a person and outputs a descriptive text like "young man, rather long nose, green eyes". It doesn't matter if the output is very precise or not; it is for an art installation. But it should…