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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Which way is my yarn oriented?

I have an image processing problem. I have pictures of yarn: The individual strands are partly (but not completely) aligned. I would like to find the predominant direction in which they are aligned. In the center of the example image, this…
Alex I
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OpenCV - Detect hand-drawing shapes

Could OpenCV detect the geometric shapes which is drawn by hand as below? The shape can be a rectangle, triangle, circle, curve, arc,polygon,... I am going to develop an android application which detect these shapes.
Nguyen Minh Binh
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Simple Multi-Blob Detection of a Binary Image?

If there is a given 2d array of an image, where threshold has been done and now is in binary information. Is there any particular way to process this image to that I get multiple blob's coordinates on the image? I can't use openCV because this…
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Setting parameters for BRISK in OpenCV

I'm trying to use BRISK implementation of OpenCV (for C++) in order to check in a photo if an image (or a part of an image) is included in. For example, I take a photo, and I try to match it with a set of images in database, and I would like to…
user2180398
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detecting blurred rectangles on multimodal grayscaleimage

I have the following image I'm trying to find the pixel coordinates of main rectangles (those between white lines). I tried few things but I can't obtain good enough solution. The solution doesn't have to be perfect and it's ok if not all…
pzo
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Detecting small circles with OpenCV (bad image quality)

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…
Wojtek
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HOG descriptor for object detection

I would like to know, if there is any implementation for HOG descriptor for objects like "cars" and NOT for Human in MATLAB? But in case, there is only for Human, can you guide me to that code, and give me so HINTS in order to improve the code to be…
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How to use Mikolajczyk's evaluation framework for feature detectors/descriptors?

I'm trying the assess the correctness of my SURF descriptor implementation with the de facto standard framework by Mikolajczyk et. al. I'm using OpenCV to detect and describe SURF features, and use the same feature positions as input to my…
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Affine-SIFT(ASIFT) Feature Detector

I am working on a project where I have to detect the features of an object (in a Video Frame) and match it with other objects (inside some other frame) to recognize the same object for tracking. I have googled many Feature detector algorithms. I…
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Difference between feature detection and object detection

I know that most common object detection involves Haar cascades and that there are many techniques for feature detection such as SIFT, SURF, STAR, ORB, etc... but if my end goal is to recognizes objects doesn't both ways end up giving me the same…
mugetsu
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Detecting outliers in SURF or SIFT algorithm with OpenCV

Which method is the best to compare two images and discard outliers points? In find_obj.cpp opencv example, they use FLANN, but don't discard outliers. I have seen some methods like using Kmeans or graphs.
Wiliam
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Non-maximum suppression in OpenCV

I applied a harris corner detection using openCV which gave me a response map for the potential corners. The documentation states that corners can be found as the local maxima of this response map - does anyone know how this can be done? Thank you.
Chris Arriola
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How to call LSD (LineSegmentDetector) from a c language program?

i'm using LSD to detect straight lines in an image, the code that i have downloaded contains a Minimal example of calling LSD but it's static (i.e it outputs only the value in the main function) i want to apply the code on a video, that's the…
Eslam Hamdy
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Detecting HTML5 data attribute in Modernizr

How do I detect if the browser supports HTML5 data attribute using Modernizr?
Diogo Cardoso
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Implementing Vocabulary Tree in OpenCV

I am trying to implement image search based on paper "Scalable Recognition with a Vocabulary Tree". I am using SURF for extracting the features and key points. For example, for an image i'm getting say 300 key points and each key point has 128…