Questions tagged [local-features]

The tag has no usage guidance.

80 questions
Filter by
Sorted by
Tagged with
3k views

What Kind of Features Can I Extract from a Signal

I want to monitor (automatic-)gearbox failures on some vehicles. For each vehicle I have a captured signal representing the selected gear at each one millisecond. An example of two signals are shown ...
7k views

normalized Laplacian of Gaussian

Laplacian of Gaussian formula for 2d case is $$\operatorname{LoG}(x,y) = \frac{1}{\pi\sigma^4}\left(\frac{x^2+y^2}{2\sigma^2} - 1\right)e^{-\frac{x^2+y^2}{2\sigma^2}},$$ in scale-space related ...
300 views

Haralick features, am I approaching this correctly?

I'm trying to personalise a custom CBIR by adding more features not only based on colour, but based on textures' features. What I don't know is if I'm approaching this well with Haralick's features. ...
56 views

Corner detector vs feature detector

In the literature, I see "corner detector" and "feature detector" are interchangeably used for these methods e.g. Harris, Shi-Tomasi, FAST, etc. What is the difference between a ...
44 views

Invariances of FFT-based Image-Registration vs. SIFT-Features

TL;DR: I don't understand how invariant FFT-based image-registration techniques are to object alterations (scratches, marks etc.) in comparison to SIFT-features. I want to build kind of a feature-...
19k views

How Hessian feature detector works?

I know about Harris corner detector, and I understand the basic idea of its second moment matrix, $$M = \left[ \begin{array}{cc} I_x^2 & I_xI_y \\ I_xI_y & I_y^2 \end{array} \right]$$, edges ...
25 views

Are location in BRIEF feature descriptor reused?

In the BRIEF feature descriptor ("BRIEF: Binary Robust IndependentElementary Features", Calonder et al., 2011) they investigate five different methods of choosing point pairs to compute the ...
175 views

What Is an Oriented Gaussian Second Derivative Filter

In the paper: Detecting and Localizing Edges Composed of Steps, Peaks and Roofs, the authors refer to an image filter as an oriented second-derivative Gaussian filter. I'm trying to figure out what ...
18k views

What is the difference between feature detectors and feature descriptors?

What is the difference between feature detectors and feature descriptors? Which among these are detectors and which are descriptors: Harris, SURF, Min Eigen, FAST, SIFT, BRISK
5k views

Principal Component Analysis (PCA) on Convolutional Neural Network (CNN) Features

Please, I have a question regarding PCA and features which are extracted from a convolutional layer. link if we have a test dataset , and we extract all conv features of all images at test dataset ...
100 views

Use sparse optical tracking to track a Bounding Box object

I need some help on solving this issue. Any tips are appreciated. The goal of the project is to try to track a Bounding Box object, chosen arbitrarily in an image, throughout many frames of a ...
361 views

Sum of Squared Intensity Difference for block matching with ORB features, c++

I am trying to implement feature matching algorithm between image reference and image current. The pipeline is as follows: ...
14k views

Feature extraction/reduction using DWT

For a given time series which is n timestamps in length, we can take Discrete Wavelet Transform (using 'Haar' wavelets), then we get (for an example, in Python) - ...
29 views

What are the ranges of values for each audio feature/descriptor?

I need to normalize some audio feature measurements I've done with the software Wolfram Mathematica. Coming from a non signal processing background, I have some difficulties understanding what ...
291 views

I am learning about HOG and I understand it from here. A well-explained page with an example. I am not understanding this concept that how it works A 16×16 block has 4 histograms which can be ...
57 views

Finding Local mean value of pixels of window

I want to solve the equation (2) in the attached picture which tells the local mean value. But i don't have any idea about how to evaluate this equation using matlab code. could only guess w indicates ...
560 views

How can I extract information about timbre from a .wav file. In which form can I study those features?

To study the frequencies of a piece of audio, we can generate a spectrogram from that audio file. I'm wondering how the features of timbre are saved in such tiny wave files, and how we can extract ...
19k views

Scale and Rotation invariant feature descriptors

Can you list some scale and rotational invariant feature descriptors for use in feature detection. The application is for the detection of cars and humans in video captured by a UAV, using a multi-...
1k views

105 views

What makes an image feature stable?

Feature detection is an essential task in low-level vision. Good features are those that resist to different perturbations such as noise addition, blur, geometric transforms (3D rotation with ...
63 views

How to recognise different symbols from their slope ? like (<,>,^) etc

i am trying to build a program in which user input a symbol with mouse and program recognise the symbol by saving mouse coordinates in array ,for this i have followed following steps: Firstly check ...
1k views

CWT for filtering / feature extraction

I had asked a question last night in regards to how to process my data (Noise rejection / feature extraction) but I have a more specific question now that I hope someone can answer. As mentioned in ...
336 views

Measure similarity between quantized grayscale images

I want to measure the similarity between quantized grayscale images (8 levels) that mostly depict organic patterns found in nature, say pigmentation patterns in animals (zebra pattern, leopard spots,.....
123 views

Feature matching of images without corners

I am trying to stitch aerial images using feature-based registration. Most image pairs are matched well, such as this: Others are not matched due to lack of common features: As you can see, the ...
4k views

difference between Gabor and log-Gabor function

I am reading a paper using log-gabor filters for feature detection. I was thinking about the difference between Gabor filters and log-gabor filters. Can anyone tell me the difference(s), and a way to ...
4k views

Should I use CV_HAAR_SCALE_IMAGE while using LBP CascadeClassifier?

I trained a cascade-LBP to detect Lollipops with 1000 images, now I'm trying to "adapt" the openCV HAAR-Cascade example to use my LBP trained .xml but I'm not sure about the "HAAR_SCALE_IMAGE" flag, I ...
46 views

Get level of wellness in a cascade classifier using LBP

I'm currently working in a Lolipop LBP cascade detector using OpenCV. The training is correctly done and the cascade classifier detects the sticks of the Lolipops correctly but with some minor errors. ...
329 views

How to match a thumbnail to an area in the original image?

Suppose that you have a thumbnail and the original image from which it was generated. You need to match the thumbnail to an area in the original image that represents the original selection from which ...
1k views

Structure Tensor vs. Hessian Matrix

Hello can someone explain the semantical meaning of the structure tensor and the Hessian matrix. I am aware of how it is calculated, but i find it difficult to comprehend what they describe in the ...
96 views

Moravec, Harris noisy window

Harris and Stephens writes about the interest window of Moravec: "The response is noisy because the window is binary and rectangular", and suggests applying a Gaussian window. My Question: ...
3k views

Why is LBP generaly faster than HAAR?

I am digging into Haar like and LBP features. More precisely its implementation in OpenCV. Every article or forum entry I found states, that LBP is faster than Haar. My local tests also confirm this ...
974 views

texture matching between patches of an image

I have an image A which I have divided into 4 x 4 subband images. For a given patch P1 in ...
181 views

pre-processing to improve feature detector before tracking

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 ...
121 views

what is in intuitive explanation of local derivative pattern (LDP)?

Zhang et al. proposed the LDPs for face recognition . They considered the LBP as the nondirectional first-order local pattern operator and extended it to higher orders ( th-order) called the LDP. is ...
457 views

Efficient Hessian-Laplace blob detector implementation

As it is mentioned in a paper for SURF, it is possible to approximate hessian determinant using integral images. If I want to implement Hessian-Laplace detector, is it feasible to also approximate ...
231 views

Need critical help: How to detect and distinguish two very similar looking signals?

Hi guys I have a really tough signal processing question here. How do you detect and distinguish two very very similar looking waves? I need to distinguish between these two signals for an online ...
310 views

Detecting sound inside a sound

I was searching on the Internet hopelessly about some materials regarding detecting a sound in another sound. Say, I've got a recorded short sound (which may be anything, fragment of speech, fragment ...