Questions tagged [computer-vision]

Computer vision includes methods of processing, analyzing, images and high-dimensional data to form high level understanding and recognition of the scene or images.

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Is there any good book regarding 3D reconstruction from 2D images? I prefer to work in MATLAB

I am working on a project regarding 3D reconstruction of 2D images. I have understanding of finding and Mathcing the keypoints and its algorithms; but i am not able to replicate the theory in MATLAB ...
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What is localizability in Computer Vision?

Please consider the following excerpt (from Rodrigo R, Zouqi M, Chen Z, Samarabandu J.: Robust and efficient feature tracking for indoor navigation): Robust feature tracking is a requirement for ...
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why eigenvalues concerned in Harris corner detection?

In Harris corner detection, as I see, the goal is to find out those points $(x,y)$ which makes $S(x,y)$ a large value for any direction of shifting, $$ S(x,y) = [\Delta x , \Delta y]M\left[ \begin{...
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313 views

How can I automatically find the boundary of a high intensity region inside an image?

I have an image I(x,y): Red indicates high values and blue low values. Everything in black is drawn onto the image afterwards. The black dot (xp,yp) represents a point clicked by an user and the ...
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1answer
603 views

Approximating pixel location in scale space

I'm implementing a scale-space with o octaves and s scale levels in each octave. Each octave is half the size the previous. I have keypoints found in each octave, I need to approximate the real ...
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840 views

Triangulation from set of points from left camera

in my program there are stereo cameras. The cameras were stereo calibrated. I have a set of 2D-Points from left image (for example, it could be some Harris Corners from left images). And the task is ...
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Can you average out focal length from different camera calibration sessions?

If I perform a number of camera calibration routines at a fixed resolution, with various sizes of calibration patterns (like checkerboards), at various distances and get various values for focal ...
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188 views

Constant used to determine the minimum samples in Compressed Sensing

A key result in compressive sensing states that, with high probability on the random draw of an $\ m × N$ Gaussian or Bernoulli matrix $\ A$, all $\ s$-sparse vectors $\ x$ can be reconstructed from $\...
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523 views

Safe Point Thinning Algorithm - How to?

I am relatively new to image processing and am working on a project that requires the thinning of binary images. In the literature, I've seen references to the Safe Point Thinning Algorithm(SPTA) ...
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1answer
257 views

Algo Name: Detecting Elongated Shape in 2D Image by Convolution with Directed Lines

I am detecting a shape with roughly known orientation (obtained by using Hough line transform) in thresholded binary image by convolving the image with line with that orientation, and counting the ...
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1answer
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How can I track detected objects from frame to frame

I want to track people's faces in a video stream (like a security camera), but I am running into a problem. I was using a Haar classifier to find the faces and sending the detected faces to a system ...
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1answer
83 views

Confusion regarding Sobel operator

I am taking computer vision course, where I learned about Sobel operator for detecting edges. I somewhat understand how it works as described here. But I have a basic confusion. The operator can be ...
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Camera calibration using multiple images

I am trying to get the hang of camera calibration. For this purpose, I have mainly watched this lecture on youtube: Lecture 12: Camera Model by UCF CRCV. I believe that I understood the main ideas: ...
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Would the locations of SIFT features generally agree with features detected by Shi-Tomasi method?

I am having a comparison of different feature detection methods. So if we compare the SIFT (Scale-invariant feature transform) and Shi-Tomasi method, will their feature locations agree and why? Are ...
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59 views

which spatio-temporal properties does dynamic textures exhibits?

know that dynamic textures are spatially repetitive and temporally varying patterns. 1.I read one sentence in one paper i.e. They are sequences of frames exhibiting certain stationarity properties ...
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Edge detection on a color image

I understand the process of using a Sobel kernel for edge detection in greyscale images. The input is a greyscale image, and the output is a greyscale image. I'm having trouble, however, figuring out ...
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916 views

Vector Quantization in Hidden Markov Models

In the field of Gesture Recognition and Speech Recognition (using HMM classifiers), do multiple HMM classifiers (one for each class) share common Codebook (i.e common set of symbols) in Vector ...
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After advice about detecting focus quality of objects in a photo detected using YoloV3

I've spent the last couple of days playing with YoloV3, and have had very good results. My use case is sports photography, and the object detection for people/bikes etc is very very good, I'm very ...
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1answer
147 views

How to segment multiple overlapping coins (ellipses)

I am doing a program that counts coins (and tells their value by their size) with OpenCV (C++). Let's say we have an image of some coins. If there is an overlap of two coins at the same time, it is ...
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342 views

What Are the Differences between Super Resolution, Denoising and Deblurring?

In the fields of computer vision and image processing, what are the differences between Super Resolution, Denoising and Deblurring?
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Which is correct representation for function of variable?

I have a function as $$E=\int_\Omega -\log\big( p_i(x)\big) dx$$ where $p_i(x)$ is density distribution which estimated by Parzen window method. $$p_i(x)=\frac{1}{\Omega_i} \int_{\Omega_i}K_\sigma\...
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Can disparity range from negative to positive values for parallel cameras?

In my stereo-rectified camera pair (not physical, but two positions of the same camera), when I project some 3D points in both images to find a rough disparity range, I often get a range that goes ...
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Efficient Marker Detection for Images

I need to detect a known number of simple markers (chessboard patterns) in a color image efficiently. I implemented normalized cross correlation (NCC) as a pixel shader via WebGL since I need this to ...
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1answer
118 views

Pyramid Match Kernel: How to fit grid around data points?

I am planning to use Pyramid Match Kernel method for object recognition from depth images: I am going to extract a set of feature vectors $x \in \mathbb{R}^d$ for each object instance and then I want ...
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1answer
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Histogram Intersection with two different bin sizes?

I have two images: A and B. Image A is a screenshot of image B, the original image. While there is noise in image A, the original features are still distinguishable. Histogram intersection tells us ...
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620 views

Planar Homographies in MATLAB

I have taken an image in height 2 meters of the ground as the original image and I want to simulate another image in 50 cm's of the ground, such as the simulated image. The focal length of my camera ...
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1answer
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What is intensity centroid?

So, I am reading a paper about ORB and it happens to calculate the direction of corner from it center . According to Rosin the author of the paper;moments of a patch is given by and the centroid is ...
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Is there any good book regarding Image Processing Algorithms for Feature Extraction and Matching which gives examples in MATLAB?

I have been looking to implement feature extraction and matching in MATLAB. For this, I've read many algorithms, but i'm not able to understand how to implement these in MATLAB. Is there any Book ...
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1answer
783 views

Particle filter, resampling step implementation

I am not very good in statistic neither in probability theory, and I do not completely understand the mathematical background of Monte Carlo simulation or SIR sampling, but I'd like computer vision ...
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2answers
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Segmenting wood chips in an image

I am trying to recognize the wood chips in the image shown below. The ultimate goal is to try and recognize the width and length of each wood chip. Currently, I am using an approach that involves ...
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3answers
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Visualize visual words in bag of words model

I am implementing visual bag of words through these steps: Find interest points using SIFT Calculate SIFT descriptor Build codebook through kmeans clustering of SIFT descriptors. How can I visualize ...
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1answer
159 views

Histogram operation for improving visual object tracking

I'm developping a people tracking with nearest neighbour data association technique and kalman filter for smoothing/predicting. The tracker works quite good but sometimes it mismatch objects if they ...
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1answer
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Hand detection in matlab

I am beginner and I want a help to know how to detect hand in Matlab. First, I need code which detects skin and then draw a rectangle around a region so it show to me face and hand. When I try to ...
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1answer
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Image processing: using PCA for 3d object recognition

I read this lecture on using PCA/eigenfaces: http://www.cse.psu.edu/~rcollins/CSE486/lecture32.pdf And I want to use this general procedure to recognize a 3D clay model that I took pictures of from ...
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1answer
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How to relocate face points in opencv / face distortion?

I have to simulate facial expressions on a face image ( say open mouth ). For this I first extracted the facial feature points and found the corners of the lips. Now I need to deform the image by ...
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1answer
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Matching features points of rotate image using SURF

I'm trying to match SURF points between 2 images using SURF with opencv. One is the rotation of the other. The problem is that the few matching it can found are wrong. image of matching points I ...
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1answer
593 views

Color Tracking a Red Laser Height

I'm making a Laser Harp [https://en.wikipedia.org/wiki/Laser_harp]. The application needs the position of the hand along each of the laser beams to modulate a sound synthesis or modify the properties ...
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Object Recognition using bag of features using matlab [closed]

I want to write a MATLAB program for simple object recognition using bag of features. In short, I want to first extract the features from an image, create a visual library using those features, then ...
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1answer
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List of all available ARM+DSP processors for surveillance

I have come across TI's C6000/Integra. I want to know is there any other similar or better ARM+DSPs available. Specially for surveillance/vehicle number plate recognition etc. Having camera input at ...
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74 views

Given some parameters, how do you determine how much of an image sensor an object will consume? [closed]

If I have the details of a scene and a camera, how can I tell how much of my camera's image sensor will be taken by a certain object in space? For example, if I have a painting that is 1m by 1m, it ...
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1answer
530 views

How is WSNR (weighted signal to noise ratio) defined?

I'm studying about comparison between images to determine quality. I've learned about MSE, SNR and PSNR, and now I'm trying to understand WSNR, which I assume is similar to SNR but with weights. I ...
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Why do we need 4 points for homography but 7/8 points for fundamental matrix calculation?

Sorry if this is a trivial question but I could not find a suitable answer elsewhere. I recently learned about homography and fundamental matrices in a CV class. I understand how these matrices are ...
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1answer
217 views

What does photon noise mean in digital image processing or computer vision?

From this link: Photon noise, also known as Poisson noise, is a basic form of uncertainty associated with the measurement of light, inherent to the quantized nature of light and the independence of ...
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2answers
660 views

Techniques for detecting small blobs in noisy images

I am trying to write a program that uses computer vision techniques to detect (and track) tiny blobs in a stream of very noisy images. My data is of two types: one set of images are not so noisy, ...
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2answers
430 views

Kalman filter for tracking obstacles

I'm developing a Computer Vision project in Matlab as an aid to visually impaired people. The setup would be a stereo pair of cameras which the blind person would carry. Using this stereo information, ...
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3answers
108 views

Background averaging not working

I'm working on a problem where I'm trying to use background averaging to see what the frame looks like in a beehive behind the bees. I've been trying to use standard averaging (I take an image every 1 ...
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1answer
54 views

Why is this projection wrong?

I am trying to figure out why a 3D cube doesn't project in the right place in the image. I start with the camera at origin and the cube centered at (0,0,1) world ...
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1answer
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What is an approach in computer vision that can be used for tracking players in hockey games?

It differs from human tracking in random environment in that detail that we have fixed environment. And players move pretty fast and it is important to resolve collisions and occlusions, keep track of ...
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1answer
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How to extract text from a scanned document?

The task I am facing is extraction of rotated text (any angle) from a scanned image(attached Image). The image contains a blue sticker on it and need means in extracting the text (printed text) from ...
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2answers
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why the sum of masks should be one?

I am studying pyramids (expanding and reducing) and I am a newbie. Why sum of the convolution mask should be one when we are using Gaussian distribution? According to When should the sum of all ...