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Questions tagged [computer-vision]

The goal of computer vision is an automatic extraction of information out of images. It includes methods for acquiring, processing, analyzing, and understanding images and high-dimensional data from the real world in order to produce numerical or symbolic information, e.g., in the forms of decisions. The image data can take many forms, such as video sequences, views from multiple cameras, or multi-dimensional data from a medical scanner.

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12 votes
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Quickly finding rough lines in sets of points

In a particular class of detectors, our data comes out as pairs of points in two dimensions, and we want to string these points into lines. The data is noisy, and is binned in one direction but not ...
dmckee --- ex-moderator kitten's user avatar
9 votes
2 answers
4k views

Markov (Chain) image generators?

Markov Chains can be used to generate, or auto-complete, text. https://en.wikipedia.org/wiki/Markov_chain#Markov_text_generators Training text is read, and some information about the text is ...
alan2here's user avatar
  • 193
8 votes
2 answers
705 views

Matrix free finite elements method for visualization in process tomography

I am Computer Scientist and now I am interested in matrix multiplication on GPUs. My research are focused on matrix free finite elements method where I multiply sparse matrix. Sparse matrix could ...
Konrad's user avatar
  • 95
8 votes
1 answer
5k views

How does each process in bag of visual words image classification work?

I hope this is on topic, I found this through the proposal here: https://area51.meta.stackexchange.com/questions/320/shall-we-unite-computational-science-proposals A good visual description of BOW: ...
mugetsu's user avatar
  • 183
7 votes
2 answers
171 views

Classification of observations depending on its trajectory

I'm afraid the title is terrible, but I don't know how to summarize this problem in a few words. Using an instrument, we are monitoring the trajectory of several objects during a period of time. We ...
siritinga's user avatar
  • 203
7 votes
1 answer
184 views

Conjugate Gradient with Hierarchical Basis Functions: How can the hierarchical base be decomposed?

I'm trying to implement a Conjugate Gradient solver using Hierarchical Basis Functions, following this paper. In section 3 the paper says that the hierarchical basis matrix $S$ can be decomposed into ...
rsp1984's user avatar
  • 435
6 votes
2 answers
2k views

Interpolation by Solving a Minimization Problem (Optimization)

I will try to give the motivation behind this problem and later the math formality. Given a grayscale image (1 Channel - $M \times N$ Matrix). Someone marks some pixels as anchors. Now, you need to ...
Royi's user avatar
  • 332
6 votes
0 answers
343 views

FEM : energy minimization VS PDE solving

Engineering FEM When I studied engineering, I learned the traditional approach for finite elements for elasticity. The point was to solve the PDE $-div(\sigma)=f$ as: Multiply your PDE with a test ...
Txnda's user avatar
  • 61
5 votes
2 answers
4k views

Algorithms to extract trajectory lines out of 3D point clouds

I am looking for different approaches to extract 3D polylines out of Point Clouds. We are able to create these point clouds out of different data sources of real world surveys (LIDAR, RADAR, etc...) ...
Jürgen Zornig's user avatar
5 votes
2 answers
779 views

Compute point-spread-function between original and blurred image

Take an image $f$ with some characters on it (below, hjFu3). Let's apply a filter $h$ on it to obtain a second image $g$ where the text is not visible. Is there a way to compute what kind of filter $h$...
Smilia's user avatar
  • 468
5 votes
1 answer
172 views

How to train a model to classify object trajectories?

I have a tracker that outputs the trajectory $(x,y,z)$ of an object (e.g., a can). I want to use these trajectories to train a classifier (i.e., SVM) in order to infer the activity that the person ...
Gianpiero Francesca's user avatar
4 votes
1 answer
3k views

Shearing and Hartley's rectification

I'm using Richard Hartley's rectification algorithm to rectify a pair of images before performing stereo disparity computation. The problem is I'm observing shearing in one of the rectified images and ...
TH.'s user avatar
  • 226
4 votes
2 answers
204 views

Detect all geometric objects in an (edge) image

EDIT: Added another, more suitable, example below. Disclaimer: With edge map I mean an image given as bitmap just consisting of black and white pixels. Short description: Briefly, I'm searching for ...
ellipsoid's user avatar
4 votes
1 answer
559 views

Methods to implement floor dirt detection algorithm

I'm trying to detect dirty floor areas in a series of images, using MATLAB and its Image Processing Toolbox, like the one that follows: In the image above, there are two distinct areas, the whiter ...
R_Est's user avatar
  • 41
4 votes
0 answers
478 views

Open source implementation of Multiscale Combinatorial Grouping

I would like to use Multiscale Combinatorial Grouping for my PhD research. However, I am restricted to use open-source implementations and this one runs on Matlab. Does anyone know of an equivalent ...
Sophie Crommelinck's user avatar
3 votes
1 answer
512 views

Evaluate 3D Shape Descriptor

I'm trying to create my own 3d shape descriptor, the idea is that how I may evaluate how much my descriptor is well and good? What I checked is that they evaluate descriptors through shape matching, ...
R.K's user avatar
  • 43
3 votes
3 answers
112 views

Where can I find public datasets of images mostly dominated by contour?

I am about to start research for my thesis. I am trying to find public datasets of images mostly dominated by contour meaning (An outline, esp. one representing or bounding the shape or form of ...
Penumbra84's user avatar
3 votes
1 answer
609 views

Fitting a grid to an STM image

Suppose I have a scan from an STM image (very much like the things you see here). Suppose I have a simple square lattice with lattice parameter a. What I'd like to do is to numerically find the ...
Lagerbaer's user avatar
  • 487
3 votes
1 answer
220 views

How do you formulate the linear least-squares method for radiometric calibration?

In Debevec and Malik (mentioned similarly in Forsyth and Ponce's Computer Vision: A Modern Approach) they highlight a method of solving the camera response function using linear least-squares. We ...
Felix Fung's user avatar
3 votes
1 answer
185 views

Recover curves from noisy collection of points

Background: I'm trying to make a system that tracks a number of bubbles in a video I'm implementing the bubble detection in the single image case using the Circular Hough Transform. Due to occlusion,...
Alex's user avatar
  • 31
3 votes
0 answers
62 views

Calculating depth mask from different lighting

I have a object which is static, the camera is static and light source is moving. How can the depth mask be calculated ? Concept is to use - calculate height from shadow length Lets imagine a have ...
Maifee Ul Asad's user avatar
3 votes
0 answers
152 views

Explanation of LidarBoost Algorithm?

I am trying to understand the LidarBoost algorithm as explained in this paper (PDF warning). My apologies if this isn't the appropriate exchange; I've posted in DSP, but I didn't get a response there, ...
anjruu's user avatar
  • 203
2 votes
2 answers
1k views

Fitting orthogonal planes to a point set

I have a set of 3d points to which I want to fit two planes. I know the assignment of points to the planes so I don't need any RANSAC or similar. Currently, I'm using a PCA-based approach to fit two ...
FooBar's user avatar
  • 133
2 votes
2 answers
143 views

How to find fundamental matrix based on other fundamental matrix and camera movement?

I am trying to speed up some multi-camera system that relies on calculation of fundamental matrices between each camera pair. Please notice the following is pseudocode. ...
Gulzar's user avatar
  • 121
2 votes
1 answer
80 views

Algorithm to determine flat surfaces and camera orientation without specialized hardware

Modern augmented reality platforms such as Google's ARCore and Apple's ARKit seem to only operate on mobile devices, I'm guessing, because their underlying algorithms require specialized hardware that ...
hotmeatballsoup's user avatar
2 votes
1 answer
124 views

Polygon approximation with a circle

There is an article describing how to detect a pupil from an eye photo. A.-H. Javadi, Z. Hakimi, M. Barati, V. Walsh, and L. Tcheang, "SET: a pupil detection method using sinusoidal approximation," ...
Mikhail Seryukov's user avatar
2 votes
1 answer
284 views

Integral image resizing

I'm trying to find an approach for integral image resizing. I found out that I can do it with a bilinear interpolation method, but with this approach I can only resizing by the factor which is a power ...
mariuszs80's user avatar
2 votes
0 answers
101 views

Efficiently detect overlaying ellipses in distorted images

I'm currently facing the problem of efficiently detecting (special) ellipses in edge images. These images are given (i.e. previous image processing is impossible) and contain quite some noise. I need ...
hello_darkness's user avatar
2 votes
0 answers
95 views

Video frame homography alignment

My project requires me to track objects such as cars via a drone. I have a live video stream in which I would like to detect and track objects, the view doesn't change that much as the drone is nearly ...
Andrey's user avatar
  • 21
2 votes
0 answers
77 views

Alternatives to breadth-first-search in 3D grid cluster detection?

I've got a question about a good way to find the quickest algorithm for my problem: problem: I've got a 3D cubical grid containing voxels that are either 1 or 0. It is stored as a flattened array. If ...
SumakuTension's user avatar
2 votes
0 answers
58 views

Fitting a plane with the Prewitt gradient operator

Prewitt gradient operator Show that the Prewitt gradient operator can be obtained by fitting the least-squares plane through the 3 × 3 neighborhood of the intensity function. Hint: Fit a plane to ...
ecjb's user avatar
  • 141
2 votes
0 answers
182 views

Pure math questions arising in computer vision, and the need for mathematicians to solve them [closed]

I've read in several articles/answer written by CS (grad) students or other people that the advanced knowledge of pure math that's required for certain areas of computer vision is sometimes too high ...
Mathmath's user avatar
  • 129
2 votes
0 answers
80 views

Environment for implementing/testing Computer Graphics algorithms [closed]

I need to code up a computer graphics algorithm for Surface Registration. Briefly surface registration is the process of finding "optimal" one-one correspondence between surfaces, where the meaning ...
smilingbuddha's user avatar
2 votes
0 answers
74 views

Network Flow - based optimization in renowned paper appears to have a wrong step

This is probably going to be an easy question for most people and embarass me. I've been reading the Zhang et al. 08 paper on detection-based tracking through network flows: http://iris.usc.edu/...
Jason's user avatar
  • 121
1 vote
1 answer
1k views

Iterative camera calibration - No convergence

I am trying to implement the algorithm from the research paper "Accurate Camera Calibration using Iterative Refinement of Control Points" from Datta et al. Running many iterations does not show a ...
Toyo's user avatar
  • 113
1 vote
2 answers
604 views

Image recognition on Raspberry Pi

I'd like to distinguish different types of beers in my fridge using a Raspberry Pi. I saw a very good tutorial on Adafruit that utilized OpenCV for face recognition. Can these same face recognition ...
Anconia's user avatar
  • 111
1 vote
3 answers
807 views

Algorithm: Extracting motion frequency from video

I was wondering if anyone knows of any algorithms or projects that can detect the frequency of a motion from a video clip. Like if I had a video of a bouncing ball with constant frequency, could an ...
Nate's user avatar
  • 11
1 vote
1 answer
95 views

Can software remove all distortion from image taken with 180-degree lens?

If this isn't the right SE site, please suggest the right one? Can software remove all distortion from a 180-degree lens? In other words, if the goal is to optimize for distortion-free images, would ...
Crashalot's user avatar
  • 111
1 vote
1 answer
135 views

Is it possible to locate an image in a video using MATLab?

I'm not a huge programmer, but if it'll save me lots of time, that's when I code (given that it's possible). I know MATLab has a Computer Vision Toolbox, so my question is: is it possible to program ...
Eric's user avatar
  • 11
1 vote
1 answer
596 views

What is Precision-Recall Curve? [closed]

I have a data mining assignment where I make a content-based image retrieval system. I have 20 images of 5 animals. So in total 100 images. My code returns the 10 most relevant images to an input ...
jeff's user avatar
  • 121
1 vote
0 answers
60 views

Guaranteeing that the numerical approximation to $B = K^{-T}K^{-1}$ is positive definite in Zhang's algorithm

In Zhang's Algorithm to determine the intrinsic parameter matrix $K$ (see here for slides talking about this), we instead compute the matrix $B = K^{-T}K^{-1}$ since we obtain a linear system in the ...
matpiliya's user avatar
1 vote
0 answers
35 views

SHREC 2010 Descriptors

I will appreciate if I may find someone how can clarify for me the part regarding the quality of feature descriptor, shown in the figure below: and this screenshot is from the article: SHREC All my ...
R.K's user avatar
  • 43
1 vote
0 answers
58 views

Mathematical physics applications in present-day image processing

During the past few years several important areas of image processing and image classification or generation became dominated by convolutional neural networks. I'm interested if there are any methods ...
nikkou's user avatar
  • 111
1 vote
0 answers
224 views

Is it possible to generalize the two view Sampson error to multiple view cases in computer vision?

In multiple view geometry of computer vision, there is a geometric error called Sampson error which is very useful in the nonlinear estimation of fundamental matrix....
LCFactorization's user avatar
1 vote
0 answers
1k views

Pixel-To-Angle Transformation in Camera Image

I'm trying to localize points I see in a camera image in terms of azimuth and elevation and match points between shots. Individual shots should differ only in rotation around the camera's center (...
Johannes Bauer's user avatar
0 votes
1 answer
2k views

A Filter is Sum normalized to 0 and square normalized to 1

Firstly, About the Hierarchical Model And X (HMAX model), i still don't understand what is the difference between the "Original model" and "Standard model". Does in Standard, we use imfilter not conv2 ...
Christina's user avatar
  • 101
0 votes
1 answer
224 views

Is the inverse radon transform considered a linear operation?

I wanted to know if practically the inverse radon transform operation is considered linear and would be a good candidate for the application of compressed sensing. To my understanding it should be ...
syed's user avatar
  • 1
0 votes
1 answer
153 views

Rank of image intensity matrix

I've been reading a paper about using Matrix Completion for Photometric Stereo but I am having some troubles in section 2.2 trying to understand why irrespective of the number of pixels and the number ...
BRabbit27's user avatar
  • 1,029
0 votes
1 answer
2k views

How to detect smiles using OpenCV and IntraFace?

I have installed OpenCV and IntraFace, now the code can detect landmarks on the face, like this : Now how can I convert this to a smile detector? I have the landmark points as an array, so I should ...
jeff's user avatar
  • 121
0 votes
1 answer
229 views

How to recover the 3x4 pinhole camera from 9 parameters

I downloaded the bundle adjustment data from this link: original data for bundle adjustment which is the supporting data for a paper titled: Bundle Adjustment in the Large I want to use the data ...
LCFactorization's user avatar