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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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Skewed rectified aerial images

I have a series of aerial images from which I would like to get disparity maps for every consequent pair. In order to do that I do a stereo rectification. The problem is that sometimes rectified ...
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1answer
57 views

Suggest an image segmentation technique to find the paste radii?

I am new to MATLAB/Digital Image Processing. So pardon me for any typing errors or wrong use of jargon. 1) I am trying to find the paste diameters for a total of 100 images in sequence. I am posting ...
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Signal processing methods for identification of multimedia descriptors for feature extraction (semantics)

It is said in https://www.amazon.co.uk/Multimedia-Semantics-Metadata-Analysis-Interaction-ebook/dp/B005E8AG66 that While there has been a lot of work in the signal processing research community ...
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41 views

Scan an Auditorium, Count People, and Display Open Seats

I'm looking for any recommended approaches to be able to digitally process a room full people, like an auditorium or a movie theater and output the following information: Goals: How many people are ...
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1answer
33 views

Is there a closed form solution for a temporal calibration of two different signals?

Given two signals $f_1(t),f_2(t+dt)$ where $t$ is time and $dt$ is the time delay between the two signals, is there any closed-form solution with respect to $dt$? what are the efficient global ...
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2answers
423 views

Camera measurement of heart rate - frequency bias towards 50 bpm (0.83 Hz)?

I am trying to develop a RGB camera-based non-contact measurement of heart rate using principles of remote photoplethysmography. I want to be able to measure a range of heart rates I have been looking ...
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26 views

Given a image of white lines forming a grid, how to get masks of the interior shapes using opencv?

I am trying to determine if there are pills in different cells of a pillbox. I have a raspberry pi camera that takes pictures of a pillbox at regular intervals. I would like to use computer vision ...
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29 views

How to produce pencil-like images by pure image processing methods?

Is it possible to reproduce the following pencil-like image by pure image processing? Notes: The original image: Fig 10 in paper http://www.cs.columbia.edu/cg/aircode/aircode-uist-2017-li-et-al.pdf ...
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What is the most reliable shape representation for the purpose of detecting humans shapes?

The requirement of the algorithm is to detect human shapes. While the standard HoG or Harr cascade can be used, I am exploring whether the human shape - which primarily includes face+neck+upper-torso ...
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41 views

How to measure relative distance (Y axis) between two physical objects? - AR app

I am currently developing an AR app that reacts to various positions of physical objects (lego-like bricks) that are placed on the desk in a real-time. If I place the first block on the desk and ...
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244 views

How can l get dense optical flow on superpixeled consecutive frames

l would like to compute dense optical flow over two consecutive frames frame 1 and frame 2. ...
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134 views

Best approach to check the result of color space conversion from RGB to LMS?

I'm currently working on manipulating the order of RGB color from an image into RRB, GGB, etc. Now I need to convert this RGB value into LMS. I take this paper as a reference for the transformation ...
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1answer
49 views

What is difference between along the edge and across the edge

I am trying to implement a paper called structured tensor based image interpolation. In the paper I came across a concept called tangent direction and normal direction. What they mean is tangent ...
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2answers
1k views

Camera calibration and extrinsic parameters for perspective transformation

I'm working in a photogrammetry camera and laser application where I need to measure a displacement in a specific plane, this is a quick diagram of the setup: In order to get proper measurements I'm ...
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1answer
257 views

Block normalization of histogram of oriented gradient

I am a beginner in image processing. I have some questions regarding HOG. https://www.learnopencv.com/histogram-of-oriented-gradients/ From this website, it mentioned that each element inside the ...
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1answer
763 views

MatLab - Can not detect all lines in a “simple” image using houghlines

I try to detect all lines in an image with some common geometric figures. The obvious choice, hough of MATLAB wouldn't print out the desired results. I used the ...
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1answer
2k views

Line Detection with OpenCV and Python [closed]

Why do we get less amount of lines then desired in line detection using HoughLines tranformation from OpenCV? How could we improve this method and get all the lines appearing in the image? I would ...
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2answers
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Shadow removal opencv python

How do I remove a shadow after MOG2 background subtraction using OpenCV Python? I used all morphological operations, gaussian and median blur, thresholding. it removes noises but deep shadow is ...
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472 views

Resolution and accuracy of a stereo camera

My question is pertaining to how the parameters of a stereo camera system (focal length, base, height, pixel density) affects the accuracy as well as the resolution of depth measurement. I do not ...
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1answer
854 views

Calculating distance between two blobs in a binary image in microns

I have a monochrome CCD camera with resolution 960 X 1280 and can give up-to 15 fps I am working on python opencv. I want to track the distance between two rectangular blobs in binary images in real ...
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61 views

How to overcome effect of intensity variation in image processing?

I want to process an image for which I need the method to be robust to lighting conditions. For that the only thing I can think of is normalising intensity. I did this by dividing the image with ...
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51 views

Best focus image of stack

I am trying to find the image which has the optimum focus of a focus stack (10 images). I am able to find the best two images by using the minimum gray intensity values but now the problematic part ...
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119 views

OpenGL Image warping using lookup table [closed]

I am working on an Android application that slims or fatten faces by detecting face. Currently, I have achieved that by using Thin-plate spline algorithm. http://ipwithopencv.blogspot.com.tr/2010/01/...
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1answer
373 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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1answer
349 views

Edge detection in low contrast images

I have some images which have some objects of my interest. The objects have very low contrast w.r.t. background and I would like to detect the edges of these objects in these low-contrast images. Any ...
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1answer
36 views

How to choose good features for my machine vision application? [closed]

I am trying to create an application (with OpenCV3) that can distinguish sidewalks from streets by a real-time camera that is embedded in a glass. I have 3 question about this project: Which features ...
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1answer
871 views

Detect circles in image

I have an image that has pixelated circles in it (a cross section of wires). I want to identify the wires, their location and count them. The circles never overlap and the wires are all within a 95% ...
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1answer
47 views

How does the bandlimit of an image reduce by an octave in Gaussian Pyramid procedure?

Reference paper 1. For arguments sake, let's say that the maximum and minimum frequency in an image are 256Hz and 1024Hz. When I perform filtering using the gaussian function, the "bandlimit" reduces ...
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1answer
103 views

Frame overlapping

I 'm reading the following article from NVIDIA which involves some audio processing a the beginning : link just here (part 3.2) I don't understand the following part : In practice, we use 520ms ...
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1answer
228 views

Pattern matching methods: Based on Area and Based on features

Good morning, I'm new to image processing and I'm currently working on a project for pattern matching and OCR more specifically. In the state of art I've found the matching process can be classified ...
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2answers
529 views

What happens when we reconstruct a signal after its Fourier transform is done and some frequencies are altered? [closed]

Since we loose time information when we take a Fourier transform, what happens if we alter a few frequencies from the transform and then reconstruct the signal, do we get the altered frequency at the ...
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1answer
24 views

Are there paper about black box testing of optic flow algorithms?

Do papers exist about comparisons of the resulting optic flow and its precision compared to the used optic flow method? I would like to find paper that dealt with this topic in some way and had ...
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1answer
47 views

Would it be possible to reconstruct 3d trajectory of ball projectile using only monocular video

Assume ball location on the image frame in each timestamp is given. Would it be possible to reconstruct the ball's 3d trajectory in the camera's coordinate frame? The ball should be able to ...
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1answer
180 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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2answers
308 views

How should someone start to learn machine learning and computer vision for mobile applications? [closed]

I am very interested in learning Machine Learning and Computer Vision for mobile apps, for iOS and Android. But I have no clue or even a slight idea on how to even begin. I know this is heavy on math ...
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1answer
109 views

Super resolution methods

I am working on the project where my goal is to create SR image from 25 LR images that are precisely shifted by 0.2px (both in horizontal and vertical direction ). I also know that the captured object ...
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Get the correct solution for rvecs and tvecs for camera pose estimation, using SolvePnP in OpenCV C++

I am trying to measure the pose of a camera and I have done the following. Mark world 3-D(Assuming z=0, since it is flat) points on corners of a square on a flat surface and assume a world coordinate ...
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Issue with Camera Pose estimation with OpenCV SolvePnP function

I am trying to find the position of the camera in a world(reference) coordinate system which I have created using markers on a sheet. These points lie on a square corners of length 12.8cm on ground. ...
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1answer
674 views

How to choose the most appropriate color space for a computer vision application?

A lot of image processing techniques used in computer vision consist (among other things) in switching from RGB to another color space (HSV, YUV, LMS...) : color transfer, visual tracking... It seems ...
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1answer
127 views

Are the HOG features of the images good enough to do image classification alone? Why are their variances low?

I've also asked this question here:https://cs.stackexchange.com/questions/77884/are-the-hog-features-of-the-images-good-enough-to-do-image-classification-alone I've been working on classifying human ...
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1answer
305 views

Difference between Generalized Hough Transform and Cross-correlation Feature Matching

I've been taking the Udacity Computer Vision Course, and one thing that has confused me so far is how the Generalized Hough Transform is any different from feature matching on an edge image using ...
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4answers
359 views

Palm Pilot Graffiti

I have been completely unable to find details on the underlying model that is used for the Palm Pilot Graffiti handwriting recognition. Given the computing power available for handheld PDA technology, ...
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1answer
107 views

Pinhole camera model from houdini parameters

From a simulation with Houdini software I retrieved these parameters: Camera position: -0.675839, 33.5945, 0.0318854 Camera Rotation: 0.0318854, 92.4693, 0.1 Focal Length: 52.5172 mm Image size: 1920 ...
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0answers
170 views

stones' detection in jewel image

The project I am doing is to detect stones in an image of a jewel, so as to get the idea of the deduction to be made in the gross weight of the jewel. I have done image-segmentation in the HSV color ...
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0answers
528 views

Correct Fish Eye camera Radial Distortion and blurry effect at the image edges

There are a lot of questions regarding this topic ,but I am trying to get a more clear picture from these questions. I am trying to calibrate a fish eye camera and I am using OpenCV omnidir class ...
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0answers
334 views

What are the drawbacks of Harris corner detector? [closed]

What are drawbacks of Harris corner detection when trying to match features in a stereo pair? I notice that whenever I use Harris corner detector to match features, images with strong occluded areas ...
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1answer
87 views

Estimating exterior camera parameters by matching lines using least square estimations (Lowe, 1991)

I'm new to computer vision and graphics. I want to estimate exterior camera parameters using non-linear least square estimation as suggested by "Lowe, David G. "Fitting parameterized three-dimensional ...
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27 views

Kalman Filter - Gaussian representation

I'm trying to understand well the kalman filter, as a result i'm having this question : Why do we represent noise with a Gaussian ? what does this really mean intuitively ?
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417 views

How can l extract characters withe same bounding box size?

l have a set of images which represent a sequence of characters. l'm wonderning whether OpenCV can segments and crop each character from the image with same bounding box size. My numbers are not ...