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Questions tagged [opencv]

OpenCV (Open Source Computer Vision) is a cross-platform library of programming functions for real time computer vision.

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Help in Retraining a HOG Descriptor using SVMLight

I am currently trying to count cars using OpenCV 2.4.4 with a HOG descriptor. Because a model for car detection is not available in OpenCV, I am creating my own model using SVMLight and a dataset of ...
bonchenko's user avatar
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5 votes
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Is rotation of a Fourier transform the same thing as Fourier transform of a rotation?

I'm working on an image processing problem and wondering if DFT(rotation(image)) == rotation(DFT(image)) (1). My final goal is to apply rotations in the Fourier domain then do an inverse Fourier ...
Soltius's user avatar
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Fingerprint enhancement lighter version

I've been advised to ask here, I hope that it fits. Original question: I want to create a more straightforward and lighter version of this fantastic repo (which itself is based on Fingerprint Image ...
RedYoel's user avatar
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4 votes
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OpenCV face recognition: Finding a best match

I am working on OpenCV2.4.2 C++ interface for face recognition functionality. The face recognition feature seems to be working fine on standard databases. (AT&T, Face Recognition Data, University ...
Trupti's user avatar
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4 votes
1 answer
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Finding Homography Matrix Using Lines

I have some Points and Lines from original image and the corresponding points and lines from top view image. -> I tried to find homography using points Used OpenCV function findHomography(...
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3 votes
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Overall approach for building a footfall/age/gender counter using CCTV footage

I would like some advice to validate my approach for building a computer vision system. Design brief: Using existing CCTV cameras in a retail store, detect the footfall in the shop (count individual ...
rosall's user avatar
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3 votes
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812 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 ...
Nitron_707's user avatar
3 votes
0 answers
889 views

Optimal measurement model for Kalman in Augmented Reality

I am developing an augmented reality SDK that uses Kalman for tracking a planar marker. My state is composed of 3D position, a quaternion, velocity and angular velocity. \begin{bmatrix}{\vec{p}}\\{\...
Jav_Rock's user avatar
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3 votes
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How should calibration points be distributed?

I do camera calibration for a single camera with a chessboard pattern in opencv for the first time. The focus is fixed. I'm not sure how to do it, there seems to be many questions: How many images ...
null's user avatar
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2 votes
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58 views

How to achieve uniform gaussian profile? Beam profile has grainy/multimode pattern

Hi apologies in advance if this (optics & image-process) is not where I should post this question. Thanks for the help! I'm required to make a jig that measures the divergence angle of a ...
Hazman's user avatar
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Taylor series approximation in Harris corner detection

While watching through the computer vision lecture on interest point detection, computing $E(u,v)$ requires computing the quantity $$E(u,v) = \sum_{x,y}(I(x+u,y+v) - I(x,y))^2$$ In the lecture, $I(x+u,...
calveeen's user avatar
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How to find location of minimum dimension of contour using opencv?

suppose this is our input image and now we have to detect the point of minimum dimension, which I show as the red dot in an output image
Akshay Kumawat's user avatar
2 votes
0 answers
270 views

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 ...
Georgy's user avatar
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405 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 ...
Shraddheya Shendre's user avatar
2 votes
2 answers
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Binarization of image for varying background and foreground colors for OCR

I am trying to develop an automated OCR system for images obtained from the internet. The images mostly consist of computer generated text imposed on a background, so the OCR should produce near ...
ntrstd11's user avatar
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Implementing a 2d butterworth filter for image processing?

I am at the moment trying to implement a bandpass butter worth filter which i then can use to apply on my original image. Problem is though My implementation of it using OpenCV doesn't seem to be ...
Bob Burt's user avatar
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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 ...
user10861's user avatar
2 votes
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122 views

High triangulation error

I have implemented a 2D->3D point triangulation method, which uses 2 poses P1 and P2 and 2 points back-projected to z=1 point1 and point2 to recover depth: ...
aledalgrande's user avatar
2 votes
0 answers
2k views

MPEG-7 descriptors' implementation in OpenCV

I'm looking for implementation of MPEG-7 descriptors which are compatible with OpenCV's recent versions and containing "region-based shape descriptor ART(Angular Radial Transformation)". I ...
γιάννης's user avatar
2 votes
0 answers
484 views

Motion and Distortion Estimation using multiple still images?

TL/DR: I'd like to take the median of lots of images to make a single "better" image. The problem is, the camera is slowly moving, and there is significant lens distortion. On the plus side the ...
Benjamin H's user avatar
2 votes
0 answers
793 views

Why do object-boundaries look better on a badly rectified image?(openCV stereo correspondence)

I got 2 pictures which is almost parallel, and not positioned very far from each other. I'm using OpenCV to try to create a disparity map (Stereo correspondence). Because I'm trying to use it in a ...
Henrik Kjus Alstad's user avatar
2 votes
0 answers
1k views

How to recognize a zebra crossing from top view using OpenCV?

How to recognize a zebra crossing from top view using OpenCV? It is not a straight zebra crossing - it has some twists and turns. I have some ideas: parallel line detection, but the available ...
user1929880's user avatar
2 votes
0 answers
470 views

STASM or AAM which is more efficient

I am working in face detection and recognition project. I am using STASM for face detction and locating face landmarks. On googling I found AAM (Active Appearance Model) and found that it is also used ...
user1317084's user avatar
2 votes
0 answers
1k views

OpenCV detecting elbow

I have to detect my elbow. I'm able to produce an image in which I'm facing the camera, standing before it and my arms are in my body plane(body plane is plane containing my head,chest,and legs)(i.e. ...
Roney Island's user avatar
1 vote
0 answers
60 views

Combining Two Grayscale Images Without Overlapping Using OpenCV and Matplotlib in Python

I am working on a project where I have two grayscale images of different sizes, named part1 and part2. Each image has some ...
Estiven's user avatar
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1 vote
0 answers
477 views

2D Deconvolution using a non-gaussian mask using C++

I am currently working on a project, where we record an electron beam profile using a target. The obtained image is a result of convolution of the actual beam profile and the aperture wherein the ...
user3198929's user avatar
1 vote
0 answers
229 views

What is the order of the output of HoughCircles in OpenCV, when having several circles on a frame?

So I am trying to use stereo vision to calculate the depth of several red balls. With the function HoughCircles, I get an output at one frame from one of the cameras like for example: ...
Faiza Ali's user avatar
1 vote
0 answers
230 views

Fisheye Lens Calibration for precision

OpenCV library offers a fisheye calibration method. I have looked at the code and looked at some papers and still don't understand how it works completely. The reason why I am interested is following: ...
Sadikov's user avatar
1 vote
0 answers
40 views

Finding defects in wall paint (finding difference in textures)

I have been experimenting with computer vision techniques to find defects in paintings, more specifically defective brush strokes. I have tried a handful of techniques such as different filters, One ...
Bikram B.'s user avatar
1 vote
0 answers
42 views

Size filtering on binary images

I have noisy images from which I extract the contours using OpencCV's findCountours, which performs binarization internally. This results in innumerable small ...
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1 vote
0 answers
46 views

KLT tracker, reject tracked occluded points

I want to use KLT tracker for a visual odometry application. Thus, I only want to track object features. Currently I'm using OpenCV's implementation ...
L_vis Root's user avatar
1 vote
0 answers
100 views

Implementing Edge Preserving Diffusion (Anisotropic Diffusion)

I am trying to implement edge preserving diffusion. Recall the general diffusion equation to be: $$\DeclareMathOperator{\Div}{div}\delta_t u = \Div(g \nabla u)$$ Where $g$ is the speed of the ...
jlcv's user avatar
  • 111
1 vote
0 answers
197 views

Pattern recognition

I am new to the world of computer vision, so please excuse my basic questions. I have two patterns: one consisting of a single circle of radius $r$, and one made of several circles, still of radius $...
Frusciante89's user avatar
1 vote
0 answers
149 views

Obtaining Subpixel Resolution for Video Processing in Python

I am working on a video processing application to calculate distance between two points using opencv Specs : Linear Pixels - 1600. FOV - 100 mm Resolution per pixel using above data : 62 micron ...
Gaurang Deshpande's user avatar
1 vote
0 answers
403 views

OpenCV denoising a 3x3 pixel pattern noise

This picture shows two photos captured by a camera from a black photographic paper. The cross is marked by laser. The left one shows a 9 pixel pattern of noise. This gets in the way of auto-focus ...
ricecakebear's user avatar
1 vote
0 answers
1k views

Line Detection with OpenCV

I'm trying to use the native functions of OpenCV HoughLines and HoughLinesP to detect the lines from an image. The Canny edge output of that image is the folllowing: The problem is that the OpenCV ...
0RI0N's user avatar
  • 11
1 vote
0 answers
91 views

Anti tremor motion detection

I'm programming in c# using opencv (emguCV). I use motion detection approach to detect some changes in a paper wall. For example it's may be colored by a laser pointer. My problem is that when I use ...
Babak.Abad's user avatar
1 vote
0 answers
61 views

How to use Mikolajczyk evaluation for detectors/descriptors?

I want to compare different detectors/descriptors (both binaries and not) for my application and I want to use the Mikolajczyk evaluation framework, which is became a standard in the community about ...
user6321's user avatar
  • 111
1 vote
0 answers
48 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. ...
Albert Garcias Mirabent's user avatar
1 vote
3 answers
244 views

Hand Jitter Problem

I am currently developing algorithm using openCV C++ for implementing laser as a mouse.Currently am having an issue of hand jitters.(ie. The presenter's hand may shake unnecessarily which may cause ...
vairav's user avatar
  • 111
1 vote
0 answers
1k views

Why correlation coefficient template matching perfoms better than cross-correlation and square-differences method

I am using this template in OpenCv's match template function by converting all images to grayscale. Here are my result using sum of square differences,cross correlation and correlation coefficient....
Muhammet Ali Asan's user avatar
1 vote
0 answers
1k views

Opencv circle detection android

Goodmorning, I have to do a circle detection with android studio using opencv, i follow the example find in internet but it didn't work and i don't understand why, i'm new of android. Can someone help ...
user3231800's user avatar
1 vote
0 answers
957 views

Visual regression test - Extract elements of GUI-Screenshot - MSER OpenCV

For a visual regression test I need to compare screenshots of webpages (different release-versions). I started with pixel by pixel compare. Actually I split the screenshot in different parts (maybe ...
MRae's user avatar
  • 111
1 vote
0 answers
321 views

Separating similiar object in an image

I have posted a question on Stackoverflow and was suggested to post here. Please refer this question for the images: Similar Question: I have used SURF Keypoints and a FLANN Based matcher and ...
Colenso Castellino's user avatar
1 vote
1 answer
218 views

How to categorize the images based on Illumination / shadow?

Input: Cropped face or Non Cropped face images. Detailed explanation: My project is face authentication. I am using OpenCV face detector to crop face from images. I am using OpenCV implementation of ...
user1317084's user avatar
1 vote
1 answer
63 views

Is the behaviour of the following filter plausible?

I've designed a filter based on this equation $$ E(u) = \frac{1}{2}\int_{\Omega} \left[(u-f)^2 + g(\lVert \nabla u \rVert)\right]dxdy $$ Euler-Lagrange equations in this case are (should be) given ...
user8469759's user avatar
1 vote
1 answer
113 views

Detecting blobs that connects to any other blob, maybe with OpenCV

In the image, I connects to universe, but II and III not. I need to detect both II and III, also I if possible. Is it possible with current computer vision libraries?
merveotesi's user avatar
0 votes
0 answers
26 views

Is feature matching useful on full Mahjong set?

I am trying to identify every riichi mahjong tiles in one hand. I am using OpenCV (on android) and currently I tried ORB and SIFT but even if SIFT had better result its far from usable. I only try to ...
rXp's user avatar
  • 101
0 votes
0 answers
123 views

Removing dense grid lines & convert into clear image - opencv - python

I want to extract the text from this image. I'm a newbie in opencv. I've tried various opencv codes across various questions, but none is working for me. How can I extract text from this? Or maybe ...
Pankaj Singhal's user avatar
0 votes
0 answers
18 views

Edge-preserving Image Stacking Method

I have been working on restoring some old stereographic images. This means I have a Left and Right image of effectively the same thing with different elements of wear on the image for each side. I had ...
user3046771's user avatar