Questions tagged [opencv]
OpenCV (Open Source Computer Vision) is a cross-platform library of programming functions for real time computer vision.
77
questions with no upvoted or accepted answers
9
votes
0
answers
1k
views
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 ...
- 201
5
votes
0
answers
1k
views
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 ...
- 163
4
votes
0
answers
1k
views
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 ...
- 41
4
votes
1
answer
538
views
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(...
- 41
3
votes
1
answer
65
views
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 ...
- 131
3
votes
0
answers
78
views
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 ...
- 31
3
votes
0
answers
811
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 ...
- 131
3
votes
0
answers
885
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}}\\{\...
- 1,213
3
votes
1
answer
260
views
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 ...
- 252
2
votes
0
answers
39
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 ...
- 21
2
votes
0
answers
140
views
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,...
- 283
2
votes
0
answers
49
views
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
2
votes
0
answers
268
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 ...
- 133
2
votes
0
answers
398
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 ...
2
votes
1
answer
2k
views
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 ...
- 121
2
votes
0
answers
2k
views
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 ...
- 359
2
votes
1
answer
97
views
Primitive Feature Detection to Detect a Black Circle within an Image
I am trying to check whether this black circle is exist or not on my images.
My current approach is like that;
Hough Circle detection
Crop the outer roi
Adaptive threshold
count zero pixels
if ...
- 257
2
votes
0
answers
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 ...
- 21
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 ...
- 43
2
votes
0
answers
481
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 ...
- 131
2
votes
0
answers
789
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 ...
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 ...
- 21
2
votes
0
answers
469
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 ...
- 365
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. ...
- 453
1
vote
0
answers
100
views
Segment Hand Image into Palm and Fingers
Here is my code, i want to extract only the fingers and save them as a new image
...
- 11
1
vote
0
answers
430
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 ...
- 11
1
vote
0
answers
217
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:
...
- 11
1
vote
0
answers
203
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:
...
- 9
1
vote
0
answers
37
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 ...
- 11
1
vote
0
answers
38
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 ...
user7657
1
vote
0
answers
43
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 ...
- 11
1
vote
0
answers
97
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 ...
- 111
1
vote
0
answers
193
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 $...
- 11
1
vote
0
answers
147
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
...
1
vote
0
answers
388
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 ...
- 111
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 ...
- 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 ...
- 146
1
vote
0
answers
60
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 ...
- 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. ...
1
vote
2
answers
212
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 ...
- 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....
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 ...
- 11
1
vote
0
answers
119
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:
...
- 237
1
vote
0
answers
935
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 ...
- 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 ...
1
vote
1
answer
214
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 ...
- 365
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 ...
- 395
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?
- 111
0
votes
0
answers
16
views
Python - CV, contour and measurements
I have small problem with cv in Python and rhombus. I can read frame from the camera and create contours...
...
0
votes
0
answers
27
views
PSNR decreases while denoising
I currently am trying to portray PSNR's ability to measure noise in an image. The PSNR is said to be high (around 40 dB) if there is a low amount of noise in the 2D signal.
In my experiment I have ...
- 1