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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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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 ...
Jack Simpson's user avatar
2 votes
1 answer
104 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 ...
Anar Bayramov's user avatar
2 votes
1 answer
508 views

Efficient Hessian-Laplace blob detector implementation

As it is mentioned in a paper for SURF, it is possible to approximate hessian determinant using integral images. If I want to implement Hessian-Laplace detector, is it feasible to also approximate ...
warmspringwinds's user avatar
2 votes
1 answer
5k views

Zernike Moments' implementation in OpenCV

The reason why Hu moments were implemented in OpenCV and why Zernike moments were not implemented is looking like their performance similar as stated in this paper. As stated in the paper Zernike ...
γιάννης's user avatar
2 votes
1 answer
1k views

How to get more accurate results with OpenCV

I would like to ask about this function in OpenCV: cvTermCriteria( CV_TERMCRIT_ITER | CV_TERMCRIT_EPS, 20, .3 ) How do I get more accurate results - do I need ...
seereen's user avatar
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2 votes
1 answer
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Texture mapping on a 3D face from 2D face image

I have 3D points (xyz) of a face image and I have 2D face image of the same person. The 3D points of the face are such that If I project the points to 2D plane, it matches with the 2D face image. I ...
face's user avatar
  • 121
2 votes
0 answers
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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2 votes
0 answers
155 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,...
calveeen's user avatar
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0 answers
50 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
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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2 votes
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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
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 ...
ntrstd11's user avatar
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2 votes
2 answers
7k views

Blending artifacts in OpenCV image stitching

I am using OpenCV to blend a set of pre-warped images. As input I have some 4-channel images (*.png or *.tif) from where I can extract a bgr image and an alpha mask with the region related to the ...
Finfa811's user avatar
  • 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 ...
Bob Burt's user avatar
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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 ...
user10861's user avatar
2 votes
0 answers
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
4k views

Need help in panoramic image stitching using emgu cv [closed]

I am doing a project on panoramic stitching of Images using Emgu CV (Open CV for C#). Till now I have done some work that stitches images but the output is kinda weird. This is what I am getting: My ...
gitter's user avatar
  • 121
2 votes
2 answers
7k views

OpenCV: Problem at creating a Skeleton of Lines

I need to get the lines from a photographie of a sheet of paper. While recherching, I came along this, where one answer referred to this blog entry. Now I am having trouble with this approach. I have ...
BlackMamba's user avatar
2 votes
2 answers
1k views

Object-Recognition using SIFT: Switching the order of images creates two different results

I've developed a large test-system which can use every interest-point-detector and -descriptor. I use it for evaluation of the given algorithms with the standford-image-collection of cd-covers. This ...
Mr.Mountain'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
3 answers
1k views

Image processing, recognizing a small feature in a larger image

I am trying to write an image processing program to recognize bubbles in oil. It has been suggested I try computing the convolution of the image and an image of a typical bubble. i.e. : ifft(fft(a)....
sav's user avatar
  • 425
1 vote
2 answers
80 views

Camera image pixel structure origin

I am using machine vision for industry task with opencv. I have images from a camera monitoring the process. The detailed look at the small part of the image follows: Enlarged: In the detail, it ...
matousc's user avatar
  • 667
1 vote
2 answers
1k views

texture matching between patches of an image

I have an image A which I have divided into 4 x 4 subband images. For a given patch P1 in ...
kunal18's user avatar
  • 75
1 vote
2 answers
13k views

Running the BM3D Denoising Algorithm in Python

I am looking for a strong baseline in image denoising and therefore wanted to have the BM3D algorithm in my benchmark. These 2 python implementations: https://github.com/ericmjonas/pybm3d https://...
Zaccharie Ramzi's user avatar
1 vote
1 answer
4k views

How to detach overlapping contours but not to remove small ones. Alternative to erosion-dilation cycle

Background: I'm trying to detect trees on a sequence of aerial images by calculating a stereo disparity for consequent pairs of images. This is how disparity looks like. White spots are trees: Next, ...
Georgy's user avatar
  • 133
1 vote
1 answer
8k views

How can I construct a Band-pass filter from a low and a high-pass filter?

Suppose, I need to construct a Band-pass filter in OpenCV. But, I know, there are no functions in OpenCV for Band-pass filters. Now, what I need to do is to have a low-pass filter and a high-pass ...
user avatar
1 vote
2 answers
2k views

Finding the Harmonics contained in an Image?

I am beginer in image processing. Any signal whether it is 1D,2D or any multidimensional signal can be represented using combination of number of sine and cosine wavesforms (harmonics). Similerly any ...
devraj's user avatar
  • 407
1 vote
2 answers
3k views

Image processing (number recognition) woes

So I have the following image: Using GIMP, I was able to get to here: Select all white color (with a touch of fuzz) Invert selection Cut selection Invert all color (goes black) But now I'm stuck... ...
Eamorr's user avatar
  • 111
1 vote
2 answers
3k views

Improve contrast when image has a flood of white balancing

I have an image taken a night time. I apply _EqualizeHist to it. But the result is a high level of whiteness running through the image. This is the image: I had asked this question in a slightly ...
Andrew Simpson's user avatar
1 vote
2 answers
12k views

How to Compute Image Gradients?

How to compute Image gradients? In X Direction - Kernel : -1 0 1 In Y Direction - Kernel : -1 0 1 Let's assume my input image is: unsigned char* imgImage; ...
Pixel's user avatar
  • 21
1 vote
1 answer
2k views

Image processing functions for quality control

I have to use image processing for quality control of a cookie manufacturer (as a part of my project). The program must be able to detect oversized, undersized, distorted cookies, cookies having ...
Manyu Deshpande's user avatar
1 vote
1 answer
397 views

Problem with "Topological Structural Analysis of Digitized Binary Images by Border Following" by Suzuki Abe

I have a Problem with the Paper "Topological Structural Analysis of Digitized Binary Images by Border Following" by Suzuki and Abe. In the Chapter "Appendix I: The Formal Description of ...
Vanior's user avatar
  • 11
1 vote
2 answers
747 views

Calibration using Camera Calibration Toolbox for Matlab vs OpenCV

I am currently working to calibrate a camera and I tried using both the Caltech Camera Calibration Toolbox for Matlab and OpenCV. I used the same images for both methods. Even if the error seems to ...
Otter_warrior's user avatar
1 vote
1 answer
705 views

How do I detect the sharp edges in the following image?

I am looking to count the sharp pointy triangular things in the image. However I was unable to do so. One approach I did try was take a convex hull of the contour and then find convex defects but it ...
AJAY G's user avatar
  • 31
1 vote
1 answer
636 views

Signal in frequency domain with OpenCV dft

I am experimenting with cv::dft: a 1HZ sinus signal is generated, and displayed in the frequency domain. But for some reason it hasn't got the maximum component at ...
Dániel Terbe's user avatar
1 vote
1 answer
771 views

Convex Hull Area in Pixels

I am calculating different attributes for connected regions of the image, with the final goal of classification. One of the attributes I am working with is a sparsity measure, calculated as the ratio ...
penelope's user avatar
  • 3,676
1 vote
1 answer
10k views

How to calculate the luminance of an image?

Is there any method for calculating luminance of an image? As from wiki got to know Luminance is an amount of energy perceived by the observer and LUX is different from brightness. But still is ...
user3805574's user avatar
1 vote
2 answers
6k views

Skew detection and correction using Fourier transform

I was trying to implement skew correction method for scanned documents using the method described in this paper. The algorithm steps: 1- Threshold the image . 2- Find the fourier transform. 3- ...
Ibrahim Amer's user avatar
1 vote
1 answer
7k views

DFT and Inverse DFT in Image Processing

I have implemented DFT from Vision & Graphics Group at the Faculty of Informatics and Information Technologies STU - Frequency domain filtration. Tried taking dft for the three Channels(R, G and ...
OpenCV User's user avatar
1 vote
1 answer
7k views

OpenCV Motion Analysis: Optical Flow vs Motion History

OpenCV Motion Analysis Documentation lists multiple techniques for motion tracking: Sparse Optical Flow | calcOpticalFlowPyrLK, Dense Optical Flow | calcOpticalFlowFarneback, and Motion History ...
Manav Kataria's user avatar
1 vote
2 answers
514 views

Grayscale conversion before applying sobel gradient operator

I am currently replacing a hand-made image processing library by OpenCV. The programmer who worked on this library had implemented the sobel gradient function. This implementation is right except that ...
MarAja's user avatar
  • 133
1 vote
1 answer
2k views

How to adjust reverse range for Hue in cvInRangeS?

cvInRangeS method for HSV colorspace is used like: ...
Gürcan Kavakçı's user avatar
1 vote
1 answer
84 views

FaceAuthentication

My project is Face Authentication. System Description: My input is only one image (which was taken when the user logins for the first time) and using that image system should authenticate whenever ...
user1317084's user avatar
1 vote
1 answer
141 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 ...
Paul Daniels's user avatar
1 vote
1 answer
355 views

What does the last row of a homography matrix mean?

I have used the MOTION_HOMOGRAPHY function in OpenCV (python3.6, enhanced correlation coefficient) to register a pair of images, and I am trying to interpret the 3 x 3 warp matrix the function returns:...
T Walker's user avatar
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