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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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0 votes
2 answers
13k views

Bit plane slicing in Python

I recently came across a technique called bit-plane slicing for image compression in a book "Digital image processing" by Gonzalez and Woods. They just presented the theory and I wanted to ...
2 votes
3 answers
90 views

What is the type of blurring in such an image?

I can't figure out what type of blur such an image has and how I would be able to generate it in python. I would be grateful for any help. I tried Gaussian blur, bokeh blur, Wolf and Born out of focus ...
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 ...
1 vote
2 answers
271 views

How to remove dark shadows from camera capturing when combining LED spots and ambient light

I'm getting strange moving shadow strips on my camera capture during a computer vision experiment: As the gif image above shows, those strips move to bottom slowly. I have also noticed that it ...
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 ...
4 votes
1 answer
80 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 ...
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 ...
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 ...
2 votes
2 answers
164 views

Camera sensor artifacts next to edges in calibration images; what is causing these?

I am trying to image some ChArUco targets using a monochrome machine vision camera with a CMOS sensor and the attached images show the artifact I am observing: 2-pixel-wide bright vertical streaks ...
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 ...
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 ...
25 votes
6 answers
37k views

How do I get the most accurate camera calibration?

First off, I hope this is the correct Stack Exchange board. My apologies if it is not. I am working on something that requires me to calibrate the camera. I have successfully implemented the code to ...
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 ...
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 ...
13 votes
5 answers
5k views

Slicing and Recognition of book title and author from bookshelf image

I am trying, for my own learning purposes, to develop an implementation of an algorithm that would list books, given an image of a bookshelf like the following: The first step is to slice the image ...
1 vote
1 answer
140 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 ...
1 vote
2 answers
4k views

OpenCV warpPerspective implementation

I've implemented the least squares method to find the homomorphic image to fix the rotation and projection in an image. Now I'm trying to implement the OpenCV warpPerspective method in order to "...
0 votes
0 answers
79 views

Detect GUI Buttons in every application window with python

I want to detect every buttons in every application windows. For example, in explorer window, I want to detect every Tags, folders, files and Buttons like "page back", "page forward&...
0 votes
0 answers
31 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
65 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 ...
4 votes
3 answers
1k views

Detecting bullet holes using Python with camera or sensors

I am trying to build a system to detect bullet holes in paper. I've read many StackOverflow threads but not a single one satisfied me. Current methods, which I am using, are good but not perfect and ...
1 vote
1 answer
351 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:...
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 ...
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 ...
3 votes
1 answer
221 views

Shape Properties Which Are Scale Rotation Invariant Like HuMoment

There are other shape properties scale-rotation invariant except HuMoment? There are example that show me how can i implement them? I find this example in c++ https://stackoverflow.com/questions/...
2 votes
1 answer
683 views

How can i compute perimeter and area of a skeletonized circle?

In opencv if i use findcontours function, i get contours and i can compute area, perimeter, convex hull. if i use a Skeletonized image of a circle how can i compute perimeter,area, convex hull of the ...
1 vote
1 answer
769 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 ...
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 ...
0 votes
1 answer
502 views

Finding rectangle corners by using point cloud

I have a rectangle in the 3D scene, which I know its width and height. It is placed in the 3D scene like the image below. I can manually select all points on the rectangle by mouse click. Given the ...
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... ...
0 votes
1 answer
280 views

Python - Find the coordinates of the point at the tail of the fish

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0 votes
0 answers
27 views

How to detect a line from a broken line segment in video?

I am trying to detect meteors in a video, and so far, what I did. Preprocessing: changing to grayscale and morphological operations like dilation and erosion. background subtraction method adding ...
4 votes
1 answer
760 views

OpenCV 2 Connect Incomplete Contours edges

I have to connect the unfinished edges of the contours in the red color bounding box. I used distance transform, watershed, and morphology, but still, edges are not connecting. ...
2 votes
1 answer
758 views

Gap Filling Contours / Lines

I have the following image: and I would like to fill in its contours (i.e. I would like to gap fill the lines in this image). I have tried a morphological closing, but using a rectangular kernel of ...
2 votes
1 answer
171 views

Looking for a way to fill holes in objects, and break bridges between them

I am trying to extract building footprints from satellite images. Using a series of morphological operations i.e erosion and opening by reconstruction, I'm able to obtain the footprints, albeit with a ...
0 votes
1 answer
737 views

Laplacian Filter kernel size meaning

I'm using laplacian filter in opencv. I usually use laplacian filter with kernel size 3 which is default setting in opencv. I'm just curious what happen(intuitively) when I choose bigger size kernel? ...
2 votes
1 answer
401 views

Can DFT magnitude be used to identify repeating patterns in an Image?

Given the DFT magnitude vector of an 1-D image, I want to understand if we can calculate the size and pitch of repeating patterns in the image. Is this possible? I took a few test images and ...
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 ...
2 votes
1 answer
2k views

Implementation of Wiener filter to deblur an image using Python and OpenCV

EDIT: I have debugged the runtime warning, and now I am able to get an output image. However, the output image is still blurry. Increasing the constant value heavily distorts the image. Setting ...
3 votes
1 answer
3k views

Removing white reflective pixels from scanned RGB image (Python - preferably OpenCV)

The images above are tiles taken from a scanned painting. It's easy to see where there are tiny reflections scattered throughout. I wish to remove (or diminish) the tiny reflections somehow, across a ...
9 votes
3 answers
44k views

Removing noisy lines from image - opencv - python

I want to process different type of image to extract actual text from noisy image .I am using open cv to do this job it is working fine but the problem is I need to set different lower threshold to ...
1 vote
1 answer
381 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 ...
3 votes
2 answers
367 views

Which Blur is being used in this effect

I'm trying to recreate an effect used on photoshop called satin effect, which has an option that control the size of the satin, which I think it's just a special blur applied to the satin pattern So ...
2 votes
2 answers
382 views

What happens when you read and save the same JPEG image again over and over?

This question is mostly related to jpeg compression and expected results when you read and save the same jpeg file several times. Let's say you have read an uncompressed image (originally it has never ...
5 votes
2 answers
1k views

What Is the Best Color Space to Work with for Hand Detection: RGB, HSV, or YCrCb?

I'm working on hand gesture recognition using C#. I'm using OPENCV for skin detection but its performance is not optimal. So I decided to do some filtering based on color space, but I do not know what ...
1 vote
2 answers
742 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 ...
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 ...
3 votes
1 answer
2k views

How can I detect pipeline cracks using OpenCV and Python?

I have developed a robot that captures images of the pipeline interior as it moves. The requirement was to be able to detect cracks inside. So far i tried several OpenCV codes that find the crack ...
23 votes
3 answers
43k views

What Is the Difference between Difference of Gaussian, Laplace of Gaussian, and Mexican Hat Wavelet?

There are three techniques used in CV that seem very similar to each other, but with subtle differences: Laplacian of Gaussian: $\nabla^2\left[g(x,y,t)\ast f(x,y)\right]$ Difference of Gaussians: $ \...
4 votes
1 answer
638 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(...

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