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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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&...
roy's user avatar
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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... ...
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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 ...
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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 ...
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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. ...
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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? ...
Hyun Bin CHo's user avatar
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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 ...
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OpenCV canny vs my own C++ version - high difference

I have implemented my own canny edge detector in C++. If I compare the result with the same thresholds to OpenCV (cv::Canny(img, res, 50, 100)), the difference is ...
Martin Perry's user avatar
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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 ...
cppcoder'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 ...
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Python - Find the coordinates of the point at the tail of the fish

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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
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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 ...
underdawg631's user avatar
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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 ...
Konchog's user avatar
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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 ...
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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 ...
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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 ...
SaulGoodMan's user avatar
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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 ...
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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 ...
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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:...
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3 answers
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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 ...
Rafał Hrabia's user avatar
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How can I segment areas, each of which has nearly same colors of pixels in an image?

For clarity, Nearly same colors of pixels belong to a category. Another nearly same colors of pixels belong to another category. The distinction depends on nearly same RGB values of pixels.
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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 ...
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Feature Extraction for Image Classification of Vegetables and Fruits Using Classic Computer Vision Techniques

I don't know if this is the right place to ask this but lets go. I am a beginner in computer vision and I have a project of fruit recognition based on Kaggle's Fruit 360 dataset. I know that CNNs are ...
Manveru's user avatar
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bilateral filter for color images

Fast Bilateral Filter I came across the above code of the bilateral filter for grayscale images. I tried to implement it for color images by splitting the image ti BGR channels and applying it to each ...
Ananya Agarwal's user avatar
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682 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
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263 views

Find vertical/horizontal lines

I tried everything including the Hough Transform with different inputs; Laplacian and Sobel and Canny edge detector were run on filtered image but cv2.HoughLinesP and cv2.HoughLines both give me wrong ...
Alex's user avatar
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OpenCV: Can't find large rectangle contour

I'm trying to re-create the dimensions of an object by setting it up on a grid and taking as close to a top-down photo I can which I will then get the contours of the largest bounding rectangle and ...
astroturfdurf's user avatar
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Is there a way to find the contours of instances in a binary mask image by color?

I need to find the contours for each of the instances of microscopic cells in a binary image mask of dimensions 256 x 256 shown below. My approach involves thresholding the image to get a binary mask ...
Nolan Cardozo's user avatar
1 vote
1 answer
263 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 ...
Duloren's user avatar
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1 answer
330 views

How to detect rectangular images inserted into another image?

It's just for a simple binary classification, so it's not needed to find the location of the inserted image or the content. I'm only interested in checking whether something like that is present or ...
Tobias Hermann's user avatar
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1 answer
485 views

How to Remove Double Lines Detected Along the Edges by Edge Detector?

I'm trying to take real time input for hand gestures with web cam, then processing the images to feed them to a neural network. I wrote this processing function to make the hand features look ...
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image processing find liquid level (only with images processing, no AI)

I want some ideas to get the level of a water/liquor in a cup. i tried many ideas (contours, edges,...) but nothings is working. So any ideas that i can explore.
Moooooooun's user avatar
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Morphological operations to isolate and preserve network graph structure?

Suppose there is an image with long, connected lines which form connected, closed cycles in an image. Is there a standard morphological approach to isolate only the lines, and drop all other pixels? ...
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What is the function of init in Active Contour Model

In practice of image processing using scikit-image, I didn't understand the role of constructing init numpy array in Active Contour Model example. Is it the red section drawn in the example astronaut ...
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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
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1 answer
120 views

Suggestions for creating 3D Bounding Boxes of Books on a Shelf from RGB-D Images

I am new to image processing, so I beg your pardon if this is a trivial question. I am trying to use an RGB-D camera to detect 3D bounding boxes of books on a shelf. Here are some examples of possible ...
Dhindhimathai's user avatar
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106 views

Find camera tilt

If I have a camera that captures tilted images what is the way to find the tilt of the camera? Is there a pattern that I can photograph or something similar. I want to reduce the tilt as precisely as ...
Sadikov's user avatar
2 votes
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146 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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Harris corner detection shape of $E(u,v)$

I am taking a computer vision class and I have just learnt about the Harris corner detection concept. A corner is detected when a small shift in a window function defined around the corner results in ...
calveeen's user avatar
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513 views

Extracting articles from epaper into individually cropped image

I want to segment the image below (click for bigger image) into columns based on the natural gaps that exist in the columns. The article columns should be perfectly vertical and need not be the same ...
Shashwat Shankar's user avatar
1 vote
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222 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
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215 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
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2k views

How can i get Celsius/kelvin temperature from a thermal image in python language?

How can I convert RGB values of the thermal image into Celsius or kelvin temperature in python? Here is the thermal image taken by a FLIR device: Here I am reading image using OpenCV and getting the ...
rizwan's user avatar
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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 ...
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Low samples numbers machine vision training for object detection

I'm trying to set-up a machine vision application in which I have to detect the position of a printing nozzle (in the red sqaure in the image) in a field of view in order to prcisely position a ganty ...
EvilGarfield's user avatar
3 votes
2 answers
723 views

what is the difference between the convolution and differentiation over image in image processing?

In image processing the differentiation and convolution are the terms that are used interchangeably. What is the difference between applying convolution and differentiation over the image? How we ...
vignesh babu's user avatar
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1 answer
1k views

Why we have to multiply the images with $(-1)^{x+y}$ to center the transform in frequency domain filtering?

To perform the filtering infrequency domain we perform multiplication of $(-1)^{x+y}$ why??
vignesh babu's user avatar
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1 answer
944 views

How the Grayscale images are converted back to RGB?

In case of RGB to grayscale conversion we take the average of R,G,B channels and convert them to Grayscale which has songle channel. How to convert back the Grayscale to RGB ??
vignesh babu's user avatar
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259 views

Use sparse optical tracking to track a Bounding Box object

I need some help on solving this issue. Any tips are appreciated. The goal of the project is to try to track a Bounding Box object, chosen arbitrarily in an image, throughout many frames of a ...
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