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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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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Stitching images with common "static" element using OpenCV

I need to stitch images from the camera attached to the robotic arm. OpenCV has a nice feature (Stitcher), though it's not working correctly, as there is one static element (in the same position on ...
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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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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 ...
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OpenCv: Homography transformation with perspectiveTransform results in strange data

I am trying to use SIFT to match a template in a scene image (to find an object). For most of my test data my algorithm works pretty well, but for a specific one, it doesn't. I am not completely sure ...
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How to do stretching Image distortion transformation

I have an assignment to transform an image like this: I have done with twirling, fisheye, bulge, but I'm having a hard time finding the right formulas for those effects. here is my code for twirling: ...
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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 ...
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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 ...
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Parameter tuning for noise removal in video frames background subtraction

I’m working on motion detection using video frames background subtraction. I already reached a good result by filtering detected motions area using thresholds where I keep only reasonable motions by ...
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Image Z Coordinate Clarification

I'm trying to understand 3D image reconstruction, and want to clarify how we can find a z image coordinate. Is the z coordinate for image coordinates (x,y,z) the focal length since that's the distance ...
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How to improve accuracy of camera extrinsics calibration

I have a multi-camera system where the field of views are mostly non-overlapping. I have been researching on methods to calibrate the camera extrinsics and the first thing I'm going to try is to take ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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.
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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 ...
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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 ...
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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 ...
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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,...
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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 ...
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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 ...
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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: ...
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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: ...
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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 ...
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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 ...
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3 votes
2 answers
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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 ...
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1 answer
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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??
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1 answer
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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 ??
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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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Calibrating cameras with different resolutions

I have two cameras with very different resolutions. One camera is the RGB camera of the microsoft kinect sensor with a resolution of 1920x1080 and the other one is ...
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Salt and Pepper impulse Denoising opencv

I am creating a generic method to work on salt and pepper noise and variants. The example images are as shown below : I tried few methods, such as ...
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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 ...
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Finding point height on a cup using OpenCV

Suppose that I want to find the 3D position of a cup with its rotation, with image input like this (this cup can be rotated to point in any direction): Given that I have a bunch of 2D points ...
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How to find position, scale and rotation of a known shape/contour in an image?

I have an image of an object. The image shows a high contrast outline of the object. It is guaranteed that the image shows exactly one object. The shape/contour of that outline is known. It is not ...
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2 votes
1 answer
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Licence plate enhancement

Is it possible to enhance the image below and make it more readable? I have tried apply binarization but there is some kind of shadow. So I have tried to convert image to gray scale and then ...
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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
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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://...
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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 ...
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SIFT between 1 image and dataset (2 images)

I use SIFT, and I want to find the angle of inclination of an image compared to two reference images, in short: I have 3 images : Image x: input image Two images 1 and 2, reference images that are ...
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1 answer
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How to produce color image using edge detected images?

Hi I am trying to produce an image which is a combination of multiple images such as in focus stacking. Now I have 6 photos and I want to produce a final image such that the final image uses blocks of ...
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