OpenCV (Open Source Computer Vision) is a cross-platform library of programming functions for real time computer vision.

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How to get rid of ripples from a gradient image of a smoothed image?

I have a gray scale uint8 image. When I smooth it with a Gaussian filter and then compute the gradient image with a Sobel filter in OpenCV, ripples would appear. The first image is what happens when ...
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10 views

How can we know the geometry of a blob detected by OpenCV

I am performing blob analysis using connectedComponentsWithStats, which returns elementary statistics about the blobs (AABB and area). It is also possible to ...
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19 views

Practical advices for applying phase correlation in image registration task

I'm using OpenCV to detect shift between 2 images, here is sample code (based on cv::phaseCorrelate function): ...
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13 views

How to get Harris corners that are present in watershed segmented Bitwise image(road part)?

This is Harris corner image of test image: This is Bitwise watershed segmented image: I want to get that Harris corners which will be in segmented part of image(road part).
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15 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 ...
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2answers
141 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 ...
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19 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 ...
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29 views

How many types of Bandpass filters are there for image processing?

This article shows that: Ideal Bandpass filter Butterworth Bandpass filter Gaussian Bandpass filter Is that classification correct? Are there any other types?
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36 views

Poster detection in OpenCV?

I'm really new in image processing, so please sorry I'm a newbie. I tried to use the squares.cpp for detecting posters (since they usually are rectangles) without using expensive feature detectors (...
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14 views

Image retrieval approach

I have a good understanding of 'normal' Machine Learning, I'm pretty good at Python and have decided to start a Raspberry Pi project, however my knowledge of Image Retrieval is limited. I'm trying to ...
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34 views

Stereo Camera: Origin of Epipolar line is Lens or Image sensor?

In a standard Stereo camera set-up where is the Origin of Epipolar line located? whether it is at the Lens or at Image sensor? I'm using Opencv Stereo camera calibration method to calibrate my camera....
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52 views

Count the vehicles flow that pass over one bridge

I live in an apartment near a bridge. From my window I can see the cars traveling over the bridge as you can see below: Is there a relatively simple manner to count each car pass over the bridge? ...
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12 views

Drawing boxes where features in image are marked by contours

I am trying to draw boxes to surround features in images, however, I have obtained very weird results but I am not sure what has happened. The image in the window titled "drawing" is the image after ...
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31 views

How to remove noise from this image without causing the crack to 'shrink'?

I am currently embarking on an image processing project to detect cracks on surfaces using OpenCV and Visual Studio via C++. I have tried writing my program and at the moment, I am stuck because I ...
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24 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 ...
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63 views

Which pattern (circle pattern or checkerboard pattern) should be used for automotive camera calibration (fisheye/wide webcam)?

Calibrating a Fish-eye camera / webcam with large angle mounted on car by using opencv 3 One important issue is to define the calibration pattern and its position !!!! The affects error that paly an ...
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55 views

Python cv2 Image Pyramids

Trying to implement the famous Orange/Apple pyramids blending (cv2 Image Pyramids). Note: Both images shape is 307x307. However, since the result image is blurred due to clipping values in ...
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70 views

Object detection in binary image

This task comes from tracking object on a steady background. So far I was able to remove the background and obtain binary masks like this: I need to get bounding rectangle of the toy without the ...
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13 views

how to project images in different angles?

My theoretical knowledge in image processing is not all that good. I was reading a paper when I came across the following: To carry out such a comparison, we simply rotate from 0 ◦ to 180 ◦ and ...
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35 views

Finding crosses and their orientation on a given image

I want to recognize table structure from some arbitrary photo image and store it in some formal notation (Let it be HTML table notation). For example I have this blurry image as input: After ...
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35 views

How to antialias result of a distance transform?

I am using OpenCV to filter a grayscale image of defined shapes in order to get a linear interpolation of values on a specified distance starting from the edge of the shape toward the "center". ...
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32 views

Add padding to object in 4-channel image

I have a 4-channel image (.png, .tif) like this one: I am using OpenCV, and I would like to add padding of type BORDER_REFLECT around the flower. ...
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21 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. ...
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408 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 ...
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62 views

Histogram matching

I am implementing histogram matching program with 3 RGB color channel. My choice for the RGB histogram instead of HSV is only about understanding. To process this matching, I calculate 2 histograms (...
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27 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 ...
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132 views

Can I create a transformation matrix from rotation/translation vectors?

I'm trying to deskew an image that contains an element of known size. Here's a test image: I can use aruco::estimatePoseBoard which returns rotation and ...
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147 views

Improve coverage of BackgroundSubtractorMOG2 and findContours

I'm trying to track players on a soccer field, using a fixed camera. The picture below shows the results of BackgroundSubtractorMOG2, the second picture below the results of findContours on the ...
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109 views

NORM_HAMMING2 vs NORM_HAMMING

I'm trying to use ORB features with a cv::BFMatcher. ORB is based on binary descriptors so HAMMING must be the choice, but I'm not sure I understand the difference ...
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110 views

How to find the largest empty rectangle using OpenCV?

I need to find the coordinates of the largest empty rectangle in a PNG image. The rectangle should consist of light colors (if that is too difficult, white pixels only are fine) and should be axis-...
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152 views

Should I use CV_HAAR_SCALE_IMAGE while using LBP CascadeClassifier?

I trained a cascade-LBP to detect Lollipops with 1000 images, now I'm trying to "adapt" the openCV HAAR-Cascade example to use my LBP trained .xml but I'm not sure about the "HAAR_SCALE_IMAGE" flag, I ...
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42 views

What is a good way to locate butterfly in an image

I have some images of butterflies. I've downloaded them from here. A sample is below: In each image, the most prominent object is the butterfly (with flowers, leaf etc in background). I usually go ...
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963 views

Python - Normalized cross-correlation to measure similarites in 2 images

I'm trying to measure per-pixel similarities in two images (same array shape and type) using Python. In many scientific papers (like this one), normalized cross-correlation is used. Here's an image ...
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87 views

Vein extraction from this image

I have this image: What methods should I use to extract the veins from this image. Thank you.
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57 views

Can I segment characters from this image with CSV?

I am trying to segment my characters on this image with using column sum vector. This method actually works on the paper I've read about license plate recognition. it looks useful for my images ...
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39 views

Video stabilizer assessment. Estimate point spread function PSF

My goal is estimate PSF about image quality assessment of a video stabilizer c++ code from original shaked to stabilized image. I have read this abstract as road map but some point appears cumbersome ...
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47 views

Saliency Map based on itti model

i want to create a Saliency Map based on itti model via OpenCV(Python). what i'm doing is that: 1- first i change image color space from RGB to LAB color space 2- for each color channel, i create a ...
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217 views

Log-Polar DFT Based Scale-Invariant Image Registration

I'm trying to do image registration using phase correlation as described in the Reddy Chatterji paper. In my case, the images may be scaled and translated relative to each other. The algorithm for ...
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276 views

How to calculate the scale, rotation angle and translation between 2 images if we know the homography result matrix?result

I got the result of findHomorgraphy in OpenCv. As below: Homography transform matrix: [-1.1534205416542787 0.7834287271121142 527.9064589440736 -0.2415444621693116 0.16412191792642924 ...
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23 views

Getting composition of a mixture of colours

I wanted to validate a thought on blending of colours digitally. Imagine I have two colours, $C_1$ $(R_1,G_1,B_1)$ and $C_2$ $(R_2,G_2,B_2)$. Now, I create colour $C3$ as follows: $C_3 = \alpha C_1 + ...
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70 views

Photogrammetry in orthodontics

How to calculate and visualize metrics for various image properties in orthodontics? I'm looking for an objective way to enrich layman pictures in orthodontics (like jaws and the facial profile ...
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180 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....
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143 views

OpenCV's BackgroundSubtractorMOG algorithm parameters

Does anyone know what the history and number of Gaussian mixtures do in the Gaussian Mixture-based Background/Foreground Segmentation Algorithm used in OpenCV? I'm trying to optimise a background ...
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3answers
65 views

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 ...
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16 views

x shift impulse noise?

Is it possible to add some form of gain to an image, such that an impulse noise get shifted along the x-axis.. I have these two histogram of an image with noise and the original image. As you ...
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191 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 ...
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82 views

Implementing contraharmonic filter

I am at the moment trying to implement a contra harmonic filter,to remove the pepper noise from an image. But the implementation of it seems a bit incorrect, and I am not sure what is wrong. ...
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376 views

Rotated object detection by Viola jones Algorithm

In my project I need to detect rotated and non-rotated faces in real time. I read original articles and try to use common implementation in matlab and openCV. And as I understood Haar features are not ...
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744 views

How to verify if two images have the same object/content?

I am truly new to computer vision field, but it is fascinating me! I have now a challenge in my hands and I am seeking for mentors/advisers to give me some follow up. My project is: From a picture of ...
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59 views

Creating a convolution kernel from filter description

I am not quite sure whether the question I am stating is right, or if I am trying to combine two not related topics but here it comes.. I am trying implement and apply a contra harmonic mean filter, ...