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

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Find Translation, Rotation and Scale Values from Parameters of Homography Matrix

Assume that we have a homography matrix. The homography matrix looks like: I want to use homography matrix parameters for robot odometry like this paper. Bu I couldn't determine translation ...
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30 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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5 views

OpenCV: CascadeClassifier_CUDA [closed]

I'm trying to use the CascadeClassifier_CUDA type in OpenCV, but I have problems with it. The compiler says that it is not a member of cv::cuda and I don't know why, I'm getting crazy... Here's my ...
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13 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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14 views

Laser Pointer Detection

In my project I want to develop a robust Algorithm to detect laser pointer in the projected screen and my algorithm want to find it's X,Y co-ordinate.Can anyone suggest some algorithms to find laser ...
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1answer
23 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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34 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 ...
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1answer
17 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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24 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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1answer
66 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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25 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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1answer
26 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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18 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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18 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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75 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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70 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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1answer
20 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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57 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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51 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 ...
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62 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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2answers
36 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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13 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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49 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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2answers
61 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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1answer
134 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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1answer
346 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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1answer
50 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, ...
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14 views

Doubt about the LFW‏ database

I post below a part of the mail I wrote to the creators of the database LFW: i am currently working on a face recognizer which has given me very good results in small tests performed, now i would ...
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1answer
72 views

Image gradient light-to-dark, dark-to-light

From link: Black-to-White transition is taken as Positive slope (it has a positive value) while White-to-Black transition is taken as a Negative slope (It has negative value). So when you ...
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2answers
54 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 ...
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1answer
77 views

Computer vision, Coupon code detection, sugested algorithms

The telecommunication operator in my country has coupons that used to recharge the balance I want to develop an Android application, that with the camera can take the scratched number and recognize ...
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3answers
120 views

HDR Imaging - Exposure Compensation

Tried HDR Algorithms of OpenCV. Since the algorithm takes pretty much time. I tried few alternative steps as follows. Took sample images from: HDR Images 1. Divided the image into four equal regions ...
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1answer
105 views

Finding Distance between Cameras in Stereo Vision

We know how to create disparity map from stereo vision with OpenCV. My question is How can we find/estimate distance between cameras from two image taken from these cameras in OpenCV?
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1answer
34 views

How are the scaling parameters included (extracted from) an essential matrix?

An essential matrix relates corresponding points between two images assuming that a camera satisfies the pinhole camera model, and can be expressed as: $$E=K'^TFK$$ where K is the calibration and F ...
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34 views

Find horizontal and vertical derivatives of image

I need to find the horizontal and vertical derivatives of an image using the kernels [ 1 0 -1] and its transpose respectively, using Python. I am a newbie in Python, and don't seem to find any inbuilt ...
2
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1answer
62 views

Obtain motion between image features by means of the homography matrix

I have been reading several really good answers about how to obtain camera pose (rotation, translation, etc), such as this one and this one, but I am not sure how this applies to my problem. My ...
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2answers
101 views

Understanding this Gabor Filter equation

I am working on a project where I need to implement road edge detection. This research paper suits my requirement in the best way, so I am studying it: ...
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62 views

Live Video processing using hadoop?

How can I process a live video stream using hadoop? Case in point is Opencv, how it processes a live video frame by frame. Can it be done in hadoop? Else, can a mechanism be made in which opencv ...
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26 views

how to compute horizontal angle of a pixel from a computer vision camera

My program needs to compute the angle of a pixel from a computer vision camera that has 120 degrees field of view, and resolution of 640 pixels wide and 480 pixels high. Program receives an X,Y array ...
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2answers
91 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 ...
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1answer
28 views

2D DWT Image Issue

In the literature, I see that a 2D signal can be transformed by first doing a 1D transformation on each row of the matrix followed by the same procedure on each column. It seems that $k^{th}$ level ...
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1answer
90 views

Detecting defects/differences in printed images

I've been experimenting with various methods to detect defects in printed images. Features that are qualified as defects may include scratches, discoloration, etc. I'm not very experienced in image ...
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200 views

Opencv circle detection android

Goodmorning, I have to do a circle detection with android studio using opencv, i follow the example find in internet but it didn't work and i don't understand why, i'm new of android. Can someone help ...
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2answers
147 views

Detecting water level in an image

I have designed a surface with a shape like a rounded rectangle and I want to detect its exact boundaries in a photo I take from it. A sample photo is like this: I have tried thresholding the image ...
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1answer
283 views

Difference between cv::subtract and operator - in cv::Mat OpenCV

What's the difference between cv::subtract and operator - in OpenCV? Mat original = imread...; Mat smoothed, difference, result; smoothed - original image ...
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97 views

2D Log-Gabor implementation in C++?

Is there anywhere out there a 2D log-gabor implemenataion in C++? I have been searching all day and I just couldn't find a normal implementation. I just want to test the filter in my prgoram and I ...
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1answer
43 views

Mat and int are incompatible? [closed]

anybody knows what this is? Mat mat = (Mat_<double>(3, 4) << 0, 0, width, width, 0, height, height, 0, 1, 1, 1, 1); I dont know what mat would be in ...
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2answers
166 views

How to find the actual size of an existing object from the pixels of an image?

I am quite new to vision and OpenCV, so forgive me if this is a stupid question but I have got really confused. My aim is to detect an object in an image and estimate its actual size. Assume for now ...
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3answers
179 views

Segmenting and labeling chessboards through computer vision

With almost no experience/knowledge in computer vision, I am currently trying to segment and label the separate squares on a chessboard (i.e. a1 ... h8). My goal is to use the information to ...
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1answer
631 views

Computing cross-correlation of two images using OpenCV

I have a program that uses OpenCV to compute either the convolution or cross-correlation of an image with a specified kernel. I compute cross-correlation by setting the conjB flag to true when calling ...