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

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Signal in frequency domain with OpenCV dft

I am experimenting with cv::dft: a 1HZ sinus signal is generated, and displayed in the frequency domain. But for some reason it hasn't got the maximum component at ...
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41 views

Weird features mismatch using SURF

I'm trying to use SURF to detect an object (particularly a cur number plate) in another image. After unsuccessfully trying to use OpenCV i have moved to MATLAB. Everything works perfect on MATLAB's ...
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304 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 ...
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11 views

How can I do operations only to the perticuler segment of image(non-rectangular, Ex: Triangular region) in opencv, python

I use opencv with python to implement the segmentation based on delaunay triangulation. So, I used the subdiv2d as for the triangle generation. What I want to do is,...
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25 views

What does opencv `mean` function do when passing a mask of zeros?

INTRO I am looking at this project to implement some changes. The project is written in C++ using openCV library. Its goal is to detect cars in parking area to calculate the number of free spots. It ...
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24 views

Lane marker detection on KITTI dataset

I have just started on image processing and i am looking for ways or ideas to do object detection. My ultimate objective is to segment out the static road objects such as lane markers and arrow signs. ...
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22 views

Scale and Rotation invariant color based feature descriptors

SIFT/SURF/ORB etc are grayscale based, if the two grayscale bitmap is very similar, but the RGB channel is quite different, how to classify them? So, I think there should be some color based feature ...
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40 views

How to find the probability of Kalman filter states? [OpenCV+Python]

I am working on a video object tracking problem. I am using Kalman filter to predict and correct the object position return by an algorithm such as CamShift. I want to adjust the likelihood ...
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16 views

Compare images of road marker

I just want to check my approaches to the problem and see if they are really correct or whether there can be a better way Problem: I have a scene of road marker (they are predominately lane lines, ...
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18 views

What is the size of Kernel I should Keep when using Sobel filters for finding Vertical Gradient of Image?

I've trying to find the vertical gradient of OCT images of retina and extracting top 3% of images to create an image containing my point of interest ...
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214 views

blur detection using opencv

I'm writing a script to detect blur images using OpenCV by applying Laplacian filter and calculate the std but there is a problem the std for images that contain motion blur is very close to those ...
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32 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 ...
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43 views

Automatically detect an image collage

I'm trying to automatically detect if an image is a collage vs a single photograph. I'm not too concerned with difficult cases of artistic collages. What I'm trying to solve is rectangular collages ...
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30 views

Output of a bank of gabor filters, derive ellipses like regions

I'm trying to implement an algorithm that show how to detect wrinkles in clothes, without going to much into details this is the step that is confusing me. Assuming we have an image $I$ and a set of ...
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43 views

API/ Library for re-orienting 360 degree camera frame efficiently

I am trying to correct the orientation of a 360 degree camera frame using roll, pitch and yaw estimates coming from my C++ Extended Kalman Filter (EKF) code. I am interested in using libraries and ...
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1answer
39 views

opencv otsu binarization not working

I tried to apply opencv OTSU binarization on the following image, but it generate a black image. Here is the following python code: ...
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40 views

Object Position and Orientation in World Space using planar marker

I'm new to computer vision and OpenCV stuff. I've to find Object position and orientation in world space. What I'm doing is, Video monitoring of Aruco marker attached on object. Using ...
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29 views

Wiener deconvolution in cpp giving back the same image

I was trying to deblur a noisy image using wiener deconvolution. I found this code which added noise to an image and removed it as well. Modifying this code only i tried to implement the exact formula ...
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61 views

Gaussian Equivalent of Convolving an Image 50 Times with a Box Filter

I have a image that I'm convolving 50 times with a box filter, and I like to replace this with a single gaussian filter. Because both box filter and gaussian filter are separable I can just study the ...
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84 views

How to detach overlapping contours but not to remove small ones. Alternative to erosion-dilation cycle

Background: I'm trying to detect trees on a sequence of aerial images by calculating a stereo disparity for consequent pairs of images. This is how disparity looks like. White spots are trees: Next, ...
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118 views

How to recognize speech bubbles in comic strips (Ideally OpenCV)

I need to recognize speech bubbles to send to OCR and also to know where they are in the strip. How could I do this with OpenCV? I'm using OpenCV 2 and Python 3.6
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26 views

Techniques for recognizing white rectangular labels in these pictures? (Ideally OpenCV)

I need to recognize these two types of labels. zBar does recognize some of the barcodes sometimes, but I'd need to catch the ones that it doesn't and detect the label, so I can try and straighten up ...
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64 views

Skewed rectified aerial images

I have a series of aerial images from which I would like to get disparity maps for every consequent pair. In order to do that I do a stereo rectification. The problem is that sometimes rectified ...
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1answer
58 views

Redistributing Color in a RGB Image According to a Gaussian Distribution

I haven't done this stuff in a while. If I have an image $I$ I can equalize the histogram of the image using some opencv procedure, it's already defined. Equalizing an histogram means essentially to ...
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2answers
253 views

Fitting a gaussian image using opencv

I'm reading through the opencv documentation and some questions in SO but it doesn't seem to provide this information. I've an image $I(x,y)$ and I want to find a gaussian function $f_{\mu,\Sigma}(x,...
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Given a image of white lines forming a grid, how to get masks of the interior shapes using opencv?

I am trying to determine if there are pills in different cells of a pillbox. I have a raspberry pi camera that takes pictures of a pillbox at regular intervals. I would like to use computer vision ...
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Approach for determining which cells of a pill box are empty using opencv+python

I am trying to use opencv and python to determine which cells of a pillbox has pills in it (see picture 1). My original approach was: Detect edges using canny Draw lines using hough transform find ...
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Pattern recognition

I am new to the world of computer vision, so please excuse my basic questions. I have two patterns: one consisting of a single circle of radius $r$, and one made of several circles, still of radius $...
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How to measure relative distance (Y axis) between two physical objects? - AR app

I am currently developing an AR app that reacts to various positions of physical objects (lego-like bricks) that are placed on the desk in a real-time. If I place the first block on the desk and ...
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Object Recognition: building a system with low resources to recognize an object

Im new at the CV topic. Im dealing with building a system with low resources (raspberry pi 3, Mysql-DBs) to recognize objects and declare if it is in the correct place. Let me explain better... ...
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157 views

How can l get dense optical flow on superpixeled consecutive frames

l would like to compute dense optical flow over two consecutive frames frame 1 and frame 2. ...
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1answer
1k views

Line Detection with OpenCV and Python [closed]

Why do we get less amount of lines then desired in line detection using HoughLines tranformation from OpenCV? How could we improve this method and get all the lines appearing in the image? I would ...
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78 views

Manipulating RGB color by copying channel value

I have a picture and trying to swap the RGB channel into RRB, it's like I need to change all G pixels value into R. I did that by copying the R pixel value to G and store it into a new image file (Mat)...
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855 views

Given a set of lines, find only those who are parallel (perspective)

I have an image which includes straight borders which I need to detect: The borders are thick, which causes hough transform to detect multiple lines for each border, as can be seen in the following ...
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image processing : Segregating panel vs house like structure

I am working on a problem that involves segregating solar panel vs house. Both the house as well as panel are of same color. NOTE: There are two houses in the image. I am referring to the one which ...
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Shadow removal opencv python

How do I remove a shadow after MOG2 background subtraction using OpenCV Python? I used all morphological operations, gaussian and median blur, thresholding. it removes noises but deep shadow is ...
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93 views

Any other method similar to template matching?

I am trying to identify the basketball courts in my area, I've tried multiple methods/tutorials from the OpenCV website. E.g. Feature Matching + Homograph, Brute-Force Matching, FLANN Based Matcher, ...
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479 views

How to detect curve in chart grid?

I would like to detect a curve in a grid. Example (hand-drawn): https://imgur.com/a/WsE85 I would like to detect the intersects of the curve with the vertical gridlines marked with the "x" symbols. ...
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people detection

I am doing a project to count the number of passengers using opencv. Does background subtraction give best result? How do I count the number of people based on the number of bounding boxes (detected ...
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335 views

Why entropy is undefined in low contrast image

I am trying to measure contrast of image by entropy of histogram of image. Code for computing entropy ...
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190 views

analysis of two static images in FFT and time domain

Here, i want to analysis frequency domain for two static images. So far i know that in FFT, we can separate high and low-frequency components. In magnitude frequency spectrum, the low-frequency ...
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467 views

How to handle lighting conditions?

I need some image processing techniques in part of an application with a robot. The robot captures an image of objects on a whiteboard. The goal is to detect the contours of these objects and compute ...
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1answer
500 views

Calculating distance between two blobs in a binary image in microns

I have a monochrome CCD camera with resolution 960 X 1280 and can give up-to 15 fps I am working on python opencv. I want to track the distance between two rectangular blobs in binary images in real ...
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Obtaining SubpixelResolution for video processing in python

I am working on a video processing application to calculate distance between two points using opencv Specs : Linear Pixels - 1600. FOV - 100 mm Resolution per pixel using above data : 62 micron ...
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How to choose good features for my machine vision application? [closed]

I am trying to create an application (with OpenCV3) that can distinguish sidewalks from streets by a real-time camera that is embedded in a glass. I have 3 question about this project: Which features ...
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1k views

Does the cv2.waitKey argument determine the frame-rate while capturing a video?

Kinda new to image processing, so pardon me if the question is too stupid. Using the library cv2 in python to capture video from my webcam, which, so far as I can see as a programmer, is basically ...
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804 views

Improving Template Matching Algorithm for OpenCV

Car detection using OpenCV I am working on a small personal project where i have to know wether an image shown is a car or not. I am using the basic OpenCV python based template matching. Positive ...
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915 views

computer vision - How to correctly calibrate my camera with a wide angle lens using openCV?

I am trying to calibrate a camera with a fisheye lens. I therefor used the fisheye lens module, but keep getting strange results no matter what distortion parameters I fix. This is the input image I ...
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51 views

Determining the pattern direction of a bitmap image

How can I obtain average direction of the pattern shown in the figure below. It is the direction of the red arrow relative to the yellow (horizontal) line. Any ideas for an approach? I couldn't figure ...
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Get the correct solution for rvecs and tvecs for camera pose estimation, using SolvePnP in OpenCV C++

I am trying to measure the pose of a camera and I have done the following. Mark world 3-D(Assuming z=0, since it is flat) points on corners of a square on a flat surface and assume a world coordinate ...