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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Help in Retraining a HOG Descriptor using SVMLight

I am currently trying to count cars using OpenCV 2.4.4 with a HOG descriptor. Because a model for car detection is not available in OpenCV, I am creating my own model using SVMLight and a dataset of ...
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1answer
2k 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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OpenCV face recognition: Finding a best match

I am working on OpenCV2.4.2 C++ interface for face recognition functionality. The face recognition feature seems to be working fine on standard databases. (AT&T, Face Recognition Data, University ...
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Correct Fish Eye camera Radial Distortion and blurry effect at the image edges

There are a lot of questions regarding this topic ,but I am trying to get a more clear picture from these questions. I am trying to calibrate a fish eye camera and I am using OpenCV omnidir class ...
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842 views

Optimal measurement model for Kalman in Augmented Reality

I am developing an augmented reality SDK that uses Kalman for tracking a planar marker. My state is composed of 3D position, a quaternion, velocity and angular velocity. \begin{bmatrix}{\vec{p}}\\{\...
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1answer
52 views

What impact have different types of border-handling on high pass or low pass filtering?

When high or low pass filters are being applied to an (grayscale) image, the borders need to be handled separately. They could be filled with 0's or 255's (b/w), repeat the nearest pixel value, or ...
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182 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
2k 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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236 views

stones' detection in jewel image

The project I am doing is to detect stones in an image of a jewel, so as to get the idea of the deduction to be made in the gross weight of the jewel. I have done image-segmentation in the HSV color ...
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435 views

Efficient Hessian-Laplace blob detector implementation

As it is mentioned in a paper for SURF, it is possible to approximate hessian determinant using integral images. If I want to implement Hessian-Laplace detector, is it feasible to also approximate ...
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Why is LBP generaly faster than HAAR?

I am digging into Haar like and LBP features. More precisely its implementation in OpenCV. Every article or forum entry I found states, that LBP is faster than Haar. My local tests also confirm this ...
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MPEG-7 descriptors' implementation in OpenCV

I'm looking for implementation of MPEG-7 descriptors which are compatible with OpenCV's recent versions and containing "region-based shape descriptor ART(Angular Radial Transformation)". I ...
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456 views

Motion and Distortion Estimation using multiple still images?

TL/DR: I'd like to take the median of lots of images to make a single "better" image. The problem is, the camera is slowly moving, and there is significant lens distortion. On the plus side the ...
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752 views

Why do object-boundaries look better on a badly rectified image?(openCV stereo correspondence)

I got 2 pictures which is almost parallel, and not positioned very far from each other. I'm using OpenCV to try to create a disparity map (Stereo correspondence). Because I'm trying to use it in a ...
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206 views

There are other shape properties scale-rotation invariant except HuMoment?

There are other shape properties scale-rotation invariant except HuMoment? There are example that show me how can i implement them? I find this example in c++ https://stackoverflow.com/questions/...
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How to recognize a zebra crossing from top view using OpenCV?

How to recognize a zebra crossing from top view using OpenCV? It is not a straight zebra crossing - it has some twists and turns. I have some ideas: parallel line detection, but the available ...
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445 views

STASM or AAM which is more efficient

I am working in face detection and recognition project. I am using STASM for face detction and locating face landmarks. On googling I found AAM (Active Appearance Model) and found that it is also used ...
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OpenCV detecting elbow

I have to detect my elbow. I'm able to produce an image in which I'm facing the camera, standing before it and my arms are in my body plane(body plane is plane containing my head,chest,and legs)(i.e. ...
2
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1answer
200 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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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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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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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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23 views

Size filtering on binary images

I have noisy images from which I extract the contours using OpencCV's findCountours, which performs binarization internally. This results in innumerable small ...
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KLT tracker, reject tracked occluded points

I want to use KLT tracker for a visual odometry application. Thus, I only want to track object features. Currently I'm using OpenCV's implementation ...
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53 views

Implementing Edge Preserving Diffusion (Anisotropic Diffusion)

I am trying to implement edge preserving diffusion. Recall the general diffusion equation to be: $$\DeclareMathOperator{\Div}{div}\delta_t u = \Div(g \nabla u)$$ Where $g$ is the speed of the ...
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1answer
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How can I detect pipeline cracks using OpenCV and Python?

I have developed a robot that captures images of the pipeline interior as it moves. The requirement was to be able to detect cracks inside. So far i tried several OpenCV codes that find the crack ...
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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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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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Obtaining Subpixel Resolution 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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316 views

OpenCV denoising a 3x3 pixel pattern noise

This picture shows two photos captured by a camera from a black photographic paper. The cross is marked by laser. The left one shows a 9 pixel pattern of noise. This gets in the way of auto-focus ...
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1answer
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Opencv Android Perspective Transformation not working as expected

I'm working with perspective transformation in opencv for android for a personal project. The thing I'd like to do is to acquire a document like CamScanner does. For this I import a picture and let ...
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Line Detection with OpenCV

I'm trying to use the native functions of OpenCV HoughLines and HoughLinesP to detect the lines from an image. The Canny edge output of that image is the folllowing: The problem is that the OpenCV ...
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2answers
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Binarization of image for varying background and foreground colors for OCR

I am trying to develop an automated OCR system for images obtained from the internet. The images mostly consist of computer generated text imposed on a background, so the OCR should produce near ...
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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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53 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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45 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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950 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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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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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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Primitive Feature Detection

I am trying to check whether this black circle is exist or not on my images. My current approach is like that; Hough Circle detection Crop the outer roi Adaptive threshold count zero pixels if ...
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0answers
511 views

Gap Filling Contours / Lines

I have the following image: and I would like to fill in its contours (i.e. I would like to gap fill the lines in this image). I have tried a morphological closing, but using a rectangular kernel of ...
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High triangulation error

I have implemented a 2D->3D point triangulation method, which uses 2 poses P1 and P2 and 2 points back-projected to z=1 point1 and point2 to recover depth: ...
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Visual regression test - Extract elements of GUI-Screenshot - MSER OpenCV

For a visual regression test I need to compare screenshots of webpages (different release-versions). I started with pixel by pixel compare. Actually I split the screenshot in different parts (maybe ...
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Separating similiar object in an image

I have posted a question on Stackoverflow and was suggested to post here. Please refer this question for the images: Similar Question: I have used SURF Keypoints and a FLANN Based matcher and ...
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How to categorize the images based on Illumination / shadow?

Input: Cropped face or Non Cropped face images. Detailed explanation: My project is face authentication. I am using OpenCV face detector to crop face from images. I am using OpenCV implementation of ...
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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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1answer
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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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Do backgroundSubtractor functions in opencv only detect moving objects?

There are some backgroundsubtractor functions in opencv like backgroundsubtractormog2 , backgroundsubtractorGMG and ... . It seems that these functions only detect moving objects in a video and fixed ...
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Tracking of rotating objects using opencv

I need to track cars on the road from top-view video. My application contain two main parts: Detecting cars on the frame (Tensorflow trained network) Tracking detected cars (opencv trackers) I have ...
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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 ...