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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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OpenCV warpPerspective implementation

I've implemented the least squares method to find the homomorphic image to fix the rotation and projection in an image. Now I'm trying to implement the OpenCV warpPerspective method in order to "fix" ...
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How to implement Just Noticeable Difference(JND) of an Image [on hold]

I want to implement the algorithm of 'Just Noticeable Difference'(JND) of an Image with python-opencv or c++.
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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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19 views

What are the meanings of Fx, Fy, Sx and Sy in Image Processing?

I am currently reading a book titled "Learning OpenCV 3 Computer Vision in C++ with the OpenCV Library", and I come across these two equations: ...
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17 views

Once spines recognized, how do I find each individual book?

I want to make a system like the Book Spine Recognition on Youtube. So I read research paper and I built this system. According this paper, I use Hough transform, then I recognize book boundary ...
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39 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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7 views

Adjustments to get better result appyling hough circles

I have the aboveimage and wanted to detect circles spread around the image. I can detect the circles in the middle through hough circles but it does not work out for the left-most circles which exists ...
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16 views

How to separate spliced(photoshopped) part from the rest of the spliced image?

I'm working on a project to detect spliced images and want 128x128 patches at the boundaries of the forged regions. I have the authentic background image and the spliced(photoshopped) one. If I ...
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1answer
42 views

Sum of Squared Intensity Difference for block matching with ORB features, c++

I am trying to implement feature matching algorithm between image reference and image current. The pipeline is as follows: ...
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1answer
25 views

What principles to use, in order to create field that will be read by OCR?

I currently have an invoice, where some numbers are written by hand, and I would need to read them automatically. My past experience is that people who write numbers will them write in so many ...
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63 views

python: how to compute the color distribution of image in the paper with python and openCV

I am computing the color distribution of image as mentioned in the paper: https://arxiv.org/pdf/1202.2158.pdf. ...
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1answer
93 views

python: how to compute the sharpness features of image

I am extracting the sharpness features of image as shown in the following image mentioned in a paper. I have done with the following code. Firstly, use the open cv convert the RGB to HSL (luminance ...
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1answer
210 views

python: how to compute the gray level histogram features as mentioned in the paper, and

Hi I am extracting the grey level features of image mentioned in this paper (part 4.5 low level features). "We describe two low level features that are particu- larly important for photo quality ...
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1answer
563 views

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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2answers
28 views

Segmenting an image into columns

I want to segment the image below (click for bigger image) into columns based on the natural gaps that exist in the columns. The columns should be perfectly vertical and need not be the same size, but ...
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1answer
92 views

How to segment multiple overlapping coins (ellipses)

I am doing a program that counts coins (and tells their value by their size) with OpenCV (C++). Let's say we have an image of some coins. If there is an overlap of two coins at the same time, it is ...
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1answer
119 views

Is it possible to generate depth map from graycode sequence without using printed calibration patterns?

In a camera-projector system, if only the camera's intrinsics are known, is it possible to generate the depthmap fully automatically through a graycode sequence without any manual calibration process (...
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1answer
2k views

Image processing based on wavelet transform in python [closed]

I take the dwt2 for an image and saved it's coefficients (LL,Lh, hl,hh) using pywt.dwt2 (image,'haar'),in my project I have to change them to uint8 but when I change their types and reconstruct the ...
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1answer
118 views

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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1answer
6k 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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1answer
567 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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1answer
238 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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1answer
157 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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1answer
1k 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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33 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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1answer
139 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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40 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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93 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
54 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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0answers
110 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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1answer
107 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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1answer
116 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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1answer
469 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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1answer
270 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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67 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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121 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
107 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
499 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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133 views

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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1answer
2k 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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1answer
189 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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1answer
2k 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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2answers
6k views

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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1answer
716 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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1answer
538 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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1answer
1k 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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0answers
43 views

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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1answer
38 views

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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2answers
3k 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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1answer
1k 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 ...