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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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13 views

Trying to make magic color filter for scanned document, but not getting perfect output

I am trying to make a magic color filter for the scanned document but not getting the desired output. In some documents text is distorted in some document, images colors get lost. In some document, ...
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1answer
29 views

How to produce color image using edge detected images?

Hi I am trying to produce an image which is a combination of multiple images such as in focus stacking. Now I have 6 photos and I want to produce a final image such that the final image uses blocks of ...
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1answer
71 views

Detect valve position without colors

I can't find a solution for my problem and I need your help. I have to create an application to detect if a valve is open or close like this : https://www.youtube.com/watch?v=VY92fqmSdfA Some ...
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14 views

Face image quality assessment

I'm trying to filter out bad face images (with artifacts) generated by StyleGAN. Is there a good image quality measurement mechanism in python for doing this? I've tried using BRISQUE but it is not ...
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1answer
19 views

How do I filter out this horizon from my contour?

I am trying to identify the T-rex and obstacles (cactus and bird) from Google's no-internet game. What I have done is: Apply GaussianBlur filter Apply Canny Apply Dilate Apply erode findContours ...
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12 views

Efficient image matching technique for small match library set

Background A scene captured from video frames from an Android mobile device camera are to be analyzed in real-time. The scene will contain up to 12 distinct photos. The library images to be matched ...
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2answers
16 views

Recommended Order of Performing Denoising, Deblurring and Super Resolution on an Image

In the normal workflow of image processing, there are multiple operations, increase image contrast, image denoising, image deblur and image super-resolution. What are the sequence/order of performing ...
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1answer
42 views

Finding Homography Matrix Using Lines

I have some Points and Lines from original image and the corresponding points and lines from top view image. -> I tried to find homography using points Used OpenCV function findHomography(...
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15 views

center of oblique viewed disk with known radius

I also posted this on the math stackExchange, but it also fits to this forum, so I hope it's fine to post it here as well. I'm working on an issue related to image processing that I simply cannot ...
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1answer
19 views

Gender classification using Periocular Region [closed]

I have a dataset of the periocular region, I have images of the male and female periocular region but they are only labeled as left and right periocular region, Folder is a mixture of male and female ...
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20 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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27 views

Detect Colors in an image using opencv python

How to find different colors present in an image? Is K means clustering enough or any other simple way of doing it using opencv exist?
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2answers
32 views

Camera image pixel structure origin

I am using machine vision for industry task with opencv. I have images from a camera monitoring the process. The detailed look at the small part of the image follows: Enlarged: In the detail, it ...
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1answer
49 views

How do I detect the sharp edges in the following image?

I am looking to count the sharp pointy triangular things in the image. However I was unable to do so. One approach I did try was take a convex hull of the contour and then find convex defects but it ...
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1answer
176 views

Outlined text extraction from image using OpenCV

I have some video frames I'd like to extract some text from (for making softsubs from hardsubbed video for learning). The text in question is mostly in Chinese script (some numbers and Latin letters) ...
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1answer
38 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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58 views

How can I calculate homography from the room height and camera calibration matrix?

EDIT2: I've added an assumption that the camera calibration matrix is given. Other factors (rotation, camera pose) are still not given. I want to measure actual lengths of floor edges (blue lines in ...
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1answer
211 views

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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17 views

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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85 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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41 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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47 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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10 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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18 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
133 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
32 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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217 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
229 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
556 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
924 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
49 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
187 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
167 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
4k 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
189 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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2answers
12k 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
946 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
451 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
220 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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2answers
2k 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
201 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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126 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
74 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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1answer
171 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
164 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
1k 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
437 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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90 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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159 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 ...