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Computer vision includes methods of processing, analyzing, images and high-dimensional data to form high level understanding and recognition of the scene or images.

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estimation of the ground plane with pinhole camera model

I am trying to understand the pinhole camera model and the geometry behind some computer vision and camera calibration stuff that I am looking at. So, if I understand correctly, the pinhole camera ...
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Getting a 3D point from multiple 2D points in multiple cameras

I have set of $n$ projective cameras $P_i$ and a single 3D point $X \in \mathbb{R}^3$ that projects as $x_i \in \mathbb{R}^2$ into all cameras $i$. How can I recover $X$ only from only the image ...
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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
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Removing lines of certain length from an image in MATLAB

I want to remove the portion of the line (highlighted by the yellow circles) where pixels form a straight vertical line segment. If I use the strel ...
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what's gray level features and how to compute it with python

Hi I am a new one to computer vision. now I am trying to classify the image into good or bad based on image features. Now I want to use the features in the following paper: https://arxiv.org/pdf/1202....
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Image processing - Why is sum of values of a blurring filter = 1?

Usually, blurring filters have the sum of all the values in the filter matrix equal to $1$. Why is it so?
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converting digital length to physical length using reference object

I am trying to find actual length of an object, say X, from an image. For that I'm using a reference object , say Y, ( object of known dimensions ). From image while converting pixel length of X to ...
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40 views

apply 2x Gaussian filter and then down sample by 2 an one dimensional input, choose parametric sigma to not miss so much information

Please consider a 1-dimensional signal as an input. What are the considerations in choosing $\alpha$ if two Gaussian filters each with parameter $\sigma = \sqrt{\alpha}$ are applied in cascade and ...
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43 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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1answer
20 views

Computer Vision - Does implementation of Hough Transform for lines require a loop for angle parameter?

I am trying to understand how Hough Transform is implemented in real world applications. Consider a line with equation: $y = mx + b$ In parametric form, this line can be represented using (d, $\...
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1answer
47 views

given an image and its fourier transform, find another image fft using fourier properties

I managed to solve few of those questions , but I'm not manage to answer 3 of them correctly, the question is: given an image and its fourier transform, find another image fourier transform ,using ...
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5answers
219 views

Determine when a constant signal changes to another constant value

As a novice to digital signal processing I have a scenario that probably seems trivial but I dont know the answer to. I want to detect when a signal changes but ignore noise. 255 255 255 255 255 ...
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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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64 views

Perspective Transform using depth and scale information

I want to transform perspective on an input image and output image from the new perspective. I have depth map and scale information. The picture roughly demonstrates what I want to do. I have a single ...
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106 views

How to apply a homography matrix after finding it via a common camera calibration technique

I am trying to find a matrix that maps four specific 2D-points to another set of specific 2D-points. Specifically, I'm trying to find the matrix $H$, such that $x_i=HX_i$ achieves the following ...
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1answer
33 views

Selecting gradient orientation for Generalized Hough Transform while scaling and rotation is present

I am using this link to study Generalized Hough Transform. I will explain it briefly. In order to detect a shape, an R-table is created for the shape with $\phi$ indicating gradient orientation for ...
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1answer
53 views

Morphology - Why does the concept of opening and closing images exist when we already have erosion and dilation?

If we consider the closing operation of an image, we first dilate the image and then erode it. So, first we expand the foreground (white pixels) and and then we take away some part of the foreground. ...
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1answer
295 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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Anisotropic filter implementation wrong?

I've this implementation of the anisotropic filter: ...
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Chapter 4, section 4.2.1. in Szelisky computer vision, is there a mistake?

I've already asked a similar question in mathematics exchange without getting an answer, I read a bit more and I think the question might be more suitable for the signal processing exchange. ...
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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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1answer
93 views

Laplacian of Gaussian Approximation and Gaussian Blur as the Solution of Heat Equation

While I was reading SIFT paper(Lowe, 2004), I came across the method that he apply "heat diffusion equation" to Gaussian function to derive that $$ \frac{∂G}{∂σ} = σ∇^2G $$ I searched Wikipedia and ...
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1answer
67 views

The Differences between Super Resolution and Denoising and Deblurring

In the field of computer vision/image processing, what are the differences between super-resolution and de-noising/de-blurring? Thanks.
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46 views

Correlation peformed by convolution

Background: The question here is related to images in particular and not signal/waveforms. I have been reading a lot of answers about the difference between convolution and correlation but I am stuck ...
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1answer
91 views

Automatic Image Enhancement of Images of Scanned Documents (Auto Whitening)

Dropbox have make a blog post about there automatic enhancement method for scanned document image - Fast Document Rectification and Enhancement. I followed the post and they mention a formula to make ...
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1answer
20 views

Lighting for computer vision automisation

Currently I am working on a computer vision project where we want to gather data from a composite material production environment. I have an example picture here: What I learned so far that my ...
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1answer
216 views

Scale invariant template matching

For my application I am looking for a free, fast and scale-invariant template matching algorithm. The templates can only be scaled within the scene (no skew or rotation) and the scale is unknown. ...
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How to extract text from scene images?

I tried many methods for segmenting images like the example below ; but i obtained no efficient result can someone suggest me a good method for extracting text from complicated images like this ...
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43 views

A question about visualizing “Lucas-Kanade(optical flow)” algorithm

I am reading O'Reilly's OpenCV 3 book. In keypoints section(for tracking objects), there is an algorithm named "Lucas-Kanade". in the below image it tries to give a visualization of it but I can not ...
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Detection of calibration (dummy) stickers

I was looking for some commonly used approaches in computer vision to find the following calibration stickers and I was pretty surprised that I have not found any. I am not sure if I am just googling ...
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1answer
167 views

Is there a penis detection demo similar to face detection?

Tutorial for face detection: Is there a script / tutorial / demo for penis detection? These guys ran into some issues: Fairly serious question, future of internet memes is at stake. Breast / ...
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1answer
36 views

How Can PCA Be Used in Image Analysis [closed]

I am still a not how PCA can be used in image analysis and where is it is mostly used. For example how can PCA be used in order to differentiate between different faces? Can you please mention other ...
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2answers
58 views

What are some current algorithm(s) for finding if two images are copies of each other?

Could anyone enlighten me on what are the current best ways to detect if two images are the same (i.e. a copy or edited copy of each other)? What feature detection method do they use (SIFT, DWT, pixel ...
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1answer
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Best way to fill an image placed into a larger box without creating artificial edges?

If you are training a neural net for a bunch of images of different size, and you have to put them all in a same-size enclosing box for input to the neural net, what's the best way to fill the ...
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Estimating the deformation of a printed label in an image

For a university honours project, I am developing an algorithm to read the text on nutrition labels. One difficulty I have encountered is how to 'flatten' the text in images of labels that are very ...
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1answer
94 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
42 views

Good Metric for Spatial Resolution

I am trying to filter crawled images with their image quality. By 'high quality' I mean high resolution, not aesthetic score or perceptual score. However I found that some images have very high pixel ...
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1answer
101 views

How do steerable pyramids work?

I'm reading a paper about texture synthesis using pyramids, and the very first section mention two methods for constructing pyramids, one is the Laplacian Pyramid (which I'm quite familiar with), the ...
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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
52 views

Suggest an image segmentation technique to find the paste radii?

I am new to MATLAB/Digital Image Processing. So pardon me for any typing errors or wrong use of jargon. 1) I am trying to find the paste diameters for a total of 100 images in sequence. I am posting ...
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Signal processing methods for identification of multimedia descriptors for feature extraction (semantics)

It is said in https://www.amazon.co.uk/Multimedia-Semantics-Metadata-Analysis-Interaction-ebook/dp/B005E8AG66 that While there has been a lot of work in the signal processing research community ...
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Scan an Auditorium, Count People, and Display Open Seats

I'm looking for any recommended approaches to be able to digitally process a room full people, like an auditorium or a movie theater and output the following information: Goals: How many people are ...
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1answer
32 views

Is there a closed form solution for a temporal calibration of two different signals?

Given two signals $f_1(t),f_2(t+dt)$ where $t$ is time and $dt$ is the time delay between the two signals, is there any closed-form solution with respect to $dt$? what are the efficient global ...
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2answers
247 views

Camera measurement of heart rate - frequency bias towards 50 bpm (0.83 Hz)?

I am trying to develop a RGB camera-based non-contact measurement of heart rate using principles of remote photoplethysmography. I want to be able to measure a range of heart rates I have been looking ...
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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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How to produce pencil-like images by pure image processing methods?

Is it possible to reproduce the following pencil-like image by pure image processing? Notes: The original image: Fig 10 in paper http://www.cs.columbia.edu/cg/aircode/aircode-uist-2017-li-et-al.pdf ...
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What is the most reliable shape representation for the purpose of detecting humans shapes?

The requirement of the algorithm is to detect human shapes. While the standard HoG or Harr cascade can be used, I am exploring whether the human shape - which primarily includes face+neck+upper-torso ...
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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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185 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. ...