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Questions tagged [computer-vision]

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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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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29 views

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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37 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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240 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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202 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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130 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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111 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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23 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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677 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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121 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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17 views

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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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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51 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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62 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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46 views

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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55 views

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
369 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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53 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
292 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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111 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

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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44 views

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
33 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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504 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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31 views

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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152 views

Best approach to check the result of color space conversion from RGB to LMS?

I'm currently working on manipulating the order of RGB color from an image into RRB, GGB, etc. Now I need to convert this RGB value into LMS. I take this paper as a reference for the transformation ...
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1answer
49 views

What is difference between along the edge and across the edge

I am trying to implement a paper called structured tensor based image interpolation. In the paper I came across a concept called tangent direction and normal direction. What they mean is tangent ...
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2answers
1k views

Camera calibration and extrinsic parameters for perspective transformation

I'm working in a photogrammetry camera and laser application where I need to measure a displacement in a specific plane, this is a quick diagram of the setup: In order to get proper measurements I'm ...
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1answer
367 views

Block normalization of histogram of oriented gradient

I am a beginner in image processing. I have some questions regarding HOG. https://www.learnopencv.com/histogram-of-oriented-gradients/ From this website, it mentioned that each element inside the ...
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1answer
897 views

MatLab - Can not detect all lines in a “simple” image using houghlines

I try to detect all lines in an image with some common geometric figures. The obvious choice, hough of MATLAB wouldn't print out the desired results. I used the ...
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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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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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Resolution and accuracy of a stereo camera

My question is pertaining to how the parameters of a stereo camera system (focal length, base, height, pixel density) affects the accuracy as well as the resolution of depth measurement. I do not ...
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1answer
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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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65 views

How to overcome effect of intensity variation in image processing?

I want to process an image for which I need the method to be robust to lighting conditions. For that the only thing I can think of is normalising intensity. I did this by dividing the image with ...
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52 views

Best focus image of stack

I am trying to find the image which has the optimum focus of a focus stack (10 images). I am able to find the best two images by using the minimum gray intensity values but now the problematic part ...
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142 views

OpenGL Image warping using lookup table [closed]

I am working on an Android application that slims or fatten faces by detecting face. Currently, I have achieved that by using Thin-plate spline algorithm. http://ipwithopencv.blogspot.com.tr/2010/01/...
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1answer
428 views

How is WSNR (weighted signal to noise ratio) defined?

I'm studying about comparison between images to determine quality. I've learned about MSE, SNR and PSNR, and now I'm trying to understand WSNR, which I assume is similar to SNR but with weights. I ...
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1answer
386 views

Edge detection in low contrast images

I have some images which have some objects of my interest. The objects have very low contrast w.r.t. background and I would like to detect the edges of these objects in these low-contrast images. Any ...
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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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1answer
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Detect circles in image

I have an image that has pixelated circles in it (a cross section of wires). I want to identify the wires, their location and count them. The circles never overlap and the wires are all within a 95% ...
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56 views

How does the bandlimit of an image reduce by an octave in Gaussian Pyramid procedure?

Reference paper 1. For arguments sake, let's say that the maximum and minimum frequency in an image are 256Hz and 1024Hz. When I perform filtering using the gaussian function, the "bandlimit" reduces ...
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139 views

Frame overlapping

I 'm reading the following article from NVIDIA which involves some audio processing a the beginning : link just here (part 3.2) I don't understand the following part : In practice, we use 520ms ...
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1answer
250 views

Pattern matching methods: Based on Area and Based on features

Good morning, I'm new to image processing and I'm currently working on a project for pattern matching and OCR more specifically. In the state of art I've found the matching process can be classified ...
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2answers
749 views

What happens when we reconstruct a signal after its Fourier transform is done and some frequencies are altered? [closed]

Since we loose time information when we take a Fourier transform, what happens if we alter a few frequencies from the transform and then reconstruct the signal, do we get the altered frequency at the ...
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1answer
24 views

Are there paper about black box testing of optic flow algorithms?

Do papers exist about comparisons of the resulting optic flow and its precision compared to the used optic flow method? I would like to find paper that dealt with this topic in some way and had ...
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48 views

Would it be possible to reconstruct 3d trajectory of ball projectile using only monocular video

Assume ball location on the image frame in each timestamp is given. Would it be possible to reconstruct the ball's 3d trajectory in the camera's coordinate frame? The ball should be able to ...
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1answer
218 views

Algo name: detecting elongated shape in 2d image by convolution with directed lines

I am detecting a shape with roughly known orientation (obtained by using Hough line transform) in thresholded binary image by convolving the image with line with that orientation, and counting the ...