# 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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### What function to apply a Metamorphopsia (grid warp) translation?

How would I go about finding or creating a function to warp images dependent on grid lines surrounding an origin (I don't wish for a grid on my actual images): It should work in practically the same ...
23 views

### How to know what kind of noise?

Im working with friends on a computer vision project for university. For the preprocessing part we are going to use a Gaussian filter. One of my project partner said I have to justify the use of a ...
42 views

### How to calculate the plane at infinity? either in Matlab or Python

I tried to implement this function to compute the plane at infinity $n_\Pi$ from the equation: where $w^{-1}$ is the image of the absolute conic IAC, $M_j$ is the Projection Matrix of image $j$, but ...
52 views

### Understanding legacy code: Algorithm to remove radial lens distortion

The method below to remove lens distortion from a camera was written more than ten years ago and I am trying to understand how the approximation works. ...
24 views

### How can I infer the cost function from Kruppa's simplified equations

The following equations are Kruppa's simplified equations used in camera autocalibration. My objective here is to infer the cost function(Error Function) from this equations, So I can minimize the ...
9 views

### How to implement a single shot object detector with only “one” anchor box per feature-map cell

I am newbie to SSD model, I have some images of products on a shelf , I trying to detecting that products using SSD with one anchor box per feature map, please help me out, how to prepare the data and ...
6 views

### Learn the relationship between the pixels in a chunk of an image and then search for more chunks like this one

I've just started to learn computer vision and I have a doubt about if I can do the following and how can I do it. If a 4x4 square of the image is like this one: Here I want to detect another chunk ...
50 views

### Gonzales Digital Image Processing and the Laplacian Operator

In Gonzalez' book Digital Image Processing, third edition, he writes on page 182 that It can be shown that the simplest isotropic derivative operator is the laplacian operator where the ...
12 views

### Spectrogram vs MelSpectrogram

I am a university student in computer science and during a project, I run into the Mel Spectrogram. Doing some research, I found that the MelSpectogram is essentially a spectrogram where the distance ...
47 views

### Erosion compotition rule $\left ( f \ominus g \right ) \ominus h = f \ominus \left (g \oplus h \right )$

I want to prove that erosion of a signal by a function $g$ followed by erosion with another function $h$ is equivalent to erosion of the signal by the dilation of the two functions (Erosion property): ...
18 views

### How would one obtain 3D coordinates from 2D coordinates as well as the roll, pitch and yaw values of the observing camera?

I am trying to decipher the ParkNet DNN introduced by Nvidia. With no research paper released, this is proving quite a hassle. Right at the end of the blog post, it is mentioned that, using the roll ...
53 views

### Pixel Binning: Effect on SNR for Hardware vs. Software Binning

Is there a difference in SNR (or any other measure of image quality) between using 2x2 pixel binning in the camera and shrinking the full resolution image in software (cv::INTER_AREA) to the same size ...
34 views

### Low samples numbers machine vision training for object detection

I'm trying to set-up a machine vision application in which I have to detect the position of a printing nozzle (in the red sqaure in the image) in a field of view in order to prcisely position a ganty ...
16 views

### Flat Field Correction - When images are taken at different exposures

The light source I am using is known to have a Gaussian intensity distribution along the height. I took the raw images at "x" seconds of exposure. However, while taking the bright field image, the ...
114 views

### What is the difference between an image plane and a virtual image?

I have the following diagram that describes a camera model (I believe it is the pinhole camera model). Wikipedia has an article about the image plane and virtual image, but these articles do not ...
69 views

### Projecting a vector to another to detect the sparse values of such vector

Assuming we have sparse vector of length $N$ such as $X = [0,1,0,-1,0,1,1,0]$ which has some non-zeros values. The vector $x = iFFT(X)$ is convoluted with another vector $h$ resluting $y = h*x$. ...
30 views

### How the Grayscale images are converted back to RGB?

In case of RGB to grayscale conversion we take the average of R,G,B channels and convert them to Grayscale which has songle channel. How to convert back the Grayscale to RGB ??
177 views

### What is Magnitude and Phase actually represents in Fast Fourier Transform?

When we reconstruct the image from its magnitude only using Inverse Fast Fourier Transform, then why the resulting image looks nothing like but the original image? Can someone please explain me in ...
40 views

### What's the purpose of augmenting an image with a random “gradient”?

I have the following Python code ...
69 views

### Use sparse optical tracking to track a Bounding Box object

I need some help on solving this issue. Any tips are appreciated. The goal of the project is to try to track a Bounding Box object, chosen arbitrarily in an image, throughout many frames of a ...
63 views

### Is HSV Color Space Sufficient for Rudimentary Color ID and Edge Detection

I want to, as part of a C++ school project (no OpenCV), work with an RGB image taken from a camera filming smarties (round colored pellets) from above and extract the number of candies in each color. ...
89 views

### Why are 8 points needed to compute a fundamental matrix?

Homograpies have 8 degrees of freedom. Fundamental matrices have 7. Essential matrices have 5. To the best I could find, all those matrices are obtained by using the 8 point algorithm. I don't see ...
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### Fast Document Enhancement

I followed Dropbox's blog - Fast Document Rectification and Enhancement To enhancement image, I need solve this formula J(x,y) = gain(x,y) * I(x,y) + offset(x,y) Where J is image after ...
53 views

### Harris Corners Detector squared derivatives

I have trouble understanding something (small) regarding the math behind Harris Corners Detector. (for example I looked at this explanation - https://aishack.in/tutorials/harris-corner-detector/) In ...
41 views

### Parameters for inverse image distortion

I'm trying to simulate camera (barrel/radial) distortion, and to reverse it. I.e. a process that would do: Image --> Distorted Image --> ~ Image In ...
86 views

### Computationally Efficient Ways of Determining If Pixels Are Clumped

I'm working on an application where I get a video frame that's already segmented into good and bad pixels (as in -- the hardware either coughs up a pixel value or a flag that says "bad"). I want to ...
57 views

### Understanding outputs of image Fourier Transform in Numpy

I am trying to understand the meaning of FFT outputs with respect to images. Take a look at the following example: ...
11 views

### Image extraction post processing to increase similarity

I’m trying to train an OCR model, but I need to get my extracted images to look more like the training images. However I’m not sure of how to go about it and what techniques I can use. For instance ...
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### 3D model from high speed videos?

Is there a way to convert or somewhat replicate RADAR data from a set of given high speed videos taken from multiple angles. The problem is quite ill defined but the task I have in hand is to ...
81 views

### 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 ...
27 views

### modelling radar system for image generation

I am trying to find or derive some model for radar using python and blender which should hopefully create a simulation of what a radar image of the blender environment would look like. I have been ...
38 views

### Measurement of moving objects using computer vision

I am working on a project to measure lengths of the black objects and distance between them using computer vision (Shown below in the fig.). These objects are moving on a conveyor shown in the blue ...
110 views

### Remove brighter regions in an image on frequency domain

I'm newbie and maybe this is not the right place to ask this question, or this question has no sense. I'm very interested in working on filtering images on frequency domain. I have found a few ...
23 views

### What are the tradeoffs in HSB and HSV versus CIE color models in computer vision?

I coded a computer vision algorithm to detect objects in different lighting conditions using HSV. I recently read a convincing critique of HSV by Charles Poynton: HSB and HLS were developed to ...
281 views

### Effect of Resizing (Up Scaling) an Image on the Ability to Detect / Recognize Objects

I work in a research lab and am currently setting up a system to image objects approximately 30 microns in diameter with a 250x USB microscope, then use image subtraction to isolate the objects as ...
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### Getting the right frequency (using FFT)

I am implementing the method from this paper: https://dspace.mit.edu/bitstream/handle/1721.1/66243/Picard_Noncontact%20Automated.pdf?sequence=1&isAllowed=y The main idea is cardiac pulse ...
25 views

### 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 ...
391 views

### Understanding the Bilateral Filter - Neighbors and Sigma

I have been reading about the Bilateral Filter in - Fast Bilateral Filtering for the Display of High Dynamic- Range Images and have felt crippled and confused while understanding its working and the ...
130 views

### Losslessness of Laplacian Pyramid

I was just reading up on the Gaussian pyramid and the Laplacian pyramid, used in compression applications of image. The source is here - Carnegie Mellon 16-385 Computer Vision - Spring 2019, Lecture 3 ...
26 views

### Combining Multiple Point Clouds

I have a car with 8 lidars, each with a field of view of 60 degrees. My car looks like this How can I merge all the lidar readings into 1 point cloud?
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### 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 ...
230 views

### How are line pairs and pixels related in image resolution?

I hope this is the correct place to ask this. If not, please refer me to a better place, thanks. Now to my question, I am learning about digital image processing, and the book I am reading is ...
56 views

### Camera Pose Estimation from Vanishing Points

I want to estimate the pose of camera (Location and Orientation). Can I use Vanishing Points to get the location and orientation of the camera? There is object in the image which I also know his size,...
155 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(...
179 views

### Understanding 2D alignment using least squares

In Computer Vision Algorithms and Applications book by Richard Szeliski, the author explains 2D alignment using least squares as follows: Given a set of matched feature points ${(x_i, x_i')}$ and a ...
110 views

### Why reprojection error is minimized instead of triangulation error for bundle adjustment?

For bundle adjustment optmization why is reprojection error minimized instead of traingulation error or ray-to-3d point error? Disadvantage with reprojection error is: for perspective camera, its ...
84 views

### Can the colors of an image be interpreted as “virtual” Doppler effect? [closed]

In astronomy, the Doppler effect is used to estimate approximate distances to stars and other celestial bodies. Using the same principle, lets say we divide an image (photograph) in pixels and that ...
165 views

### How would you interpret the pattern in this picture? (generated by re-sorting pixels based on their RGB value)

Was playing with some pictures and ran the ruby code below. The code reads an input image using the ImageMagick library, gets an array of pixels, re-sorts the pixels and then writes out an image with ...
57 views

### Stereo triangulation similar triangle derivation

I understand that the similar triangles are the red and blue triangles. I'm trying to understand where $T + x_r - x_l$ comes from. I understand we are trying to compute the length of the base of the ...
41 views

### Fast and Slow motion video detection using Optical Flow

I'm trying to calculate a "video motion" value in a given video sequence, meaning how fast or slow motion the video is. For instance, if a video is about a car racing, the value is high. Whereas if ...