Questions tagged [computer-vision]

Questions about algorithms for processing and analyzing images and videos.

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16 views

Disparity calculations and camera centers

I'm learning about the disparity calculations and want to calculate the distance for a known pixel. I have calibrated and rectified images already. Now I just want to calculate Z for some pixel x,y. ...
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15 views

How to calculate image gradient with respect to homogeneous coordinate vector?

I want to use the direct method of computing the homography between two images to estimate the plane parameters (normal and depth [= distance from camera]) of a 3D plane. If we have two images of the ...
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14 views

Different types of interpolation used in computer vision

Known codition: four pixels shown in the image $(i,j),(i+1,j),(i,j+1)$ and $(i+1,j+1)$ $a=0.9$ and $b=0.4$ I was able to calculate the bilinear interpolation using the algorithm provided by https://...
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1answer
38 views

Is the Jacobian matrix calculation process correctly on this energy function?

When I implemented the paper Dynamic Fusion published in 2015 CVPR, I came into the trouble with how to solve the energy function: $$E(W_t, V, D_t, \mathcal{E}) = \text{Data}(W_t, V, D_t) + λ\text{Reg}...
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28 views

Will we be able to « see » COVID (or any other viruses) in our environment in the future?

Given that cameras, computer vision and AI are constantly evolving with greater zoom, macro, processing power... is it possible that some day cameras would be able to « scan » a room and detect COVID (...
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29 views

What is the best way to compare two images for similarity if the brightness of the second image was changed?

I calculate similarity percent between two images. Another image is the same with changed brightness. I've already tried comparing by pixel (euclidean distance for grayscale and 0/1 values), comparing ...
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15 views

How to correct distortion from stitching dual camera to estimate homography

I am trying to distort the image obtained from two cameras that generate a stitching image. Unfortunately, I do not have access to the cameras and I would like to know what could be the best way to ...
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12 views

point of view of each pixel with regard to the whole image

I am looking for a technique or an algorithm that outputs a unique number/vector for each pixel of the image. I want to give the pixel a perspective so the neighboring pixels have more visibility and ...
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1answer
20 views

Distance transform with variable “impedance”

The distance transform gives the distance of each pixel in a mask to the nearest zero. E.g. lets take the Taxicab distance transform: ...
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13 views

Drawing a planar intersection from stereo camera

I wanted to recreate the results of this paper, where the authors draw the boundary between two parts of a building from stereo images. The authors mention that the epipole and the intersection of the ...
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29 views

Would a five color display have higher image quality than an RGB display?

We have five types of photo receptors in the eyes but computer color systems just use the three red, green and blue. Three could be motivated if rod and melanopsin sensations are just linear ...
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14 views

How do I choose the right model for production?

I am trying to build a classification algorithm having 28 classes. These classes consists of Logo of companies like adidas , Nike etc. I have very low dataset below than 100 images and greater than 70 ...
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1answer
32 views

Which pretrained model will be best for my dataset?

I am trying to build a classification algorithm having 28 classes. These classes consists of Logo of companies like adidas , Nike etc. I have very low dataset below than 100 images and greater than 70 ...
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21 views

A few questions regarding simCLR

I read this paper obout simCLR and I didn't understand a few things: What is the goal of the temperature parameter τ? How does it affect the loss? What will be the value of the loss for a batch with ...
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13 views

Inverse VR-Vision, theoretical possibilities and the additional requirements

When using VR-Vision for looking around and the vision is from some point of interest, the look-around is a rotation from inside that point and it reqires a record of a 360° photo or a 360° camera ...
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29 views

Stuck on Ejaz and Islam's paper about Masked Face Recognition

I'm relatively new in machine learning and I am trying to put together my undergraduate thesis on masked face recognition. I've read Ejaz and Islam's paper (available at https://www.researchgate.net/...
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1answer
28 views

Trying to figure out the best way to approach this problem with Computer Vision

Newbie to CV here so sorry of this is basic. Here's the deal, I have a program that I run many times. and each run I produce a screenshot. I need to compare screenshots from N-1 and N runs and make ...
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81 views

I think I've found a flaw in this paper: On finding a minimal enclosing parallelogram. Can someone verify it for me?

On finding a minimal enclosing parallelogram I think the problem will occur when we only consider the first clockwise antipodal vertex. I think instead we should consider an edge when there are two ...
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1answer
24 views

How to get a heatmap of pixel influences from a Convolutional Neural Network

If I have a CNN model (let's say I'm using Tensorflow and Keras) that I've trained for a particular task. For example, let's say I've trained it to detect the difference between an apple and banana. ...
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32 views

Is deepfake detection viable?

I'm thinking of doing a project on deepfake detection, but I'm not entirely sure if it is viable. Based on my understanding, how it works is that deepfake generation programs have a generative and ...
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38 views

Interpreting the accuracy of solutions to the correspondence problem

I have two pictures of the same object, taken by a car travelling down the road like shown on the right side of the image below. I want to find pixels of the object in each frame that correspond to ...
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86 views

trouble recovering rotation and translation from essential matrix

I am having trouble recovering rotation and translation from an essential matrix. I am constructing this matrix using the following equation: \begin{equation} E = R \left[t\right]_x \end{equation} ...
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15 views

Why can we not obtain a unique solution for orientation from Essential Matrix?

In computer vision, why cannot we obtain a unique solution for the projection matrix given an Essential Matrix. Why is it said that it can only be obtained upto 'scale' and what does this mean?
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1answer
31 views

Matching superimposed image

We are given two grayscale images, one of which contains a large, mostly contiguous patch from the other one. The patch can be altered with noise, its levels may be stretched, etc. Here's an example ...
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13 views

Are there some papers or books that compactly elaborate the essential part of the multiple view geometry?

I am a novice to visual SLAM and computer vision. Recently I've read a paper "A micro Lie theory for state estimation in robotics" dedicated to introducing the essential part that necessary to ...
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42 views

Computing structure tensors

As far as I understand, the structure tensor is: $$ M = \sum_{(x,y) \in W} \begin{bmatrix} I_x^2 & I_xI_y \\ I_xI_y & I_y^2 \end{bmatrix} = \begin{bmatrix} \sum_{(x,y) \in W} I_x^2 & \...
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18 views

How are epipolar lines useful in computer vision?

Why do use epipolar lines and what are it's benefits in computer vision ?I am unable to find the uses of epiploar lines and how they are helpful although i am aware of epiploar geometry concepts. I ...
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17 views

3D reconstruction from multiple images

Sorry if it's a trivial question but I'am a beginner. I am working on 3D reconstruction from multi-images project. I am working with these datasets. There is a par.txt file including the camera ...
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33 views

3D Reconstruction from multiview calibrated camera

I have a calibrated camera whose intrinsics were calculated prior. Suppose I have multi images with the same camera. Using the first two views.I have the 1) initial reconstruction using 8 point ...
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1answer
38 views

Face recognition system with a sparse dataset

I have a dataset of 100 ID's, each ID with only a single unique face image. How can I develop an effective face recognition system to recognise only these faces? I was thinking Deep Learning but the ...
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1answer
49 views

Performing semantic segmentation on images on word documents

At the moment, I'm making a comparative analysis between two different neural networks for a class. The problem they are both trying to solve is detecting tables on documents. Below is an example of ...
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22 views

How can I compare two faces using facial landmarks?

I'm using first_order_model for an expression transfer between an video and a static image. Part of the algorithm makes a facial comparison to get the frame in the video where the face is best ...
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14 views

Pattern detection by stacking convolutions

CNN use convolutions to perform many tasks. In some architecture, the first layer(s) are basic filters such as Gabor's. Many CNN work by stacking a number of convolution layers to build detectors ...
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31 views

I don't understand formula meaning of computer vision Paper

I am master degree student at Computer Science Department. I started master degree at this year. Now I'm reading two papers about computer vision. Actually before time I didn't have experience about ...
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21 views

What is the best algorithm for detecting the texture of a person's clothes in real-time for a mobile robot?

I am working on the human following robot. the robot extracts a feature of clothes's texture and distinguishes between the people that they stand up in front of the robot. So, the robot needs that it ...
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2answers
68 views

Using a rotation matrix to transform/shift a pinhole camera

I have a pinhole camera model with the following extrinsic (in Earth Centered, Earth Fixed Coordinate, (ECEF) system) and intrinsic parameters. focal length (x,y) = 55000 px, optical center = (2400,...
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15 views

Contrast detection implementation for blur detection in microscopic image

I am currently doing a project where I have to detect if the the microscopic images given are blurry. I tried canny edge detection but they seem to perform not so good in detecting blur. I realised ...
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18 views

Laser Plane Estimation for Laser-Camera system?

I have to set up a system of a laser line/ plane projector and a web camera to localize the 3D position of the laser in the camera image. I've read / come across several resources but the idea is ...
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38 views

Image/Video deblurring

I am currently working on an algorithm that will help to improve shaken blurry images. I know there are plenty of them, such as deconvolution, that is pretty useful though I don't really know how to "...
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55 views

Why HOG angular bins have values between 0 and 180 degrees?

I have learned that HOG angular bins have values from 0 to 180 since the algorithm uses unsigned gradients. I am failing to understand why. As far as I know gradient orientation is calculated as <...
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1answer
41 views

Text detection in computer vision

I'm curious about the way text recognition works in machine learning(or more generally, the question of object vs not object) in computer vision. How are systems trained when the not-object data set ...
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1answer
13 views

“higher intensity” and “high signal intensity” in images

I'm newbie in Computer Vision and image processing. I'm reading the article "Automated White Matter Hyperintensity Detection in Multiple Sclerosis Using 3D T2 FLAIR" and it said: 2.2.4. WMH ...
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18 views

Measuring distance in arbitrary scale point cloud

I have one point cloud(point cloud of human feet) of arbitrary scale. If I have another point cloud(of human feet) with dimensions known, can I get the dimensions of a first point cloud? How will ...
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0answers
34 views

Partial derivatives of bilinear Sampling

I'm going over the paper Spatial Transformer Networks (link). On section 3.3 they introduce bilinear sampling kernel (Eq. 5) $$ V_{i}^{c}=\sum_{n}^{H} \sum_{m}^{W} U_{n m}^{c} \max \left(0,1-\left|x_{...
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2answers
309 views

How to detect number of specific object in an image and it's diameter(size)?

I have two images of IRON RODS (i.e only two images) and I want to detect how many rods are there in each image and get the diameter of each rod in a image? I don'...
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65 views

RGBD alignment without explicit transformation between RGB and depth

I have a set of RGB-D scans of the same scene, corresponding camera poses, intrinsics and extrinsics for both color and depth cameras. RGB's resolution is 1290x960, depth's is 640x480. Depth is ...
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1answer
891 views

Difference between Image Analysis and Computer Vision

I have searched the web and I have only found the differences between Image Processing and Computer Vison (also in this website too). In addition, sometimes Image Analysis is confused with Image ...
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24 views

Using colors in feature detection

Is there any feature detector or extractor that uses color information? Detectors like SURF and SIFT and many others work with grayscale. How do you think, may be transform can be sued to generate a ...
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0answers
47 views

Do image artefacts reveal the original image orientation?

An image is taken and then rotated by an arbitrary angle and cropped. Let us assume that the original image is rather meaningless and is not aligned in any way. Given the rotated image, is it ...
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1answer
138 views

Computer Vision Techniques to find Slope of beach in the 2D Images?

What I am planning to do is to calculate the height and estimate the slope of the segmented Object. The camera will be static and the Object of Interest is the slope of the beach. I am finding harder ...

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