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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2answers
95 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 ...
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2answers
4k views

ORB Algorithm: What Is Intensity Centroid?

So, I am reading a paper about ORB: An Efficient Alternative to SIFT or SURF and it happens to calculate the direction of corner from it center . According to Rosin the author of the paper;moments of ...
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1answer
390 views

How to remove striped noise from this image. Which filter or algorithm use better?

I need to process a gray scale image. The task is to remove the stripes, which constitute some noise. I have next origin image: This image received many channels ADC(Y) in moment of time (Xn) from ...
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0answers
25 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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2answers
3k 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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0answers
39 views

Matching Coordinates between two images

I am using images and corresponding lidar values for depth estimation CNN. I have RGB images. Corresponding to each RGB images, there is another image representing a subsets of pixels and distances to ...
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0answers
42 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
185 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 ...
67
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9answers
82k views

Why do we use the HSV colour space so often in vision and image processing?

I see the HSV colour space used all over the place: for tracking, human detection, etc... I'm wondering, why? What is it about this colour space that makes it better than using RGB?
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120 views

What is scale ambiguity in computer vision?

When you compute relative pose between cameras, translation is only accurate upto a scale. Need some help in understanding the scale ambiguity and what exactly does it mean translation is accurate ...
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3answers
19k views

Object detection versus object recognition

I have a slight confusion differentiating between object recognition and object detection. Some people say object detection is a sub-topic of object recognition? Can someone clarify the the difference ...
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1answer
133 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 ...
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0answers
20 views

Measures of edge image continuity and connectivity

Suppose I have a scalar image $I:\mathbb{Z}_{1,m} \times \mathbb{Z}_{1,n}\rightarrow [0,1]\subset \mathbb{R}$, where $\mathbb{Z}_{1,m} = \{1,\ldots, m\}$. (For instance, computed as the (scaled) ...
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2answers
11k views

Understanding SURF Features Calculation Process

So, I was reading the paper on SURF (Bay, Ess, Tuytelaars, Van Gool: Speeded-Up Robust Features (SURF)) and I can not comprehend this paragraph below: Due to the use of box filters and integral ...
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1answer
853 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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1answer
1k views

What's the Difference Between UQI and SSIM Measures for Image Similarity / Quality?

I'm studying image quality assessment (IQA) problem and I'm currently learning about quality measures UQI and SSIM, I know UQI is a predecessor of SSIM, but they look exactly the same for me...
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3answers
80 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 ...
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2answers
157 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 ...
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1answer
919 views

In Plain English, What Are the Within and Between Class Variances in Otsu's Thresholding?

For the past week I've been through numerous research papers and tutorials on Otsu's thresholding. Even wrote to the authors, but every single one of the explanations are in terms of "Class" and "...
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0answers
40 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 ...
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1answer
49 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 ...
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2answers
326 views

Scratch Detection On Noisy Textured Surface

I wish to extract long thin scratches from the noisy background image.I have tried several ways such as stacking smoothed image with input image to remove some of the noisy background patch before ...
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0answers
153 views

The rank of Fundamental Matrix

This question is regarding two view geometry where a point lying in the image plane of the first frame/ position of the camera is mapped onto the image plane of the second frame/ position of the ...
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1answer
25 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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0answers
8 views

BRIEF feature vector random point sampling 3rd method

When using the BRIEF algorithm to generate a feature vector, 5 methods are provided for selecting 2 random points inside a feature point patch. The 3rd method is described as follows: Let consider ...
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5answers
746 views

Auto Detection of Rotation Angle on Arbitrary Image with Orthogonal Features

I have a task at hand where I need to detect angle of an image like the following sample (part of microchip photograph). The image does contain orthogonal features, but they could have different size, ...
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0answers
11 views

What is the name and theory behind a basic motion filter with background update?

I am working on machine vision task. I am using openCV in Python. I need to detect motion. Best would be if I can calculate the difference between the new image and background. However, the ...
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0answers
14 views

Sparse to Dense Flow

I'm trying to upgrade a flow from sparse to dense and have been recommended this for my use-case https://uk.mathworks.com/matlabcentral/fileexchange/25634-smoothn . When I run the interpolation, ...
9
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1answer
855 views

Removing Noise from Dental Radiography

I'm working on a project of applying Active Shape Model to locate tooth in dental radiograph. For those familiar with the technique, I'm currently trying to sample along normal vectors for each ...
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2answers
274 views

Filter for Reducing Background Noise in Image

I have images where there is a lot of "black" background (few shades of black). (In many images at least half the pixels are background). I need to get interest points from the image, but because the ...
4
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1answer
1k views

Implement the 3D Structure Tensor in C/C++?

I am trying to figure out the details on how to implement the 3D structure tensor in C/C++ in an easy but efficient way and need some advice! For a discrete function $ I(x_i,y_j,z_k)$ the 3D ...
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1answer
338 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 ...
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2answers
114 views

Generate 3D image from Multiple 2D Images

If we're to capture an image of a body using four (4) WebCam with a 16 megapixel (1 in the front, 1 in the back and 2 sides(left and right)). Is it possible to make a 3D out of it using image ...
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3answers
8k views

How to Detect Gradients and Edges in Images?

I want to be able to find points in images that are the centre of a radial gradient like the one shown in the left picture below. Any ideas on how I could use a Hough transform or some other computer ...
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0answers
16 views

Optical flow Horn & Schunck smoothness error

I was reading about the Horn & Schunck method and they define the smoothness error as (Robot Control 1988 (SYROCO'88): Selected Papers from the 2nd IFAC Symposium p. 348): $E_{sm} = \iint{\left(...
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2answers
208 views

Definition of difference between compression and filtering

I'd like to explain the motivation. It sounds like a neuroscience topic but I am after the strict Signal Processing POV. (I don't come from a Signal Processing background). Interested to learn ...
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0answers
69 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 ...
4
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2answers
438 views

How can I learn image processing in a practical way?

I am a beginner in image processing and I have to learn to program in MATLAB as soon as possible. I started with Rafael Gonzalez book, but understanding this theoretical knowledge and mathematical ...
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2answers
213 views

What do the 1D filters represent when using imfilter?

I am reading the source code of an algorithm that is used to process an image. While reading this source code (and others), I've found lines of code of the form ...
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1answer
83 views

Can CV or DS be seriously considered DSP roles? [closed]

This is not a technical question but can have a yes/no answer, and a why statement. My understanding about digital signal processing (DSP) is that it allows to take real-world analog signals (1D, 2D, ...
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0answers
44 views

How does the “additive operator splitting” exactly work?

I am reading about the non-linear (or non-homogenous) diffusion method (aka anistropic diffusion method). There are several ways of implementing this method. In all cases, we first need to discretise ...
4
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4answers
182 views

After advice about detecting focus quality of objects in a photo detected using YoloV3

I've spent the last couple of days playing with YoloV3, and have had very good results. My use case is sports photography, and the object detection for people/bikes etc is very very good, I'm very ...
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2answers
138 views

What Is the Relation Between Deblurring and Deconvolution in Computer Vision and Image Processing?

The deblurring problem can be modelled as follows $$ f = \phi u + \epsilon, \; \epsilon \sim N(0, \sigma) $$ where $\phi$ is a filter (e.g. a low-pass filter) and $\epsilon$ is a Gaussian noise. In ...
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1answer
727 views

What Are the Differences between Super Resolution, Denoising and Deblurring?

In the fields of computer vision and image processing, what are the differences between Super Resolution, Denoising and Deblurring?
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1answer
2k views

How to remove reflections from images?

I've been playing around with making images better and removing all the unwanted disturbances from it. I found out a major concern would be removing the unwanted reflections that might come. I've ...
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0answers
25 views

Understanding SURF point-of-interest localization

I've recently read Herbert Bay's paper of SURF. From which I understand: SURF calculates a table from each image pixel's Hessian matrix's determinant, instead of SIFT's Difference-of-Gaussian table. ...
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0answers
24 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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1answer
252 views

How to Combine / Cascade two `3 x 3` Filters into One `5 x 5` Filter

If you have a uniform 3x3 box filter T which is: 1 1 1 1 1 1 1 1 1 And an 3x3 laplacian filter W which is: 1 -2 1 -2 4 -2 1 -2 1 Can these 2 filters be combined into one 5x5 filter, the ...
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0answers
56 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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3answers
563 views

Backgammon checkers and dice detection

first of all thanks for reading, and sorry for such a generic question. If it is off topic for your forum i would be thankful if someone could point me to a place where i can find an answer. I am ...

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