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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How to prove $\int_{\Omega} \sum_{i=1}^{N} f_i(x)dx$ is equivilant with $\sum_{i=1}^{N} \int_{\Omega} f_i(x)u_i(x)dx$

I have a 2D image in $\Omega$ space. Assume that the space can be separated into $N$ sub-regions $\Omega_i$ such that $\Omega_i \cap\Omega_j=\emptyset$; $\Omega_i \cup \Omega_j=\Omega, \forall ...
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16 views

Understanding Eigenface Face Recognition Algorithm Notations

I have been reading the paper from Matthew A. Tusk and Alex Pentland https://www.cs.ucsb.edu/~mturk/Papers/mturk-CVPR91.pdf I got stuck in this part. I have a couple of questions. Assume my ...
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14 views

How to calculate binocular overlap

I have two cameras of which I know focal length, principal point, rotation and position. The cameras are in an ideal parallel stereo system. I want to know with as few calculations as possible how ...
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39 views

How to extract text from a scanned document?

The task I am facing is extraction of rotated text (any angle) from a scanned image(attached Image). The image contains a blue sticker on it and need means in extracting the text (printed text) from ...
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1answer
22 views

How to calculate performance of your object recognition algorithm and compare results with others?

I am working on a novel object recognition algorithm with BoF implementation for my MSc project and it performs fairly well. I am using it on Caltech101 dataset. I want to compare the results with ...
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1answer
24 views

How to gather similar objects in an image?

I am working in a traffic tracking app, I am using a background subtraction approach to obtain information about the moving vehicles. After some morphological operations I obtain blobs of the moving ...
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8 views

Compute the Gibbs energy for second-order neighborhood

I have a question about Gibbs distribution in Stochastic theory. In which, it defined a clique as a a subset $C$ in the whole image $\Omega$ if two different element of $C$ are neighbors. Figure 2 ...
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1answer
17 views

Image processing usign conv-neural net

Okay I am starting to understand the idea of neural networks but I still haven't been able to understand the use/benefits/implementation of convolutional neural networks especially for image ...
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1answer
28 views

How to use ImageNet Database in Matlab [closed]

How to use ImageNet Database in Matlab for object classification or recognition? I didn't find any tutorial which could practically tell me how to train images on ImageNet database and classify the ...
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9 views

What is the state of the art in recovering homography without using point correspondence?

I am interested in the ones that don't make any assumptions about known points, and just uses the shapes to estimate the homography. I found this one, which seems to be done in 2009, ...
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2answers
36 views

why the sum of masks should be one?

I am studying pyramids (expanding and reducing) and I am a newbie. Why sum of the convolution mask should be one when we are using Gaussian distribution? According to When should the sum of all ...
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1answer
29 views

neural network for 3D pictures

I'm wondering if they are some state-of-art algorithms to apply the convolutional neural network approach to 3D pictures, eg. input is no longer a grid of pixels, but voxels. My objective is to ...
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15 views

Difference between cv::subtract and operator - in cv::Mat OpenCV

What's the difference between cv::subtract and operator - in OpenCV? Mat original = imread...; Mat smoothed, difference, result; smoothed - original image ...
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1answer
25 views

Which anatomical model to use as “ground truth” for validating an MRI segmentation method?

I am research in brain segmentation task that classify a brain in to 3 classes : White Matter, Gray Matter and CSF. To validate my method, I used Dice Coefficient that compare my result and ground ...
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1answer
32 views

Invariances in Neural Networks

I have a question about invariances in neural networks. In general, neural nets with enough layers can learn arbitrarily complicated nonlinear functions. Therefore, it's not hard to understand how ...
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10 views

Template matching for object recognition and pose estimation

I am currently reading a series of articles from Hinterstoisser about template-based real-time detection of texture-less objects and estimation of their pose. It is the series of articles that ...
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71 views

Translation invariance in max-pooling and cascading with convolutional layer

I am reading through this page about convolutional neural networks and I am confused about the part about max-pooling (downsampling a signal/image with the maximum value in a block). Apparently, one ...
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2answers
78 views

Convex optimization in signal processing

In signal processing, convex optimization plays a useful role in problems such as sparse signal recovery and filter design. What other places does convex optimization appear? For example, in ...
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5 views

Is the same to calculate the Moments of an image using only its vertex?

The below image is a convex filled polygon, to calculate its moments we can resort to the Hu Moments and if the image is very big, this could be an expensive process. But if we use only the vertex can ...
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3answers
94 views

why the ultasound image is noisy by speckle noise?

My first question : I want to know why an image is noisy ?. why the ultrasound, SAR and Laser... images are noisy by a multiplicative noise not an additive noise? Another question : So the ...
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2answers
77 views

camera calibration: why chessboards?

Chessboards are very frequently used for camera calibration, this website also talks a bit about why: wiki. One of the reasons is, that chessboards define many natural interest points. Now my (very ...
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1answer
38 views

How to estimate radial distortion from lens characteristics?

Is there a way to estimate the radial distortion coefficients without calibration, given the lens characteristics, such as its diameter and its focal length? Typically for camera calibration a ...
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2answers
45 views

How to find the actual size of an existing object from the pixels of an image?

I am quite new to vision and OpenCV, so forgive me if this is a stupid question but I have got really confused. My aim is to detect an object in an image and estimate its actual size. Assume for now ...
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32 views

Difference between video mosaicing and video stitching

What is the difference between video mosaicing and video stitching ,is this both are similar or is there any methodology difference?
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19 views

Use the line function commend matlab of PDE toolbox in image processing

I want to use the line new command of PDE toolbox as Matlab R2015a to restore a noisy image with gaussian noise. The PDE is : \begin{eqnarray} \nabla.(\frac{ \nabla u}{\sqrt{1+|\nabla u|^2}}) ...
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12 views

Understand about registration between spatial prior and original image

I am working in level set/active contour method using spatial prior information . The main papers that I am focusing:"Automatic segmentation of neonatal images using convex optimization and coupled ...
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2answers
70 views

Using SURF algorithm to match objects on MATLAB

I am trying to find the difference between two images, using Matlab. The classic built in function that Matlab provides for this is because the two images don't have the same dimensions (The objects ...
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1answer
53 views

Question about Difference of Gaussian (DoG) algorithm

I am recently learning about Computer Vision and I am having a trouble understanding Difference of Gaussian (DoG) algorithm. I get how the algorithm works in high level idea, but I am trying to ...
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8 views

How much does sub-pixel sampling affect depth resolution in stereo vision?

If I have 2 sets of camera-pairs, to setup 2 stereo vision systems. Setup 1: cameras have 2940x2940 pixel density Setup 2: cameras have 98x98 pixel density with 30x sub-pixel sampling to get same ...
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1answer
41 views

Camera calibration using multiple images

I am trying to get the hang of camera calibration. For this purpose, I have mainly watched this lecture on youtube: Lecture 12: Camera Model by UCF CRCV. I believe that I understood the main ideas: ...
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12 views

How does a system like Kinect determine the (x,y) location of point projections?

I'm designing a system that will project structured light onto an object in order to measure the distance between the object and a sensor -- much like xbox kinect! However, the most effective method ...
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1answer
60 views

difference between feature detector and descriptor?

I am new to feature detection and tracking. can anybody please explain in detail the difference between detector and descriptors. which among these are detectors and which are descriptors : Harris, ...
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12 views

Error correction in a video feed

How does one write software to minimize errors? As in, say I'm trying to look for contours in a region of interest. After writing down the program for contour detection, when I test it the contours ...
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2answers
161 views

relation between luminance and eigen values of an image

There are some research papers in the literature which apply Singular Value Decomposition (SVD) on an image to decompose the image matrix into U, ...
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1answer
28 views

Machine Vision - Infinity Focus effect

I am working on a research project that involves machine vision. The camera we are using implements infinite focus - I have been informed that this can affect the accuracy of computer vision ...
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3answers
46 views

Segmenting and labeling chessboards through computer vision

With almost no experience/knowledge in computer vision, I am currently trying to segment and label the separate squares on a chessboard (i.e. a1 ... h8). My goal is to use the information to ...
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109 views

Bounding box around text given a single point inside text using opencv

I am trying to figure out a way to detect a "best-fit" bounding box around a text, given a single pixel(or a small set of pixels) inside this text area. Consider the following image: Given the ...
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1answer
63 views

Metal Defect Detection

I am developing a machine vision project to find defects on metal surfaces. I want to learn and implement algorithms which commercial systems are use for metal surface defect. My sample object as ...
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1answer
34 views

what is the difference between HSV and CIE-Lab color space? [closed]

when do we use HSV color space and when do we use CIE-Lab color space?
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65 views

Identification of a given barcode as either 1 D or 2 D

I am working on an algorithm (in MATLAB) to identify/classify a given bar code (image) as 1 D or 2 D. I have considered using the contrast of THE IMAGE matrix as a parameter or using the FFT of the ...
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10 views

What is the relationship between the Harris corner detector and shape operator?

From my understanding, the Harris corner detector looks at the gradients in the principal directions of a small region. Why are the eigenvectors of the matrix the principal directions? More ...
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1answer
74 views

Finding aberrations and/or unknown features in an image

Is it possible to find unknown featues in an image or in other words aberrations from a normal image of some type? For example: Imagine you have lots of pictures of different faces, so all are ...
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1answer
149 views

How to learn image processing / computer vision in a practical way?

I am new to the field of image processing / computer vision and I find it very hard to get my hands on the subject. I read a lot about the basics/theory but I feel in no way able to use this knowledge ...
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55 views

pre-processing to improve feature detector before tracking

I am trying to make tracking for soccer player, I need to detect features from this player and then estimate the distance difference of these pixels over number of frames. first I have to detect the ...
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7 views

what is in intuitive explanation of local derivative pattern (LDP)?

Zhang et al. proposed the LDPs for face recognition . They considered the LBP as the nondirectional first-order local pattern operator and extended it to higher orders ( th-order) called the LDP. is ...
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8 views

what is the drawback of DLBP(Dominant local binary pattern)?

Although the DLBP features encapsulate more textural information than the conventional LBP features, they lack the consideration of distant pixel interactions. The reason is that the binary patterns ...
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21 views

How to implement extended structure tensor

I am implementing an extended structure tensor that defined as where (*) is convolution operator; K_sigma is a Gaussian kernel with standard deviation sigma. The subscripts x and y denote the ...
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16 views

SIFT - Lots of Hessians are not-invertible

I'm trying to code the SIFT algorithm. In the step of using Taylor series to find accurate locations of key-points, the number of key-points plummets from hundreds of thousands to fewer than 1000. ...
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1answer
129 views

Lane detection and tracking using B-snake?

I am truly sorry if my question sounds little bit stupid, but I am getting stuck at this part for a long time. I am currently working for my final year project of lane detection for curved road using ...
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34 views

Why is MRI more expensive than CT?

I am not asking how MRI scans are different from CT scans, but rather why they are more expensive. I know that CT scans take longer for starters, and am wondering whether this is essentially the only ...