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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Support Vector Machine is unable to recognize the digits in images properly

I am training a SVM on MNIST Handwritten digits database to make a basic digit recognizer. It is able to recognize digits easily on some standard images I took from a source. I then captured an image ...
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33 views

2D Convolution Along Only One Axis and MATLAB Implementation

I'm trying to implement a Depth Map algorithm for Light Field images and I stumbled in a 2D convolution of an image and a kernel, but I think that the convolution is only preformed along the x axis. ...
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43 views

How to match a thumbnail to an area in the original image?

Suppose that you have a thumbnail and the original image from which it was generated. You need to match the thumbnail to an area in the original image that represents the original selection from which ...
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5 views

How can I use a trained model to generate related images?

Suppose I have a data set of a large number of related images and I extract HOG features and train it using SVM Classifier or KNN Classifier. How can I use this model to generate a new image which is ...
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18 views

image processing: identifying connected regions based on regions' moments

Assume that I have the following grayscale image: and given that I have, for every segment of the different intensities (i.e. 1 black region with intensity 0, 1 gray with intensity 1 and 4 white ...
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1answer
22 views

NORM_HAMMING2 vs NORM_HAMMING

I'm trying to use ORB features with a cv::BFMatcher. ORB is based on binary descriptors so HAMMING must be the choice, but I'm not sure I understand the difference ...
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8 views

Extracting DCT coefficients from H.264/AVC bitstream

Is it possible to extract DCT coefficients from H.264/AVC bitstream without doing a full-decoding of the video? There are a lot of papers on compressed domain video processing which are based on the ...
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1answer
24 views

How the noise in time series can be reduced?

I have asked the question in the following link: Are time series data always contain noise? I wonder if we could use variational methods to denoise the time series data just as in computer vision? ...
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33 views

How to find the largest empty rectangle using OpenCV?

I need to find the coordinates of the largest empty rectangle in a PNG image. The rectangle should consist of light colors (if that is too difficult, white pixels only are fine) and should be ...
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1answer
32 views

Low Pass Filter - pixel correlation

I am trying to understand low pass filters for image processing, I came across an article that stated that low pass filters effect noise more than the real data due to that the image Noise always ...
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21 views

What techniques exist for segmenting particles given a priori knowledge of the particle size?

I am attempting to segment the following image, which consists of several circular particles that are surrounded by fringes. My goal is to create a mask that is black where a particle is located, and ...
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1answer
26 views

Can I segment characters from this image with CSV?

I am trying to segment my characters on this image with using column sum vector. This method actually works on the paper I've read about license plate recognition. it looks useful for my images ...
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1answer
53 views

How can I approximate a signal

I have a signal as the below figure. I am looking for some schemes to approximate the signal. I have found some ways for that task: Using basis function (polynomial) to approximate the signal ...
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1answer
13 views

camera calibration change orientation of axis

I want to solve for the extrinsics by using direct linear transformation on corresponding 3D LIDAR points and 2D camera points. I already have the intrinsics. Problem is, points behind the camera ...
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12 views

Essential Matrix from line correspondences

I'm looking for some library with a function to compute an essential matrix from line correspondences in multiple images. All the computer vision libraries I know use point correspondences to compute ...
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0answers
11 views

How is per-class rate defined?

I've recently read the following For our pixel labeling, consistent with [20], we report the number of pixels correctly classified (per-pixel rate) and the average of per-class rates. The ...
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1answer
20 views

Getting composition of a mixture of colours

I wanted to validate a thought on blending of colours digitally. Imagine I have two colours, $C_1$ $(R_1,G_1,B_1)$ and $C_2$ $(R_2,G_2,B_2)$. Now, I create colour $C3$ as follows: $C_3 = \alpha C_1 + ...
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36 views

Converting from RGB to Lab to reduce colors

In many papers I see the following: First we have to convert image from RGB to Lab color space to reduce colors then ...
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1answer
15 views

How does the PASCAL VOC challenge evaluate the task of object detection?

I fail to understand the evaluation parameters like true positive, false positive and false negative in detection and classification tasks. can anyone help me to figure out what does each of these ...
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18 views

How to derive distance on flat floor to object in single camera image

With reference to the comment by @ Andrey Rubshtein in Is it always necessary to use two cameras to find the distance between camera and object? Another way is when you are located on a flat ...
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8 views

Training an object detector using “object present/absent” labels on image

I want to know the generic name for this technique of object detection: You're given a set of images labeled as "containing a cat" or "not containing a cat", and with this information you train a ...
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2answers
31 views

Background averaging not working

I'm working on a problem where I'm trying to use background averaging to see what the frame looks like in a beehive behind the bees. I've been trying to use standard averaging (I take an image every 1 ...
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11 views

Normalizing points gives worse result in DTL algorithm than no Normalizing

I am trying to find a homography for this images: I have to give a set of 10 points correspondencies between the two images. Then, I apply the DTL algorithm To find the matrix ...
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1answer
132 views

Rotated object detection by Viola jones Algorithm

In my project I need to detect rotated and non-rotated faces in real time. I read original articles and try to use common implementation in matlab and openCV. And as I understood Haar features are not ...
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18 views

Feedback Loops for Computer Vision

What image shape-detection algorithms exist that look in the neighborhood of starting parameters, rather than trying to find the "best possible fit" for image. For instance, I'd give a starting ...
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12 views

variattional calculus based 1d denoising

As of speaking about 1 d discrete denoising via variational calculus; I would like to know how to manipulate the length of smoothing term as long as it should be N-1, while the length of data term is ...
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2answers
59 views

Magnitude of Sobel filter result, vector or scalar?

I have a question about image gradient magnitude, given an image $I$. The horizontal and vertical derivatives resulting from Sobel filters are defined as: $$K_x= \begin{bmatrix} -1 ...
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2answers
54 views

How to represent a given equation more clear, profressional and short form?

I have a image $U_{m \times n}:\Omega \to \mathbb R^2$, the output $P$ can be define as $$P=\mu J_{m \times n} - U$$ where $\mu = \max \{ u_{ij} : 1 \leq i \leq m, 1 \leq j \leq n\}$, $J_{m \times ...
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24 views

Application of BIC, MDL, AIC

I understand that mathematical motivation behind Bayesian Information Criterion (BIC), Minimum description length (MDL), Akaike information criterion (AIC) are different but I am assuming that there ...
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4answers
3k views

Is deep learning killing image processing/computer vision?

I'm looking forward to enroll in a MSc in signal and image processing, or maybe computer vision (I have not decided yet), and this question emerged. My concern is, since deep learning doesn't need ...
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14 views

Doubt about the LFW‏ database

I post below a part of the mail I wrote to the creators of the database LFW: i am currently working on a face recognizer which has given me very good results in small tests performed, now i would ...
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48 views

Question about SURF - speeded up robust features

I am trying to get my head around the SURF detection method (fast hessian), but I have run into some problems. I have only just begun to look at it, so I apologize for any "ill" asked questions. I am ...
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37 views

How can i implement Brisk keypoint detection in FPGA?

I want to implement Brisk key point detection on hardware(FPGA). I read about it in the "BRISK: Binary Robust Invariant scalable Key points" by Stefan Leutenegger, Margarita Chli and Roland Y. ...
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17 views

Designing 2D DFT filter that works with cycle per degree

Here is my question regarding 2d dft. I know how to do 2d-dft and convolution and filtering. However, I still have a basic question. Maybe I have not understand the concept, and that's why I don't ...
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26 views

How is a Sim3 lie group used to project a 3D point?

I have a $Sim3$ transformation with scale, rotation and translation that describe the camera to world transformation. How can I use it to transform a point in world coordinates to camera coordinates? ...
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33 views

What is the difference between a range image and a depth map?

https://en.wikipedia.org/wiki/Depth_map https://en.wikipedia.org/wiki/Range_imaging To me, it sounds like they are the same thing, except depth map implies only having the z coordinate info. But ...
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1answer
62 views

Object detection using several images

how do people combine different information (e.g., RGB and depth image or RGB and thermal image) to make their object detection algorithms better? If the single modality images A and B are perfectly ...
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1answer
77 views

Computer vision, Coupon code detection, sugested algorithms

The telecommunication operator in my country has coupons that used to recharge the balance I want to develop an Android application, that with the camera can take the scratched number and recognize ...
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1answer
33 views

Converting blobs to circles

I have this binary image with some blobs of random sizes. I would like to convert the blobs into circles of uniform diameter. it doesn't really matter what diameter but they need to be circles and ...
2
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1answer
29 views

Why is this projection wrong?

I am trying to figure out why a 3D cube doesn't project in the right place in the image. I start with the camera at origin and the cube centered at (0,0,1) world ...
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45 views

Content-based detection about where a picture was taken

I'm searching for a solution to detect where a picture was taken inside a geographical location. I can imagine either of two scenarios: either a picture is taken from afar, encompassing the whole ...
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1answer
48 views

What is an approach in computer vision that can be used for tracking players in hockey games?

It differs from human tracking in random environment in that detail that we have fixed environment. And players move pretty fast and it is important to resolve collisions and occlusions, keep track of ...
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13 views

Diffeomorphic Mapping

I saw this term several places while reading some computer vision papers on brain mapping. But could not understand the term clearly. What are the properties of diffeomorphic mapping? Why its so ...
2
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1answer
34 views

How are the scaling parameters included (extracted from) an essential matrix?

An essential matrix relates corresponding points between two images assuming that a camera satisfies the pinhole camera model, and can be expressed as: $$E=K'^TFK$$ where K is the calibration and F ...
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2answers
47 views

Calibration (intrinsic) parameters of a virtual camera with some known information

I need the calibration matrix of my simulated camera, I am trying to fully comprehend and follow the steps from Step by Step Camera Pose Estimation for Visual Tracking and Planar Markers as well as ...
2
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1answer
62 views

Obtain motion between image features by means of the homography matrix

I have been reading several really good answers about how to obtain camera pose (rotation, translation, etc), such as this one and this one, but I am not sure how this applies to my problem. My ...
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2answers
115 views

Can disparity range from negative to positive values for parallel cameras?

In my stereo-rectified camera pair (not physical, but two positions of the same camera), when I project some 3D points in both images to find a rough disparity range, I often get a range that goes ...
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26 views

how to compute horizontal angle of a pixel from a computer vision camera

My program needs to compute the angle of a pixel from a computer vision camera that has 120 degrees field of view, and resolution of 640 pixels wide and 480 pixels high. Program receives an X,Y array ...
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91 views

texture matching between patches of an image

I have an image A which I have divided into 4 x 4 subband images. For a given patch P1 in ...
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70 views

Which way the whale is moving

I am trying to find out which way the whale is moving. So I have an image of the whale swimming in the water and I want to find out where is it located and which direction does it swim (with respect ...