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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16 views

What after image segmentation? [on hold]

I've read about different techniques to segment images. I tried the segmentation technique which involves clustering features extracted from a depth image (which includes position, color, depth). I ...
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10 views

Gabor Filter implemetation in frequency domain with three different filter central frequencies and 4 orintations

I am trying to construct a Gabor filter with 3 different central frequencies and 4 different orientation. But for a particular frequency, for all the orientation I am getting the same response, I don'...
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1answer
39 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
35 views

The difference of downsampling an image and smoothing an image?

I am, at the moment, trying to read up on some simple computer vision elements, in which i have become a bit comfused on the terms downsampling and smoothing, and whether there is a difference between ...
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11 views

ASIFT does not appear to simulate all required possible views

ASIFT is an extension to SIFT to make it affine invariant. http://www.cmap.polytechnique.fr/~yu/publications/ASIFT_SIIMS_final.pdf According to the picture above, ASIFT algorithm is only sampling ...
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13 views

How to use Mikolajczyk evaluation for detectors/descriptors?

I want to compare different detectors/descriptors (both binaries and not) for my application and I want to use the Mikolajczyk evaluation framework, which is became a standard in the community about ...
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1answer
23 views

Point cloud comparison

Let me preface this question with the fact that two hours ago I had no idea what a cloud point was. I do however have a solid mathematical background although geometry has never been my focus. I do ...
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2answers
21 views

How to calculate to structure tensor?

Structure Tensor is a matrix in form: $S=\begin{pmatrix} W \ast I_x^2 & W \ast (I_xI_y)\\ W \ast (I_xI_y) & W \ast I_y^2 \end{pmatrix}$ where $W$ is a smoothing kernel (e.g a Gaussian kernel)...
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1answer
52 views

Detecting sloppy hand-drawn arrows in images

How can I easily and efficiently detect hand-drawn arrows and their directions from an image? They're probably drawn lightly, with something like a pencil, on a piece of paper. If I had ...
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20 views

Detecting objects in real world video feed?

I have an image which consists on an object in a plain black background. This is the reference image of the object. Now, My task is to take a webcam and obtain the video feed and I have to detect if ...
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10 views

looking for simplified version of motion capture for simplified situation where objects are solid and have no joint (no internal degree of freedom)

The whole question is about a simplified algorithm for tracking a single solid object which has no joint, with assumption that i have full control on adding some markers in real world to it. For ...
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12 views

Is there an optimal range for Pratt's Figure of merit?

I am working on a new edge detection method. However, when I tried to evaluate it based of FOM values, I got really small values, though my algorithm's performance is good comparatively. What I ...
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1answer
24 views

How should calibration points be distributed?

I do camera calibration for a single camera with a chessboard pattern in opencv for the first time. The focus is fixed. I'm not sure how to do it, there seems to be many questions: How many images ...
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12 views

Point cloud color blending after registration

I have succesfully registered two point clouds of the same scene obtained from different camera positions. Color values are different due to changes in light condition between both positions. I would ...
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1answer
50 views

Kalman for 3D position and 1D orientation

Is the following state correct for a Constant Acceleration (CA) model KF applied for tracking an object which moves in (x, y, z) and have the freedom of rotation $\phi$ around the $z$ axis? \begin{...
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1answer
60 views

Which is correct representation for function of variable?

I have a function as $$E=\int_\Omega -\log\big( p_i(x)\big) dx$$ where $p_i(x)$ is density distribution which estimated by Parzen window method. $$p_i(x)=\frac{1}{\Omega_i} \int_{\Omega_i}K_\sigma\...
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2answers
77 views

Segmentation of small artifacts - Image Processing

I am working on a task of segmenting small artifacts from a set of images like below: I am looking for a generic approach, but unsure of what to search? I tried looking at density flow analysis, but ...
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12 views

Implementing Markov Random Field

I want to implement MRF for stereo vision.But I am a bit confused about the theory of the Belief propagation network. I create a graph, where nodes are the pixels and edges connect neighboring pixels. ...
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113 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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15 views

Computer vision - What is the difference between appearance based and feature based in object recognition?

As English is not my first language, I have a little trouble in understanding these terms. I hope someone can explain this to me (if possible, in a simple to understand way). Plus, is there any other ...
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1answer
72 views

How to calculate particles sizes for spheric particles with overlapping and superposition? (Example image included)

I'm trying to automatically calculate particles sizes histogram for images like this one: Common threshold and segmentation doesn't seem to work. What filters and algorithms do you suggest to be ...
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3answers
51 views

How to filter objects on basis of orientation of regionprops

I am trying to detect straight vertical lines in an image. I used vertical edge detection and then I tried to check which objects has the ...
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2answers
133 views

Can deep neural networks achieve real-time video analysis?

Recently, convolutional neural network based, deep architectures (DNN) such as AlexNet and VGGnet have been very successful in image classification challenges (e.g. ImageNet) and action recognition/...
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1answer
35 views

Finding crosses and their orientation on a given image

I want to recognize table structure from some arbitrary photo image and store it in some formal notation (Let it be HTML table notation). For example I have this blurry image as input: After ...
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9 views

Body Part Estimation from multiple depth images with occlusions

The is a number of works on the problem of body part estimation and it has widely been acknowledged that depth information helps in the problem. Most approaches I have seen so far work on the depth ...
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2answers
64 views

Image distortion and alignment on 3D mesh / pointcloud

Currently I have a fairly accurate (50 µm) and large dataset from a 3D scanner and a set of high resolution pictures. Sadly the 3D scanner (a Nikon/Metris arm-based CMM that was hanging around the lab)...
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55 views

Estimate camera generalized velocity from consecutive frames

Let's suppose I have a camera which can move freely in 3D space and has 6 degrees of freedom. Is it possible to estimate the linear and angular velocity of the camera from 2 or more consecutive frames?...
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16 views

Which kind of noise will show benefit with Guided filter

I am using guided filter function in MATLAB img_filtered = imguidedfilter(img_noise) I knows that guided filter is very good to preserving edge in noise image. ...
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1answer
100 views

What is different between gradient and imgradient functions in MATLAB

I would like to compute the gradient of an image I. I have the following two options : [Gx, Gy] = gradient(I); g = sqrt(Gx.^2+Gy.^2); or ...
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21 views

Retrive texture / data from photos of sphere object

I've built a photo box for taking photos of spherical objects (balls etc). I take photos cubical from six different angles. Now I want to extract the bitmap texture from the object with most ...
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21 views

How can a medical doctor use the information given by someone working in medical image computing(shape analysis)? Details follow

Posted also here, where it's been put on hold. I did modify it afterwards though. http://biology.stackexchange.com/questions/43997/how-can-a-medical-doctor-use-the-information-given-by-someone-...
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2answers
75 views

How to approach detection of anomalies in a video feed?

As part of a project I have a video from a quadrotor that captures the road and the environment around it and I want to identify and detect potholes and speedbumps on the road using image processing. ...
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1answer
53 views

Generate a nonuniform illumination (bias field) 2D image

I am creating a nonuniform illumination in MATLAB R2015. The nonuniform illumination (known as bias field) is defined as Nonuniform Illumination (intensity inhomogeneity) which manifests itself as ...
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1answer
67 views

How do I understand Fourier descriptors more visually and intuitively?

I read the book Image Processing, Vision and Machine Vision and find the concept Fourier descriptors hard to understand, although literally its derivation is somewhat reasonable. Can anyone give me a ...
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1answer
67 views

Good example for comparison between Guided and Gaussian filters

I am looking for a good example that showing the different between Guided and Gaussian Filters. The example need to show the benefit of Guided filter, (for example: preserving edge...). Could you give ...
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2answers
57 views

Seeking segmentation methods for this light microscope image

Although I am not new to math or programming, I am a total newbie to image segmentation. I have the following light microscope image and I would like to segment it into cytoplasm (the magenta ...
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32 views

Object localization down to the pixel

I am somewhat confused on the terminology used in Computer Vision. Suppose I wanted to detect (localize) an object (say, a human) in an image. However, a box around the human is not sufficient, what I ...
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1answer
40 views

Confusion regarding Sobel operator

I am taking computer vision course, where I learned about Sobel operator for detecting edges. I somewhat understand how it works as described here. But I have a basic confusion. The operator can be ...
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56 views

How to choose the threshold in uv disparity?

Several papers on uv disparity or v disparity state that once the uv disparity maps are computed a threshold should be applied. For instance in Alexandru Iloie UV disparity based obstacle detection ......
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29 views

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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65 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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67 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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11 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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27 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
95 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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1answer
68 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
31 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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101 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 axis-...
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1answer
45 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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24 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 ...