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1answer
19 views

generating white gaussian noise in matlab using two different functions

I want to know the difference between the two Gaussian noises generated below? Which one is white and how can i make the other one white? y=wgn(1,10000,0) and ...
0
votes
1answer
14 views

Derivative of equation containing Gaussian filtered image

Let $w$ be our image. For example, consider the following with the vectorized $w$: $$ E(w) = \frac 12 \|Aw+b\|_2^2 $$ I know the optimal condition of the above equation: $$ \nabla_wE = A^TA\hat w + b ...
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0answers
12 views

Analytical expression for salient Blob detection in scale space

I am working on exact mathematical expression which can be obtained in image processing tasks.(I do not know much about image processing but my work is more mathmatical) In Gaussian scale space, we ...
3
votes
1answer
59 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} ...
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0answers
42 views

Resources on Non-Gaussian Channels

I understand why most of the classic textbooks only consider Additive White Gaussian Noise channels in digital data transmission. Unfortunately in my case noise is not Gaussian and it might even be ...
0
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1answer
35 views

Determinant of Hessian approximation (SURF)

I have a question regarding formula in SURF article by Bay et al. Theory Given a point $p=(x,y)$ in an image $I$, the Hessian matrix $\mathcal{H}$ in $x$ at scale $\sigma$ is defined as follows $$ ...
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0answers
33 views

What does the output of Gaussian Mixture Model (GMM) represents in a HMM-GMM based speech recognition application?

Till now I know that- first the speech is converted frames and feature vectors are calculated for each frame using MFCC. And while training the Acoustic model- HMM model is generate for each phoneme ...
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2answers
33 views

Finding Argmax in MATLAB [closed]

I have a Gaussian random variable $z$, whose mean $\mu$ and variance $\sigma^2$ are functions of two variables $x$ and $y$. Is there any way in MATLAB so that I can find the values of $x$ and $y$ for ...
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0answers
22 views

Approximate LoG using DoG

I read in Lecture 11: LoG and DoG Filters (Robert Collins) that the Laplacian of Gaussian (LoG) can be using a difference of Gaussians (DoG) and that it is best approximated when $\sigma_1 = \sigma / ...
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0answers
44 views

Fourier transform on Scilab of a Gaussian function

I am trying to do a fourier transform on Scilab, of the Gaussian function $y(x)=\exp(-\frac{x²}{2})$, by using the fft command. So I plotted the graph of ...
0
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2answers
32 views

What does it mean by “Adding Gaussian Noise to a 2D Image”? [duplicate]

As far as I understand, Suppose, we have a 2D image of pixel resolution 200 x 300. That means, the image has 60000 pixels in it. Now, we would generate $n$ random values and add those values to $n$ ...
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2answers
638 views

Why is Gaussian noise called so?

Can you please explain: why is a specific type of noise called "Gaussian noise"? Why is it relevant to call it Gaussian? Please, explain in layman's terms.
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2answers
22 views

Is there any transformation to exploit the sparsity of a Gaussian Wave?

I am looking for a transformation in which the gaussian wave when transformed with a particular analysis function would make the energy contents be mostly present only in a short band of frequencies? ...
0
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0answers
15 views

Reduction of Sample Size of a Gaussian Pulse

I need to sample a gaussian wave of pulse width of 1 us which is being modulated by a cosine wave of GHz frequency. The different cases that I am interested in are 1) The initial phase of the cosine ...
0
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0answers
35 views

Why does increased kernel bandwidth equate to increased SNR values?

If I apply a Gaussian Kernel to an image with some noise applied to it and I want to remove that noise, why does the Signal to Noise Ratio increase as I apply kernel's with higher and higher sigma ...
0
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1answer
33 views

2D Gaussian Seperation into 1D Gaussian components

I have been reading this http://homepages.inf.ed.ac.uk/rbf/HIPR2/gsmooth.htm and I am having trouble to perform the seperability. So I kinda did it in paper. Lets say y Gaussian function is G(X,Y), ...
0
votes
1answer
54 views

Double Integrating Gaussian Noise

My question has to do with integrating gaussian noise. Let us assume we have samples of discrete gaussian white noise with mean $\mu = 0$ and variance $\sigma_{th}^2$. These noise samples are passed ...
1
vote
1answer
62 views

what's gaussian noise look like?

I am using Matlab function imnoise to add gaussian noise to one image. However, it seems that adjacent samples of the noise is correlated. I am using matlab code below to add noise. ...
0
votes
1answer
54 views

Gaussian wavelet generation of a given frequency

How can I generate a Gaussian wavelet (time domain) with a given central frequency. I mean, if I take the Fourier Transform then its spectrum should be around that given central frequency. For ...
3
votes
1answer
77 views

Is $A\cos(\omega t+\theta)$ a Gaussian random process?

$Z(t) = A\cos(\omega t+\theta)$ where $A$~$N(0,\sigma ^2) $ and $\theta $~$(0,2\pi)$ are independent. I'm trying to figure out if $Z(t)$ is a Gaussian random process and whether it is strict sense ...
0
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0answers
33 views

Gaussian signal / image smoothing at sigma 0.5

I am currently reading up on Lowe's paper [1] on SIFT keypoint detection. On the page labeled 97 he mentions We assume that the original image has a blur of at ...
0
votes
1answer
30 views

Gaussian filter in terms of pixel radius

So I'm writing an app that blurs and downscales large quantities of images, but all the image processing libraries I've come across define gaussian blurs in terms of sigma and kernel size rather than ...
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2answers
89 views

what is a Gaussian signal?

I am learning Wiener filtering for 2D images by myself. From one book, it reads It should be noted that the study of the more general problem of signal denoising dates back to at least Norbert Wiener ...
1
vote
1answer
54 views

Implementing a 1-D Kalman Filter Regression, Missing the smoothing action (getting the opposite)

I am implementing the 1D Kalman Filter in Python on a fundamentally noisy set of measurement data, and I should be observing a large amount of smoothing...but, instead, my Kalman Filter is doing the ...
0
votes
1answer
35 views

How do I calculate the autocorrelation of a train pulse having only the pdf?

I have a pulse train of a fixed period, but a random amplitude following a Gaussian distribution $(\mu=0,\sigma=1)$. I know how to work with a random period or delay, but how do I proceed to calculate ...
0
votes
1answer
45 views

How to make a 2D gaussian Blur terms?

I want to make a 2D gaussian Blur coeffients. Now I am making 1D gaussian Blur term as following. ...
1
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0answers
17 views

Curve fitting to distorted Gaussian

I have to measure the distance between two pulse trains, each of which looks like a slightly long tailed Gaussian distribution. Is there a relatively easy curve fitting method for this? I can do it ...
1
vote
1answer
49 views

Mutual information of $ \infty $-PAM

I'm trying to compute using matlab the mutual information for an $ \infty $-PAM input (the limit of a very dense PAM constellation) for a range of snr and I got stuck. I'm working with a real-valued ...
0
votes
0answers
29 views

Calculating 3x3 Gaussian kernel

I have problems understanding/calculating one particular question in my exercises. This is the exercise: I know a) and I believe b) to be $[0.950, 1.33[$ c) is where I am currently stuck. I guess ...
1
vote
1answer
44 views

How to derive the $\log$ of fraction of two Gaussian distribution

I am designing a function $A(x)$ that map $x\to \{0,1\}$. The function $A$ can be expressed as $$A(x)=\begin{cases} 1 \text{ if $p_1(x) \ge p_2(x)$}\\ 0 \text{ otherwises} \end{cases} $$ where ...
0
votes
0answers
109 views

OpenCV's BackgroundSubtractorMOG algorithm parameters

Does anyone know what the history and number of Gaussian mixtures do in the Gaussian Mixture-based Background/Foreground Segmentation Algorithm used in OpenCV? I'm trying to optimise a background ...
1
vote
1answer
18 views

What is the equivalent smoothing function to running the same Gaussian 8 times?

Suppose there is an image which is to be smoothed by convolving it with a Gaussian kernel with standard deviation $\sigma$. If the image is then smoothed with this kernel 8 consecutive times, is the ...
0
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0answers
39 views

Implementation of HMM with continuous emission

I have a classification problem that, based on continuous features from a 1D signal, should classify to a finite amount of stages (discrete). There is a temporal evolution in the signal, so I am ...
0
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1answer
34 views

How will a Gaussian Blur affect Image Variance

I am trying to find a way to analytically estimate how the noise (or variance in pixel values) will be affected for a zero-frequency image of random noise after applying a Gaussian blur. In more ...
0
votes
1answer
47 views

Uniform quantizer for gaussian input signal

I have a gaussian signal $x$ with zero mean and unit variance. I am quantizing it by using a uniform quantizer of step size $q$ calculated by $$q = \frac{x_\mathrm{max} - ...
0
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1answer
40 views

Plotting uniform and Gaussian random variables

I want to create uniform and Gaussian (normal) random variables in MATLAB via rand and randn syntax. And I would like to plot ...
0
votes
1answer
65 views

What is the most efficient way to perform Gaussian blurs for varying sizes of Gaussian kernels in an image?

I have detected corner points of images using Harris corner detector in GLSL and now, I intend on using Fast Retina Keypoint(FREAK) as keypoint descriptor to later match the keypoints between images. ...
0
votes
2answers
25 views

How does gaussian convution stacking work?

If I first convolve an image with a Gaussian filter with σ = 1, and then convolve the output of that image with a Gaussian with σ = 2 Does this give the same effect as convolving the original image ...
1
vote
1answer
47 views

Multiscale Shape and Detail Enhancement from Multi-light Image Collections

I have been working on a practical implementation in Matlab of the algorithm Raanan Fattal suggested in the following paper. I couldn't understand the meaning of eq. 11 on page 5: g is a gaussian, ...
1
vote
1answer
77 views

How can I implement image widowing in my image in Java?

My initial image is a medical image and my main objective is finding directionality. The original size of my image was 8X8 and I have rescaled the image to 32X32 to increase my accuracy. My input ...
1
vote
1answer
61 views

Power spectrum of downsampled image

I am not sure if this is the right stackexchange community for this question, but here goes. I am generating a Gaussian Random Field (GRF) of a pre-defined power spectrum. In the image below, the ...
2
votes
2answers
175 views

gaussian filter close to image border

When applying gaussian filters close to the borders of an image, algorithms usually zero-pad or replicate/mirror/wrap the borders. This is not good enough for my case, so I wonder if there is ...
1
vote
2answers
70 views

equations to calculate coefficients of recursive IIR Gaussian blur filter

I am reading the implementation of IIR Gaussian blur filter from this link. In the source code, the coefficients are generated by the following code ...
0
votes
0answers
174 views

frequency response of Gaussian filter

In Matlab, the function freqz can produce frequency response in terms of transfer function and the function freqz2 can produce frequency response for FIR filter. It seems that I can's use the input ...
1
vote
1answer
60 views

Complex Gaussian Channel + AWGN noise

If I define a channel to have complex Gaussian coefficients, do I still need to add noise to the signal passing through this channel using the command "awgn" or would that be redundant?
1
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5answers
187 views

filter coefficients to know high pass and low pass filter

Looked on few questions already there in dsp.stackexchange and couldn't get the direct answer. Basically I have a kernel of a gaussian separable filter. ...
0
votes
0answers
14 views

Questions about channel modeling

I'm trying to model a statistical wssus channel using data collected from a ray propagation simulator. These are the following information I know : - 4 taps - each tap has 8 samples - each sample has ...
1
vote
1answer
880 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 ...
0
votes
1answer
119 views

Downsampling and Gaussian filtering in the context of scale space pyramids

In the context of scale space image pyramids using Gaussian filters I noticed that it's common to downsample the image after blurring with $\sigma = 2*\sigma_{init}$ . My question is: What is the ...
0
votes
1answer
84 views

Gaussian in matlab

I have written a function that implements a gaussian filter. I use fft2 to transform my image and my filter to 2d fourier transform. Then I multiply them and then use ifft2. The resulting image is ...