MimSaad
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OpenCV: Can't find large rectangle contour
1 votes

My guess is you can find all rectangles using hough transform. OpenCV python returns a structure that has all rectangles. Then sort the rectangles and find take out the largest one and using the ...

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Can compressed sensing be used instead of intepolation for missing values?
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5 votes

Yes, at least in the above case it is possible. Though it might not be computationally as cheap as other methods such as least squares based curve fitting. I do not think injecting NaN gonna help, ...

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Compare feature vectors of an image in MATLAB
2 votes

As far as I understood you're seeking the best similarity measuring function. There are zillions of metrics for that purpose, in fact any clustering algorithm such as SVM, K-means and neural network ...

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Signal and Space/Time
4 votes

My understanding of your question is that you have a small misunderstanding here. In the definition it is not said time and space. A signal can vary in time or space. Some signals vary with time, as ...

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Sudden loudness changes producing unwanted noises?
1 votes

It is not only noise. It is noise and distortion because this scenario modulates the signal as well. Abruptly changing amplitude of a signal is equivalent to multiplying the signal with a rectangular ...

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$\int_{-\infty}^{+\infty} |G(f)| \,e^{j2\pi ft}df=|g(t)|$?
1 votes

Short answer, as a general rule NO, but depending on $g(t)$, in special cases YES, e.g. when $g(t)=0$ or $g(t)=Const$ ! Maybe if you find the Fourier of $Sign(G(f))$, e.g. $G(f)$ turns out to be ...

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Can a linear reconstruction in compressive sensing perform well?
0 votes

This is a good idea, I was pondering upon awhile ago. I drop some thoughts. A Linear(no activations) MLP with a single hidden layer performs the same or sometimes better than a Multi-layer model with ...

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Why calculate negative frequencies of DFT?
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7 votes

DFT does not decompose a signal into regular sinusoids, it decompose it up into complex exponentials. Therefore, the Fourier transform of a real value signal must be conjugate symmetric (has both ...

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Average value of power spectral density
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0 votes

You should remove low frequency content of the diagram. Simply use moving average filter. find the optimum filter size that produces your desired result. Here is a matlab example code. t=0:0.001:1; ...

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Can I decompose a sine signal into its component sine waves?
1 votes

Curve fitting is another option after Fourier transform, you can fit a sum of sine function to your signal and the fitting coefficients show the amplitude and frequency of the signal. Check this: ...

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Why is incoherence important for compressive sensing?
1 votes

It is necessary when reconstruction is considered. Simply imagine the case when $A = \Phi \Psi$ has a high coherence, e.g. all columns are exactly the same and indistinguishable, then there is no ...

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Sub nyquist sampling, required number of samples for time sparse grouped signals
0 votes

Compressed sensing does not assume any distribution of non-zero elements in the input vector (signal), so it makes no difference if your non-zero elements are near each other or located uniformly on ...

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How to unify the color and brightness measure of two given cameras?
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Histogram Equalization can help as well. It tries to have the same distribution of pixel values in both images.

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Is it possible to remove the non-random noise in the signal by averaging?
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The random does not play a role when averaging is used to remove the noise. The distribution of noise does. Averaging works when the mean of the noise is zero. The assumption is that averaging noise ...

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Why do we need deterministic measurement matrices in compressed sensing?
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3 votes

As far as I know there are two reasons: In sensing part: For practical implementation, usage of random matrices is hard, so people try to come up with simpler matrices that are fixed, this is thought ...

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Sensing matrix for compressed sensing
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3 votes

A sensing matrix maps input vector to measurement vector through linear wighted summation of input. What makes a specific matrix good, is application dependent. Now, both distributions more or less ...

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Single Pixel Camera - Compressive Sensing
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2 votes

First I explain how compressive sensing is leveraged into imaging reconstruction and then a little bit on how CS is deployed in an imaging hardware. Compressive Sensing For the sake of simplicity ...

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What are the practical constraints on designing Sensing matrix in compressed Sensing?
3 votes

Checking for RIP of a matrix is an NP-Hard problem which means it is not computationally feasible to accomplish. RIP is used in matrix design mostly in theoretical aspects. Stealing @David 's comments,...

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Gaussian pyramid: why needs the image to be downsampled
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1 votes

In the context of a Gaussian pyramid, why is the image down-sampled separately although the numbers of pixels are decreased through smoothing already? After filtering the image the number of pixels ...

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PSD using MATLAB's $\tt pwelch$ algorithm window length and measure units
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0 votes

Regarding your questions: Is there a good rule of thumb for determining the length $L$ of the sections (second variable for the function)? $L$ (or window argument) specifies a window function to ...

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Clock Jitter and Phase Noise
1 votes

There are two sources of sampling jitter in ADCs namely clock jitter and sampler jitter (S/H circuit). Clock jitter or clock phase noise is due to clock imperfections. So if you have an idea sampler, ...

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Is it theoretically possible to perfectly quantize a continuous signal?
4 votes

I'd like to point out Heisenberg Uncertainty principle, based on which theoretical achievable precision is limited. It states that one can not measure two complementary qualities (e.t. here time and ...

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Harris Corners Detector squared derivatives
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1 votes

I think this part in article is starting point of the confusion : See how the $I(x+u, y+v)$ changed into a totally different form $I(x,y)+ uI_x + vI_y)$? The author should have write a bit more ...

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linear-expansion filter for image (2D array)
0 votes

Simply resize the binarized image to a larger image but do not use any high order interpolation in resizing and instead use 'nearest neighbor'interpolation technique. In MATLAB: im2 = imresize(image, ...

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Find common features across images
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0 votes

If by feature you mean a group of pixels (like Goofy) I suggest to try SIFT + SVD. (http://weitz.de/sift/)

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Different representations of frequency space of 2D image FFT
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1 votes

The second image you find online as you mentioned is magnitude and the first image must be either real part or the imaginary part (but not both). If you calculate complex value magnitude for each ...

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Detecting the rotation of digits in an image
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2 votes

You can use Hough Transform to find dominant lines in the image and then based on rho & theta parameters of the Hough transform, align your text. First you need to remove unnecessary details from ...

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Real time FFT & IFFT with low pass filter
1 votes

The sharp peaks are actually due to segmentation and concatenation, you need to have overlapping segmentations. The peaks occur on the edges of segments mostly. In following figures I tried to show ...

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Can Convolution neutral network train(learn) separately (train different times)?
0 votes

This is called curriculum learning , and not only this approach is possible but also it is shown to be quite effective. A few years ago I also came up with similar idea. Basically the idea is, instead ...

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Quantization error in sampling
1 votes

From your question it is unclear what is the dynamic range exactly, or is it needed to normalize the signal or not? Anyway, I assumed it to be normalized (since somehow this happens in ADCs). To ...

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