Questions tagged [multi-scale-analysis]

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What is the difference between single scale and multi scale?

My question is about the difference between single scale and multi scale in scale space theory. But I think I have to write what I understand about scale space theory and what I guess is the ...
hasanghaforian's user avatar
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1 answer

Clarification of some known issues in monocular visual odometry

so I'm reading an academic paper about some state of art algorithm of VO using deep learning, and there are some "known" issues of classical computer vision approaches that the authors bring ...
Ilya.K.'s user avatar
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Alternatives to Meyer Windows as Curvelets?

I am looking for alternative to Meyer window functions (Section 4.1) from which one can define a curvelet system. Are there any similar window functions which would be as easy to implement?
stish's user avatar
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Correctly scaling FFT of different lengths

I have been looking at using two FFTs of different lengths and displaying the output magnitudes on the same graph (a shorter length window for the higher frequencies, and a longer one for lower ...
samp17's user avatar
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3 votes
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At what stage do we compute the approximations and details while performing a DWT?

$$ \int_{-\infty}^{+\infty}{f(t)\psi_{j,k}^\ast(t)dt}\ \textrm{with}\ \psi_{j,k}(t)\ =\ a_0^{-j/2}\psi(a_0^{-j}t\ -\ b_0k) $$ If this is the expression for the wavelet transform, how does this lead to ...
Dhanush Giriyan's user avatar
7 votes
2 answers

Losslessness of Laplacian Pyramid

I was just reading up on the Gaussian pyramid and the Laplacian pyramid, used in compression applications of image. The source is here - Carnegie Mellon 16-385 Computer Vision - Spring 2019, Lecture 3 ...
Sridhar Thiagarajan's user avatar
6 votes
1 answer

2D Multi Scale Dot Enhancement Filter based on Gaussian Filter and Hessian Matrix

I'm trying to implement an algorithm that enhance dot and line like structures based on Hessian matrix, the algorithm uses Gaussian filter with different scales before calculating the hessian matrix ...
ZSmain's user avatar
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2 votes
1 answer

The Concept of scales in Gabor filter

I've been reading about Gabor filters, and there is a concept of scale. While I understand that Gabor features help in analyzing both the frequency and orientations of an image, what is the idea of ...
Curiosity's user avatar
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Is It Possible to Reconstruct the Original Image from Laplacian Pyramid?

In our computer vision course, my professor said we can reconstruct the original image from the Laplacian pyramid. It just feels to me that information is lost after doing subsampling and upsampling. ...
thyu's user avatar
  • 123
2 votes
1 answer

How Do Steerable Pyramids Work?

I'm reading a paper about texture synthesis using pyramids, and the very first section mention two methods for constructing pyramids, one is the Laplacian Pyramid (which I'm quite familiar with), the ...
user8469759's user avatar
1 vote
0 answers

Impact of Interpolation Types in Image Filtering (Laplacian Pyramids)

I am trying to construct Laplacian pyramids with different interpolation schemes such as bilinear, nearest neighbor, cubic and spline to observe the effect of interpolation types. I wrote a code in ...
Canberk's user avatar
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3 votes
1 answer

What Is Proper Paper and MATLAB Toolbox Describing and Discussing Wavelet, Ridgelet, Curvelet and Contourlet Transforms in Detail?

Question 1: Does anybody know any paper proper for getting started understanding the concept of Wavelet, Ridgelet, Curvelet and Contourlet transforms and their differences in detail? Question 2: ...
MJay's user avatar
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23 votes
3 answers

What Is the Difference between Difference of Gaussian, Laplace of Gaussian, and Mexican Hat Wavelet?

There are three techniques used in CV that seem very similar to each other, but with subtle differences: Laplacian of Gaussian: $\nabla^2\left[g(x,y,t)\ast f(x,y)\right]$ Difference of Gaussians: $ \...
DeusXMachina's user avatar
0 votes
1 answer

Energy Preserving Laplacian Pyramid

Both Discrete Wavelet Transform (DWT) and Undecimated DWT possess an important property of energy preservation: on each level $$\sum_i W_i^2 + \sum_j V_j^2 = \sum_k X_k^2$$ where $W$ and $V$ are ...
Andrey Paramonov's user avatar
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Band Limit in Gaussian Pyramid

In the paper The Laplacian Pyramid as a Compact Image Code, it says The pyramid algorithm reduces the filter band limit by an octave from level to level. How is the conclusion drawn? Is this related ...
Jogging Song's user avatar
2 votes
2 answers

Blending artifacts in OpenCV image stitching

I am using OpenCV to blend a set of pre-warped images. As input I have some 4-channel images (*.png or *.tif) from where I can extract a bgr image and an alpha mask with the region related to the ...
Finfa811's user avatar
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5 votes
1 answer

Multi Scale 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: \begin{equation}\...
ako's user avatar
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2D DWT Image Issue

In the literature, I see that a 2D signal can be transformed by first doing a 1D transformation on each row of the matrix followed by the same procedure on each column. It seems that $k^{th}$ level ...
Drew Cummins's user avatar
2 votes
2 answers

Can Aliasing Happen in Laplacian Pyramids?

I want to use the Laplacian pyramid framework for representing images. The The Laplacian Pyramid as a Compact Image Code's language seems to provide freedom in the choice of blurring/interpolation ...
user3246971's user avatar
6 votes
2 answers

Difference between Sub Sampling and Down Scaling of Images

I know that there are many ways to upscale (interpolate) an image using bilinear, bicubic, sinc... Somehow, these same algorithms can also be used to downscale an image. But when it comes to ...
Myath's user avatar
  • 163
1 vote
1 answer

Critically Sampled Laplacian Pyramid from 2nd Generation Wavelet

I'd like to know if a technique I have in mind is already used and has a name I can look up, and whether it is likely to work and be useful! My aim is to produce a discrete wavelet transform that is ...
Benjohn's user avatar
  • 347
10 votes
2 answers

Understanding SURF Features Calculation Process

So, I was reading the paper on SURF (Bay, Ess, Tuytelaars, Van Gool: Speeded-Up Robust Features (SURF)) and I can not comprehend this paragraph below: Due to the use of box filters and integral ...
motiur's user avatar
  • 414
3 votes
0 answers

Creating a Gaussian Pyramid

I'm trying to recreate a gassuain pyramid using the following scales: There seems to be two concepts used here: 1) When an image is halved, applying a gaussian kernel of σ will apply as 2σ. 2) When ...
JustinBlaber's user avatar
5 votes
2 answers

How to Combine Low and High Frequencies of Two Images in MATLAB?

I would like to combine two images A and B in the following way: 1) I want to take a Fourier transform of both of them 2) For image A I want to apply a weighted filter, which gives more emphasis for ...
jjepsuomi's user avatar
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1 vote
1 answer

Which Approach Is Better for Decomposing an Image into High Frequency and Low Frequency Components?

Which approach is better or there is mathematical justification for using Bilater filter and Fourier Transform to decompose a image into High Frequency and Low Frequency Component. Both Bilateral ...
Deepak kumar Jha's user avatar
22 votes
1 answer

How to Extract High Frequency and Low Frequency Component Using Bilateral Filter?

What does High frequency and low frequency component signify in an image. How to separate out the high frequency as well as low frequency component of an image using Bilateral filter.
Deepak kumar Jha's user avatar
5 votes
3 answers

Image Pyramid Without Decimation

I have an image processing algorithm which uses Gaussian and Laplacian Pyramid Decomposition. At each level of the pyramid the algorithm decimates the previous level by a factor of 2. The LPF the ...
Royi's user avatar
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