Questions tagged [multi-scale-analysis]

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Understanding Upsampling Filter in Laplacian Pyramid

For the construction of a laplacian pyramid, images are downscaled and then upscaled again. My question is what is a wise decision of the kernel mask for the upscaling task ? In more detail, lets say ...
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2answers
317 views

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. ...
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1answer
519 views

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 ...
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0answers
40 views

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 ...
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1answer
62 views

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: ...
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2answers
12k views

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: $ \...
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1answer
77 views

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 ...
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1answer
205 views

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 ...
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2answers
4k views

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 ...
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1answer
491 views

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 ...
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2answers
303 views

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 ...
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2answers
1k views

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 ...
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1answer
96 views

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 ...
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2answers
10k views

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 ...
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0answers
2k views

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 ...
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2answers
1k views

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 ...
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3answers
629 views

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 ...