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Questions tagged [dwt]

DWT stands for Discrete Wavelet Transform. This transformation is commonly used in signal processing. Its main advantage over Fourier transform is its ability to preserve temporal information.

DWT stands for Discrete Wavelet Transform. This transformation is commonly used in signal processing.
Wavelets are considered as more advanced tool than Fourier transform for signal processing. DWT's main advantage is its ability to preserve temporal information of the signal while introducing frequency properties. This advantage is achieved due to the use of compact basis functions - the wavelets. The compact basis functions integrates spectral (frequency) information over compact domain thus preserving temporal information.

There are many types of DWT differes by their construction of their basis function. Very useful DWTs are Haar wavelets and Gabor wavelets.

For more information see wikipedia.

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Image super resolution algorithm in Matlab

I'm trying to implement a simple Image super resolution algorithm (DWT-Based Resolution Enhancement ) in the following paper http://www.ripublication.com/aeee/52_pp%20%20%20405-412.pdf I tried to implement the algorithm in figure 3 of this paper…
Celine
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Implementing Discrete Wavelet Transformation in C

I am trying to implement DWT on gray images in C++. I saw an OpenCV implementation at https://stackoverflow.com/a/20072775/3024435. The article at http://www.whydomath.org/node/wavlets/hwt.html was useful in understanding and implementing low/high…
user3024435
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Issue in accessing package variable in Dreamweaver Template

I am facing a issue in accessing a package variable in DWT of Page Template. I have a compound page template with 4 TBB's as follows: 1) Constant TBB - This TBB reads all values of a component(Embedded multivalued component) as key-value pairs and…
Vinda Sawant
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Matlab dwt across specified dimension

I have a dataset Sig of size 65536 x 192 in Matlab. If I want to take the one-dimensional fft along the second dimension, I could either do a for loop: %pre-allocate ect.. for i=1:65536 F(i,:) = fft(Sig(i,:)); end or I could specify the…
Ghaul
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How do I find local threshold for coefficients in image compression using DWT in MATLAB

I'm trying to write an image compression script in MATLAB using multilayer 3D DWT(color image). along the way, I want to apply thresholding on coefficient matrices, both global and local thresholds. I like to use the formula below to calculate my…
Nitwit
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Wavelet from scratch, but how to inverse it in python

I have the data and code below that creates a DWT wavelet, but I don't know how to inverse it so that it aligns with the original data. The code below works to create the coefficients but then I'm stuck on inversing it. I don't want to use a package…
tone
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Discrete Wavelet Transform (DWT) and Stationary Wavelet Transform (SWT) in Java

I want to apply DWT and SWT to images in Java but can't find code, pseudocode or libraries for that. Until now, I only found existing code in other languages like C, C++ or Python but I need it in Java and I'm not able to change the code from one to…
javagirl96
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Divide an image into non-overlapping blocks and applying the 2D DWT on each block

I am working on creating an image splicing detection software so I need to divide the image into non-overlapping blocsk and apply Discrete Meyer Wavelet Transform on each block of the image I have tried the blockproc function to do that but I got…
Mohammed Kassem
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Discrete wavelet transformation on image using 'haar' wavelet in python

I am trying to apply haar wavelet on an image in python. Here is the code from pywt import dwt2, idwt2 img = cv2.imread('xyz.png') cA, (cH, cV, cD) = dwt2(img, 'haar') Then I modify coefficients embedding some data like given…
Shaan
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how to display multi-level wavedec2 in MATLAB

After computing the 4-level discrete wavelet transform of an image, how do I display this multi-level transformation in matlab? And how do I plot the histogram of the corresponding DWT coefficients? Here is what I did so far: I =…
ABC2013
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Input to the Haar Wavelet Transform is not power of 2

If the input data is not even, what should I do? And what if the input data is not power of 2? Should I just ignore the rest of the numbers?
Yuhang Lin
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How can I apply cropping attack for watermarking?

When I apply crop attack on watermarked image it gives me a corrupted extracted watermark. Extracted watermark shows black at bottom of the corner but, it should not be black. How can I solve this problem? How can I apply crop attack? Watermarked…
M.Dogru
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Calculating Energy of image frame using DWT in python shows wrong value

I want to find the energy of the image frame. This is how I calculated in Matlab. [~,LH,HL,HH] = dwt2(rgb2gray(maskedImage),'db1'); % applying dwt E = HL.^2 + LH.^2 + HH.^2; % Calculating the energy of each pixel. Eframe = sum(sum(E))/(m*n); %…
user2408205
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Haar wavelets - Partial signal reconstruction

I'm trying to approximate a time series/vector usind dwt. I can apply the full dwt and idwt reconstruction, but i don´t know how to reconstruct/approximate the original signal based on just a few coefficients (not all). I tryed…
Nelson
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How can I reduce the execution time required by SPECK, SPIHT and EZW?

I am compressing images using DWT and DWT based entropy coders like SPECK, SPIHT and EZW using MATLAB. However, the execution time required by these entropy coders is too high. Is there any solution to this?
S. Kahu
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