Fail:Jpeg2000 2-level wavelet transform-lichtenstein.png
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Lühikirjeldus
| KirjeldusJpeg2000 2-level wavelet transform-lichtenstein.png |
The picture shows a 2 level wavelet transform. For the low-pass and high-pass filters, I have used the same of the JPEG2000, lossy transform, so that this is the wavelet that is used in the JPEG2000 format. In general, it is quite hard to show a wavelet transform properly, because of the different ranges of the different parts. I have made the following choices. First of all, I wanted to use a picture with both flat surfaces, sharp edges and details. The standard test image Lenna is commonly used for this purpose, but I didn't want to use it because it is not in the public domain. I took a look at the big featured picture gallery con Commons and I have chosen Image:Lichtenstein img processing test.png because it has lots of details in the bottom left, while the top right has almost no details because of the sky. Moreover, the edges of the castle are really sharp, so they can be clearly seen in the wavelet transform. I have saved the original image in a file called lichtenstein.png, to make it simpler. Then I have used the following Matlab script: clear all
%input must be 512x512
img=imread('lichtenstein.png');
img=im2double(img);
img=rgb2gray(img);
% filters in JPEG2000
Lo_D=[0.0267 -0.0168 -0.0782 0.2668 0.6029 0.2668 -0.0782 -0.0168 0.0267];
Hi_D=[0.0912 -0.0575 -0.5912 1.1150 -0.5912 -0.0575 0.0912];
%calculate the 2-level Wavelet transform
[scaled, vertical, horizontal, diagonal]=dwt2(img,Lo_D,Hi_D);
[scaled2, vertical2, horizontal2, diagonal2]=dwt2(scaled,Lo_D,Hi_D);
%crop pictures (for displaying purpose)
scaled2=imcrop(scaled2,[4 4 127 127]);
horizontal2=imcrop(horizontal2,[4 4 127 127]);
vertical2=imcrop(vertical2,[4 4 127 127]);
diagonal2=imcrop(diagonal2,[4 4 127 127]);
horizontal=imcrop(horizontal,[4 4 255 255]);
vertical=imcrop(vertical,[4 4 255 255]);
diagonal=imcrop(diagonal,[4 4 255 255]);
%increase contrast (for displaying purpose)
vertical=imadjust(abs(vertical));
horizontal=imadjust(abs(horizontal));
diagonal=imadjust(abs(diagonal));
vertical2=imadjust(abs(vertical2));
horizontal2=imadjust(abs(horizontal2));
diagonal2=imadjust(abs(diagonal2));
%put them all together
transform=zeros(512,512);
transform(1:128,1:128)=scaled2;
transform(1:128,129:256)=horizontal2;
transform(129:256,1:128)=vertical2;
transform(129:256,129:256)=diagonal2;
transform(1:256,257:512)=horizontal;
transform(257:512,1:256)=vertical;
transform(257:512,257:512)=diagonal;
imwrite(transform,'Jpeg2000_2-level_wavelet_transform-lichtenstein.png');
If I had placed all the transforms one next to the other, I would have got a picture wider than 512x512, with some odd behaviour close to the edges. In order to avoid those problems, I have cropped the transforms so that I can easily put one next to the other to get a 512x512 picture. In general, it is not a good idea to discard information, but here I just wanted to create a simple and clear example. In order to show the derivatives, I have taken the absolute values (I want to show the magnitude of the derivative), then I have improved the contrast to make them look clearer. |
| Kuupäev | |
| Allikas | Üleslaadija oma töö |
| Autor | Alessio Damato |
| Teised versioonid |
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Litsents
| Luba on antud selle dokumendi kopeerimiseks, avaldamiseks ja/või muutmiseks GNU Vaba Dokumentatsiooni Litsentsi versiooni 1.2 või hilisema Vaba Tarkvara Fondi avaldatud versiooni tingimuste alusel; muutumatute osadeta, esikaane tekstideta ja tagakaane tekstideta. Sellest loast on lisatud koopia leheküljel pealkirjaga "GNU Free Documentation License".http://www.gnu.org/copyleft/fdl.htmlGFDLGNU Free Documentation Licensetruetrue |
| See fail kuulub jurisdiktsiooniga sidumata Creative Commonsi litsentsi "Autorile viitamine + jagamine samadel tingimustel 3.0" alla. | ||
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| See litsentsimärgis lisati sellele failile GFDL-i litsentsimisuuenduse raames.http://creativecommons.org/licenses/by-sa/3.0/CC BY-SA 3.0Creative Commons Attribution-Share Alike 3.0truetrue |
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source of file inglise
original creation by uploader inglise
17. mai 2007
data size inglise
193 969 bait
512 piksel
512 piksel
media type inglise
image/png
checksum inglise
b150b038b08f044ba44a6178edf7922b8d9109a1
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| Kuupäev/kellaaeg | Pisipilt | Mõõtmed | Kasutaja | Kommentaar | |
|---|---|---|---|---|---|
| viimane | 6. juuli 2019, kell 09:27 | 512 × 512 (189 KB) | wikimediacommons>Alexis Jazz | Reverted to version as of 12:28, 17 May 2007 (UTC) Can't be sure if metadata, color profiles or browser compatiblity was lost. These overwrites are not needed, MediaWiki handles this. |
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