Датотека:Jpeg2000 2-level wavelet transform-lichtenstein.png

Jpeg2000_2-level_wavelet_transform-lichtenstein.png(512 × 512 piksela, veličina datoteke: 189 kB, MIME tip: image/png)

Opis izmene

Opis

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.
Datum
Izvor Sopstveno delo
Autor Alessio Damato
Ostale verzije
The original picture

Licenciranje

Ja, nosilac autorskih prava nad ovim delom, objavljujem isto pod sledećim licencama:
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w:sr:Krijejtiv komons
autorstvo deliti pod istim uslovima
Ova datoteka je dostupna pod licencom Creative Commons Autorstvo-Deliti pod istim uslovima 2.5 Generička licenca, 2.0 Generička licenca i 1.0 Generička licenca.
Dozvoljeno je:
  • da delite – da umnožavate, raspodeljujete i prenosite delo
  • da prerađujete – da preradite delo
Pod sledećim uslovima:
  • autorstvo – Morate da date odgovarajuće zasluge, obezbedite vezu ka licenci i naznačite da li su izmene napravljene. Možete to uraditi na bilo koji razuman manir, ali ne na način koji predlaže da licencator odobrava vas ili vaše korišćenje.
  • deliti pod istim uslovima – Ako izmenite, preobrazite ili dogradite ovaj materijal, morate podeliti svoje doprinose pod istom ili kompatibilnom licencom kao original.
Izaberite licencu po želji.

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Vikimedija Serbian (transliteracija): Alejo2083
skraćeno ime autora Serbian (transliteracija): Alessio Damato

status autorskog prava Serbian (transliteracija)

zaštićeno autorskim pravima Serbian (transliteracija)

izvor datoteke Serbian (transliteracija)

sopstveno delo Serbian (transliteracija)

17. maj 2007

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Datum/vremeMinijaturaDimenzijeKorisnikKomentar
trenutna10:27, 6. jul 2019.Minijatura za verziju na dan 10:27, 6. jul 2019.512 × 512 (189 kB)Alexis JazzReverted 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.
01:28, 6. jul 2019.Minijatura za verziju na dan 01:28, 6. jul 2019.512 × 512 (183 kB)C 1File size reduced by 7KB using OptiPNG, a lossless optimizer/recompressor for PNG images. No changes made to image or metadata.
14:28, 17. maj 2007.Minijatura za verziju na dan 14:28, 17. maj 2007.512 × 512 (189 kB)Alejo2083{{Information |Description= 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 qu

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