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

Jpeg2000_2-level_wavelet_transform-lichtenstein.png(512 × 512 piksèl, gwosè fichye a : 189 kio, tip MIME li ye : image/png)

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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.
Dat
Sous Travay pèsonèl
Kreyatè Alessio Damato
Autres versions
The original picture

Kondisyon itlizasyon

Moi, en tant que détenteur des droits d’auteur sur cette œuvre, je la publie sous les licences suivantes :
GNU head Ou bay pèmisyon pou kopye, distribye ak/oswa modifye dokiman sa a dapre kondisyon GNU Free Documentation License, Vèsyon. 1.2 oswa nenpòt vèsyon ki pibliye pita pa Free Software Foundation; san okenn Seksyon ki pa ka chanje, pa gen okenn Tèks ak premye paj kouvèti, epi pa gen okenn Tèks Denyè-Kouvèti. Gen yon kopi lisans lan nan seksyon ki rele GNU Free Documentation License.
w:fr:Creative Commons
Rekonèt avèk non otè Enfòmasyon sa yo ka pataje
Fichye sa a distribiye selon lisans Creative Commons.
Ou gen dwa:
  • pou pataje – pou kopye, distribiye epi difize ouvraj la
  • pou remiks – pou adapte ouvraj la
Selon kondisyon sa a yo:
  • Rekonèt avèk non otè – Ou dwe bay enfòmasyon apwopriye sou otè a, bay yon lyen pou lisans lan, epi endike si te gen chanjman ki fèt. Ou ka fè sa nan nenpòt fason rezonab, men okenn fason ki sijere ke otè a soutni oswa apwouve itilizasyon ou an.
  • Enfòmasyon sa yo ka pataje – Si ou fè rekopye, transfòme, oswa baze sou materyèl sa, ou dwe distribye kontribisyon ou anba menm oswa yon lisans konpatib avèk orijinal la.
Ce bandeau de licence a été ajouté à ce fichier dans le cadre de la procédure de mise à jour des licences des images sous GFDL.
w:fr:Creative Commons
Rekonèt avèk non otè Enfòmasyon sa yo ka pataje
Ce fichier est sous licence Creative Commons Attribution – Partage dans les Mêmes Conditions 2.5 Générique, 2.0 Générique et 1.0 Générique.
Ou gen dwa:
  • pou pataje – pou kopye, distribiye epi difize ouvraj la
  • pou remiks – pou adapte ouvraj la
Selon kondisyon sa a yo:
  • Rekonèt avèk non otè – Ou dwe bay enfòmasyon apwopriye sou otè a, bay yon lyen pou lisans lan, epi endike si te gen chanjman ki fèt. Ou ka fè sa nan nenpòt fason rezonab, men okenn fason ki sijere ke otè a soutni oswa apwouve itilizasyon ou an.
  • Enfòmasyon sa yo ka pataje – Si ou fè rekopye, transfòme, oswa baze sou materyèl sa, ou dwe distribye kontribisyon ou anba menm oswa yon lisans konpatib avèk orijinal la.
Chwazi lisans ou vle a.

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Kounye a6 jiyè 2019 à 08:27Minyati pou vèsyon 6 jiyè 2019 à 08:27512 × 512 (189 kio)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.
5 jiyè 2019 à 23:28Minyati pou vèsyon 5 jiyè 2019 à 23:28512 × 512 (183 kio)C 1File size reduced by 7KB using OptiPNG, a lossless optimizer/recompressor for PNG images. No changes made to image or metadata.
17 me 2007 à 12:28Minyati pou vèsyon 17 me 2007 à 12:28512 × 512 (189 kio)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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