File:Antialiased-sinc.png
Antialiased-sinc.png (128 × 128 pixels, file size: 13 KB, MIME type: image/png)
Captions
sinc filter antialiased chessboard
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If the current image is the same as when I (Loisel 23:40 14 Jul 2003 (UTC)) wrote this comment, the following Matlab code was used to generate the image:
function Z=filteredchessboard(n,a); foo=(1:n)*128.0/n; m=size(foo,2); disp('Initializing X, Y') for i=1:m X(:,i)=(foo-64.0)'; Y(i,:)=foo; end disp('Generating unfiltered chessboard') T=1.0./(Y/2048.0+0.001); Z=T.*(X/128.0); I0=floor(T); J0=floor(Z); K=I0+J0; C=mod(K,2); disp('Calculating Fhat') Fhat=fft2(C); f1=floor(m/a); f2=n-f1; f1=f1+1; f2=f2+1; disp('Zeroing middle frequencies') Fhat(f1:f2,:)=0; Fhat(:,f1:f2)=0; disp('Inverse Fourier transform & output') Z=real(ifft2(Fhat));
The returned matrix (e.g. from filteredchessboard(1024,20)) can be viewed with, eg,
image(10*Z')
I then clamped the image like so:
X=max(min(1,Z),0);
in Matlab. Then I took a submatrix of size 128 (e.g., X(1:10:(10*128),1:10:(10*128))) and I wrote it to a file using dlmwrite. Then I wrote a short C program to extract the floating point numbers and convert them into a .pgm file. Lastly, using Gimp, I converted the image to rotate the image 90 degrees and save it to png.
date/time | username | edit summary |
---|---|---|
19:21, 22 December 2004 | en:User:Quadell | (tagged) |
00:21, 15 July 2003 | en:User:Loisel | (updated comments for updated image) |
23:40, 14 July 2003 | en:User:Loisel | (signed) |
23:39, 14 July 2003 | en:User:Loisel | (<tt> -> <pre>) |
23:22, 14 July 2003 | en:User:Loisel | (howto reproduce image) |
23:18, 14 July 2003 | en:User:Loisel | (<a href="/wiki/Sinc_filter" title="Sinc filter">sinc filter</a> antialiased chessboard) |
Original upload log
[edit]Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version.
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- (del) (cur) 13:34, 30 September 2005 . . en:User:Riumplus Riumplus ( en:User_talk:Riumplus Talk) . . 128x128 (12995 bytes) (Losslessly recompressed the image, shrinking file size by 2%)
- (del) (rev) 01:01, 15 July 2003 . . en:User:Loisel Loisel ( en:User_talk:Loisel Talk) . . 128x128 (13271 bytes) (bugfix)
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Date/Time | Thumbnail | Dimensions | User | Comment | |
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current | 16:53, 18 March 2006 | 128 × 128 (13 KB) | Maksim (talk | contribs) | La bildo estas kopiita de wikipedia:en. La originala priskribo estas: sinc filter antialiased chessboard {{GFDL}} If the current image is the same as when I (Loisel 23:40 14 Jul 2003 (UTC)) wrote this comment, the following Matlab co |
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