File:160 by 160 thumbnail of 'Green Sea Shell' - 1.1. fourier filtered image for downsampling to 40 x 40 in fourier domain.png
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English: 160_by_160_thumbnail_of_'Green_Sea_Shell' - 1.1. fourier filtered image for downsampling to 40 x 40 in fourier domain.
In R channel in fourierdomain, logarithmic. Zero frequency in the center. matlab Code: filt=zeros(160,160); filt(1:20,1:20)=1; filt(end-19:end,1:20)=1; filt(1:20,end-19:end)=1; filt(end-19:end,end-19:end)=1; x160_f(:,:,1)=ifft2(fft2(double(x160(:,:,1))).*filt); x160_f(:,:,2)=ifft2(fft2(double(x160(:,:,2))).*filt); x160_f(:,:,3)=ifft2(fft2(double(x160(:,:,3))).*filt); figure; imagesc(fftshift(log(abs(fft2(x160_f(:,:,1)))))); % information content of the R channel sum(sum(abs(fft2(x160_f(:,:,1)))))./sum(sum(abs(fft2(x160(:,:,1))))) % 32.99% of the relevant effective infromation is retained instead of the expected 6.25% (1/16) -> 5.28x more information as expected, ultimately due to the low frequency character and fourier domain sparsity of the image |
| Date | |
| Source | File:160_by_160_thumbnail_of_'Green_Sea_Shell'.png |
| Author | James Petts / shaddim |
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| Date/Time | Thumbnail | Dimensions | User | Comment | |
|---|---|---|---|---|---|
| current | 21:21, 5 April 2017 | | 1,116 × 876 (24 KB) | Ayane m | 44% file size reduction |
| 11:33, 3 April 2016 |  | 1,116 × 876 (43 KB) | Shaddim | User created page with UploadWizard |
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