9 ms·
It's really neat that you can through away 50% of the high frequencies and the picture will still look good enough for normal everyday use
by jarenmf 6y ago
It's really neat that you can through away 50% of the high frequencies and the picture will still look good enough for normal everyday use
- 2rsf 6y agoA lot of media (audio, video) compression methods are based on that though they usually use more sophisticated filtering methods.
- nchelluri 6y agoI think JPEG is too. In school, we implemented something like JPEG compression using some Fourier transform stuff that reduced the bitmap size by 90%+ and was still fairly decent looking. It was an image handpicked for suitability under compression, I'm sure. A sunflower, I think?
- mdiesel 6y agoAh, you were too young to use the correct image for all testing purposes: Lena Forsén.
- echelon 6y agoThe image processing community has moved away from Lena. It's a sexist nude crop from Playboy Magazine. It's uncomfortable and gross to use that in a professional setting where we're meant to be welcoming and inclusive. https://pursuit.unimelb.edu.au/articles/it-s-time-to-retire-lena-from-computer-science https://pursuit.unimelb.edu.au/articles/it-s-time-to-retire-...
- mdiesel 6y agoYou're right, and I'd never considered it before. Thanks for the link.
- nyanpasu64 6y agoI had a similar kind of lab in college. I ended up testing it on an image hand-picked for performing very poorly under JPEG compression, a GBA Pokemon game screenshot. Chroma subsampling alone visibly degraded the sharpness of brightly colored objects. Strangely chroma subsampling degrades photographic imagery far less, and helps less sophisticated algorithms (like JPEG) allocate limited bits better.
- rademacher 6y agoThey use wavelet transforms for jpeg 2000. Natural images tend to be sparse with respect to wavelet transforms.
- qppo 6y agoYou get even better results using a DCT instead of DFT since the bins are less correlated.