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Interesting. But if I understand correctly, this will not retain images sharpness? It's not easy to see with just a 2x increase.
by kken 13y ago
Interesting. But if I understand correctly, this will not retain images sharpness? It's not easy to see with just a 2x increase.
- eliteraspberrie 13y agoYes, the sharpness does decrease with the interpolation. I think the phenomenon is called "overshoot" and I don't know how to mitigate that. Here is the image interpolated 4X: http://imgur.com/a/8YrxG http://imgur.com/a/8YrxG
- kken 13y agoIt's actually called "ringing" and can easily be explained by the fact that you convolved with a box-function in the frequency space (ideal low pass), which will transform into a sinc function in the local space. http://www.thefouriertransform.com/pairs/box.php http://www.thefouriertransform.com/pairs/box.php
- fat0wl 13y agoYou can actually see it if you look closely -- there is a kind of striping of light/dark horizontal lines, easy to spot at the top & bottom of the image.
- eliteraspberrie 13y agoThanks. I'll add a window function and see if that helps.
- oakwhiz 13y agoI'm surprised that the ringing isn't that bad even without a window function.
- angersock 13y agoTry it with a checkerboard pattern--somewhat the pathological case. Gray cats are somewhat smooth from a signal standpoint.
- eliteraspberrie 13y agoGood idea. Here's the result: http://imgur.com/a/EHNH0 http://imgur.com/a/EHNH0 Edit: I'll be adding a window function soon to attenuate the ringing, it'll be interesting to see the difference that makes.
- dnautics 13y agoyou can also try to apply a smoothening function: Usually multiplying by a gaussian in phase space will do, but this will cause your image to be blurred. What would be really impressive is if you could interpolate a pattern in the high frequency signal, and use it to "infer" values for your high frequency padding that "naturally cancel out" ringing to below the resolution of the imag.e
- angersock 13y agoA beautiful example of ringing. :)
- wfunction 13y agoI think you've convoluted the terminology. It's "convolve".
- kken 13y agowhat? :)
- dnautics 13y agoalso known as the gibbs phenomenon.
- deleted 13y ago[deleted]