LCE: Don't play dice with random numbers
Posted Nov 25, 2012 6:10 UTC (Sun) by rgmoore
In reply to: LCE: Don't play dice with random numbers
Parent article: LCE: Don't play dice with random numbers
That's a good idea, but some of the implementation details are wrong in a way that might cause real world problems. For one thing, digital cameras sensors* measure the value for only one color at each physical pixel location. The three color final picture is the result of a complex color interpolation routine, which should result in correlation between the values in adjacent pixels. So in practice, you'll want to get the raw, uninterpolated sensor data rather than the final three colors per pixel interpolated data. Also, many real-world sensors have some kind of correlation between nearby pixels that isn't the result of the interpolation routines; it shows up as "pattern noise" in low-light pictures and is a major limit on many cameras' ability to take pictures in low light.
And as long as you're looking only at the least significant digits at each pixel, you shouldn't actually need to cover the lens. The least significant value is subject to shot noise as long as the pixel isn't anywhere close to saturation. Testing to make sure that it isn't saturated should be pretty easy, so you could probably get some useful randomness by appropriate use of a webcam without needing any modification.
*With the exception of those using Foveon's x3 technology, which is limited to a few expensive models you probably aren't going to be using for these applications.
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