lecture04: Sampling and transforms in 2D
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http://en.wikipedia.org/wiki/Dithering
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http://en.wikipedia.org/wiki/Web_colors
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http://www.is.kiruna.se/~cjo/d2i/COLOR.RGB.html
http://www.kenjikojima.com/java/RGBHexConverter2.html
http://en.wikipedia.org/wiki/Discrete_cosine_transform
http://www.cs.sfu.ca/CourseCentral/365/li/interactive-jpeg/Ijpeg.html
http://www.jjtc.com/stegdoc/steg1995.html