HTML foreground and background colors being the same... poll time!

["William M. Perry" <wmperry@aventail.com>]

Ok, so what should Emacs/W3 do if someone happens to lose so badly as to
specify a background or foreground color without also specifying the other?

We could:

a) Do nothing (current practice)
b) Infer the missing color by taking rgb(~r,~g,~b) 
c) Infer the color some other way?

a is ugly and bad and should change, I think we would all agree.

b is pretty easy to implement:

(defun infer-contrasting-color (r g b)
  (if (and (<= r 255)
	   (<= g 255)
	   (<= b 255))
      (format "#%02x%02x%02x"
	      (logxor r 255)
	      (logxor g 255)
	      (logxor b 255)))
  (format "#%04x%04x%04x"
	  (logxor r 65535)
	  (logxor g 65535)
	  (logxor b 65535)))


but for things like a pure red background it ends up giving you aquamarine, 
which is kind of eye searing.

I'd vote for (c), but I have no clue on how to go about finding or writing
a good contrast-finding algorithm.  Anyone out there know of one?

-Bill P.