[Haskell-cafe] ANN: AC-Vector, AC-Colour and AC-EasyRaster-GTK

Max Rabkin max.rabkin at gmail.com
Sat Jul 4 15:35:52 EDT 2009

On Sat, Jul 4, 2009 at 9:18 PM, Andrew
Coppin<andrewcoppin at btinternet.com> wrote:
>>> 2. It's mind-blowingly complex.
>> Colour *is* complex. Which is why I'm so glad Russell O'Connor did all
>> the hard work for me :)
> Well, no, because now I'm going to have to spend a few hours trying to find
> out what CIE is before I can even use that library.

The sRGB function makes a Colour from RGB (actually sRGB, which is a
"standardised" RGB -- basically RGB where the exact frequency and
power of each channel is specified -- but you can pretend your
monitor's RGB is sRGB.

> So mappend gives you colour addition [with the perplexing comments about
> "gamut", presumably some kind of small mammal?]

The gamut of a device is the range of representable colours (a
monitor's gamut looks something like a parabola with a flat base in
XYZ space, whereas a printer's is much more complex and variable).
This makes sense. If you double a monitor's brightest white, you don't
get a colour twice as bright: you get the same colour.

> but there's no subtraction?
> No multiplication? No linear blending?

affineCombo can do subtraction, again with the gamut warning. darken
does scalar multiplication; it probably doesn't do componentwise
multiplication, which doesn't make much sense if you're trying to work
in a coordinate-independent setting, though I admit RGB-multiplication
can be handy.

> Heh, my colour library includes a custom floor implementation that talks to
> the GHC primops directly because calling floor is too slow...
> [In case that sounds like idle talk, I had a program go from 10 seconds to
> less than 1 second just by using this function. There's a few tickets about
> it on the GHC Trac.]

Fair enough. Can your implementation not be turned into a patch?

BTW, I'm also working on Haskell fractals. You might be interested in
looking at my fractal package (though it's currently undocumented, and
has no GUI).


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