Re: [matplotlib-devel] color mix

[Paul K. <pki...@em...>]

On Sep 23, 2008, at 8:29 PM, Tom Holroyd wrote:

> Repost; the list bounced my last attempt.
>
> On Fri, 2008-09-19 at 18:42 -0400, Tom Holroyd wrote:
>> On Thu, 2008-09-18 at 20:40 +0200, Jouni K. Seppänen wrote:
>>> I would prefer something like the following options:
>>>
>>>     fc={'orange': 20, 'white': None}
>>>     fc=[[20, 'orange'], [None, 'white']]
>>>     fc=ColorMixture('orange', 20, 'white') # where ColorMixture  
>>> is a fairly
>>>                                            # trivial class
>>
>> +1
>>
>> simpler, easier to read & write, less ad-hoc
>>
>> I'd go ahead and make ColorMixture a fancy class with __rmul__ and
>> __add__ methods to allow things like
>> 	orange = ColorMixture(255, 165, 0)
>> 	blue = ColorMixture(0, 0, 255)
>> 	mycolor = .7 * orange + .2 * blue

hsv mixing is much more useful.  Take a known color and you can imagine
what a darker/lighter or paler/deeper version would look like, such as
dark green or pale blue.  These are just value and saturation.  Even hue
can be imagined to some degree (bluish, greenish, etc.) to move one hue
toward another, but that is harder to imagine across the circle
(e.g, greenish purple or bluish yellow).

Rather than averaging it would be easier to move some percentage toward
the other color, such as blue, but hue 20% toward green.

This can probably be expressed in operations on a color mixture class
as above.

Also a linear perceptual scale would work better than HSV but I don't
know of one off hand.

- Paul