What's a good interface for sRGB colours?

Question

I'm writing a ray-tracer, which uses Python to define its scene files.  The ray-tracer itself handles sRGB gamma correctly, but I'm having a hard time coming up with an interface that exposes that functionality clearly to the user.  I'll explain with an example:
Intuitively, one would expect Color(1, 1, 1)/2 to equal Color(0.5, 0.5, 0.5).  But because of sRGB gamma, that's not a half-intensity white.  So two lights with Color(1, 1, 1)/2 would not look the same as one full-brightness light, which would be confusing.
My current idea is to have two different types for colours: "Color" for colours in the linear space, and "sRGB" for colours in the sRGB space.  Is there a better way, that would hide more of the complexity of sRGB gamma from users?

Answer 1

I couldn't get the link to work to examine the code, so I'm just working off of assumptions.
If the Color object stores channel information in a list, iterators might be a natural fit:
color_1 = Color(1, 1, 1)
# one-liner using list comprehensions and parameter expansion
color_2 = Color(*[channel / 2 for channel in color_1.channels])
# slightly more verbose using an extra variable
channels = [channel / 2 for channel in color_1.channels]
color_3 = Color(*channels)
# using a for loop
channels = []
for channel in color_1.channels:
channels.append(channel)
color_4 = Color(*channels)
You might also try having a of_ratio (forgive unintuitive naming class method (alternate constructor) in your Color class:
# This code is untested, but the general idea should hopefully be obvious enough
class Color
def __init__(self, r, g, b):
self.r = r
self.g = g
self.b = b
@classmethod
def of_ratio(cls, ratio):
return Color(*[channel * ratio for channel in cls.channels])
@property
def channels(self):
return [self.r, self.g, self.b]
# example usage
color_1 = Color(1, 1, 1)
color_2 = Color.of_ratiof(color_1, 0.5)
edit:
I just remembered, you could do operator overloading.
Just implement __add__ __sub__ __div__ __mul__, etc respectively.
Last edited by aspidites (2011-12-04 05:59:26)