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Re: Color and RGBA [message #35504 is a reply to message #35499]

Thu, 23 February 2012 22:40

unodgs
Messages: 1366
Registered: November 2005
Location: Poland

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mirek wrote on Thu, 23 February 2012 14:52

Well, the main reason for this is that Color supports "special values" while we still want it to be 32bit entity.

OTOH, now thinking about it, it is true that Null could be represented as RGBA(0, 0, 0, 0) and RGBA(x, 0, 0, 0) could in theory represent other special values, because it is invalid in premultiplied format.

We would still need separate RGBA and Color, because RGBA is POD, but I guess things would improve. Also we might have problems with "non-premultiplied" data. Anything else I miss?

As I'm thinking about this I came to the conclusion that the most important is easy of use of the drawing API. What if Draw interface instead of Color class used RGBA structure (like in Painter). RGBA needs only a few useful constructors. According to the POD class definition ( http://www.fnal.gov/docs/working-groups/fpcltf/Pkg/ISOcxx/do c/POD.html) structure with a constructor is still a POD. Color class have operator RGBA defined so it could still be easily used with Draw.
I'm not sure if that is a perfect solution but I also know that current one is not good if it comes to transparency support.

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