[Pharo-dev] Why Color rgb components are on 10 bits?

Nicolas Cellier nicolas.cellier.aka.nice at gmail.com
Thu Dec 19 12:06:36 EST 2013

I know the answer, we have 30 bits available for keeping the rgb instance
variable as SmallInteger...
So it's the best we can do, while keeping an efficient format.

But we are never using 10 bits for each component, for 32 bits image only 8
bit by color are used.
Since nowadays most Forms are 32 bits deep, this force useless conversions
where we could have none.

I see that Pharo 3.0 did unify Color and TranslucentColor by moving the
alpha information in Color.
But did not change the rgb ComponentMax... Any reason why?

If we encoded rgb component on 8 bits, and reverted the alpha channel
encoding, then we could have colors pre-encoded on 32 bits, but most using
only 24 bits (because most are opaque) would be represented as SmallInteger.
But I don't know if it is really inter-operable, or more natural...

Juan followed another path for Cuis, opting for float components, which is
another possibility, but our VM are not yet optimized for handling Floats...

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