color library

[Kagamin via Digitalmars-d]

On Monday, 22 June 2015 at 08:45:38 UTC, Andrea Fontana wrote:
> They used to pack alpha informations with other pixel infos 
> (color) just for simplicity and to have a convenient way to 
> store info inside a file, I guess.

Separate mask has an advantage of lower memory consumption: it 
can have 1-bit depth. It was important in 90s when you didn't 
have lots of RAM and HDD and didn't need transparency deeper than 
1 bit, masks were used to only outline a crop region, which 
worked with RLE compression well further decreasing mask size, so 
it made no sense to waste space on 8-bit alpha channel.