On Nov 11, 2012, at 9:06 PM, Rik Cabanier <caban...@gmail.com> wrote:
> > > On Sun, Nov 11, 2012 at 8:43 PM, Maciej Stachowiak <m...@apple.com> wrote: > > On Nov 11, 2012, at 6:59 PM, Rik Cabanier <caban...@gmail.com> wrote: > >> >> >> >> Wouldn't it be better to add a new property to canvas for blending? At the >> beginning, implementations are just require to use different blend modes in >> combination with 'source-over'. >> >> That could work too. >> There was a mailing list conversation about this a couple of months ago, and >> people were evenly split on the subject. >> >> The vast majority of cases will use 'source-over' in combination with >> blending so maybe it's best to keep it simple... > > It doesn't make sense to me for blend mode and composite operator to be > separate in CSS, but combined in Canvas. Either there are valid use cases for > specifying them separately or there are not. I cannot imagine how this could > differ between Canvas and CSS. > > There are cases where it makes sense to have them as separate properties. > To be honest, the main reason that the Canvas proposal combines them, is > because it is not possible to implement this efficiently using Core Graphics. > > If we break it up in 2 operations, we have to document the correct behavior > (= blending does not force source-over for blending) because the spec can't > be changed later. > This means that Safari and Firefox for Mac can only implement part of the > spec... > > I prefer to have a consistent implementation that can be extended later as > opposed to a 'correct' API that is inconsistently implemented. Doesn't this same argument apply to CSS blend modes? (And therefore the 'blend-mode' and 'alpha-compositing' properties should be combined into a single property)? Regards, Maciej
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