[webkit-dev] Adding blending mode to WebKit canvas

[Rik Cabanier]

On Mon, Nov 12, 2012 at 12:07 PM, Ilyes Gouta <ilyes.gouta at gmail.com> wrote:

> Hi,
>
> On Nov 12, 2012 4:39 PM, "Dirk Schulze" <dschulze at adobe.com> wrote:
> >
> >
> > On Nov 11, 2012, at 10:09 PM, "Rik Cabanier" <cabanier at gmail.com> wrote:
> >
> >>
> >>
> >> On Sun, Nov 11, 2012 at 9:52 PM, Dirk Schulze <krit at webkit.org> wrote:
> >>>
> >>>
> >>>
> >>> On Sunday, November 11, 2012, Rik Cabanier wrote:
> >>>>
> >>>>
> >>>>
> >>>> On Sun, Nov 11, 2012 at 8:43 PM, Maciej Stachowiak <mjs at apple.com>
> wrote:
> >>>>>
> >>>>>
> >>>>> On Nov 11, 2012, at 6:59 PM, Rik Cabanier <cabanier at 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.
> >>>
> >>>
> >>> To be fair, the 'globalCompositOperator' property mixed the
> compositing modes with some blend modes already. Which is the fault of the
> WebKit implementation. IIRC they have been removed from the Canvas part of
> the HTML spec for some time, but were added later again. Now we have
> multiple independent implementations that support all currently specified
> operators.
> >>
> >>
> >> Is this the 'darker' compositing mode or are there others?
> >
> >
> > Lighter and darker, yes.
>
> Is additive blending also specified/supported?
>
They are not.
I proposed adding all the photoshop blend modes to the spec but got
pushback.

They are also not part of Core Graphics so it would be hard to implement
them.
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