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Re: COMPOSITE VALUES

From: Bob Holmes <rangsynth@gmail.com>
Date: Mon, 6 Aug 2012 23:35:05 +0200
Message-ID: <CAMvo67YY=kqHAJNUWnHS+CjRovtaT5UpD-EvvHsMAh2whFgzeA@mail.gmail.com>
To: Rik Cabanier <cabanier@gmail.com>
Cc: Nikos Andronikos <Nikos.Andronikos@cisra.canon.com.au>
Thanks. I get that now. I first learned from places like Skia and Agg 2.4
source where the alpha is included in the MULTIPLY for example, so I have
been reading all these different versions and implementations. It was hard
for me to see this actually but it is definitely much better with the split
blend and composite and the blender only doing RGB.

On Mon, Aug 6, 2012 at 11:08 PM, Rik Cabanier <cabanier@gmail.com> wrote:

> alpha of the source is unaffected by the blending.
>
>
> On Mon, Aug 6, 2012 at 10:17 AM, Bob Holmes <rangsynth@gmail.com> wrote:
>
>> In case it still was not 100% clear...
>>
>> This is composite for DSTOVER IN NEW SPEC
>>
>> co = s x Cs x (1 - b) + b x Cb
>> o = s x (1 - b) + b
>>
>> Specifically where does "s" come from. Does it come from "Cs" as is
>> after the blending or before the blending? Because the result of the
>> blending is Cs and so is the input color to the blending etc...
>>
>> On 8/6/12, Bob Holmes <rangsynth@gmail.com> wrote:
>> > For example...
>> >
>> > XOR...
>> >
>> >     co = s x Cs x (1 - b) + b x Cb x (1 - s)
>> >
>> > Is "as" the alpha of the input source or the alpha of Cs after
>> > blending function.
>> >
>> > If the blending function is implemented to return premultiplied value
>> > the formula can then be...
>> >
>> >     co = cs x (1 - b) + cb x (1 - s)
>> >
>> > ?
>> >
>>
>
>
Received on Monday, 6 August 2012 21:35:34 GMT

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