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Re: [whatwg] Enabling LCD Text and antialiasing in canvas

From: Stephen White <senorblanco@chromium.org>
Date: Fri, 19 Apr 2013 13:35:26 -0400
Message-ID: <CAPeKFTjtz-M9r3m+aJCS3EOQKrxZ29_r7bgu=mQ3p8HA1ANBCw@mail.gmail.com>
To: Rik Cabanier <cabanier@gmail.com>
Cc: Gregg Tavares <gman@google.com>, WHATWG <whatwg@lists.whatwg.org>, James Robinson <jamesr@google.com>, Mark Callow <callow.mark@artspark.co.jp>, Robert O'Callahan <robert@ocallahan.org>
Thanks for your comments.

On Fri, Apr 19, 2013 at 12:53 PM, Rik Cabanier <cabanier@gmail.com> wrote:

> Nice!
>
> The behaviour of putImageData() and putImageDataHD() is to premultiply the
> RGB components by the alpha component as usual, but write 1.0 into
> destination alpha. In other words, if (r, g, b, a) are the component values
> in a given pixel passed to putImageData[HD](), then r' = ar, g' = ag, b' =
> ab are the colour components of the resulting canvas pixel, and (r', g',
> b', 1.0) is written to the canvas backing store.
>
> I think that's confusing. Maybe cut that sentence since it isn't needed.
> (Having the black backing store implies this behavior)
>

Do you mean, remove both sentences, or just the last one?  I wanted to make
it clear that the RGB is still premultiplied with the original alpha, even
though the alpha is subsequently ignored.

attribute boolean alpha;
>
> Should it be read-only?


Hmm, I have no idea.  WebGL's doesn't have it, but I'm not enough of an IDL
expert to know whether it's necessary.


>
> Canvas2DContextAttributes getContextAttributes();
>
> Maybe make it an attribute:
>
> attribute Canvas2DContextAttributes attributes:
>
>
I'm following WebGL syntax here as well.  Apparently WebGL's is nullable,
though, so I've added ? here.

Stephen

>
> On Fri, Apr 19, 2013 at 9:13 AM, Stephen White <senorblanco@chromium.org>wrote:
>
>> Here's a short proposal I've written up for the getContext('2d', { alpha:
>> false } ) version of this idea (much of it culled from the mega-thread
>> above).
>>
>> http://wiki.whatwg.org/wiki/CanvasOpaque
>>
>> Comments are welcome.
>>
>> Stephen
>>
>
>
Received on Friday, 19 April 2013 17:35:55 UTC

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