W3C home > Mailing lists > Public > whatwg@whatwg.org > February 2008

[whatwg] More random comments on the putImageData definition

From: Robert O'Callahan <robert@ocallahan.org>
Date: Mon, 11 Feb 2008 12:08:31 +1300
Message-ID: <11e306600802101508x443769c1k20427359cea41643@mail.gmail.com>
On Feb 11, 2008 11:49 AM, Ian Hickson <ian at hixie.ch> wrote:

> If we have one API, high-res only:
>
>   People who use it correctly:
>      get good results both today and tomorrow.
>   People who use it wrongly:
>      get good results today.
>      will get cropped or visibly wrong results tomorrow.
>
> If we have two APIs:
>
>   People who use it correctly:
>      get good results today.
>      may get either ugly results tomorrow, or good results tomorrow.
>   People who it wrongly:
>      get good results today.
>      get ugly results tomorrow.
>   More people will use it wrongly, since it's more complex.
>
> So we trade cropped or visibly wrong results for ugly results, and good
> results for possibly ugly results.
>

Well, "ugly" here actually means "visually just as good as today, but not as
good as the results could be on a high-DPI device".

Whereas "will get cropped or visibly wrong results tomorrow" could be so
serious that browsers simply have to lock in to "ugly mode" forever to avoid
them. Apparently I'm not the only one worried about that.

Maybe the least sucky option is to leave the API as-is, hope nothing bad
happens, and if it does then we do what Oliver suggested and make
getImageData downsample to ensure a 1:1 ratio, breaking the
getImageData/putImageData invariant but oh well. Then later when the world
is ready, introduce getImageDataReallyThisTime....

(Alternatively: if the user is a Web developer, i.e. has Firebug installed,
always make Gecko's canvas backing store 2 pixels per canvas unit! Just
kidding. I think.)

Rob
-- 
"He was pierced for our transgressions, he was crushed for our iniquities;
the punishment that brought us peace was upon him, and by his wounds we are
healed. We all, like sheep, have gone astray, each of us has turned to his
own way; and the LORD has laid on him the iniquity of us all." [Isaiah
53:5-6]
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