Re: [compositing] Requesting clarification of color interpolation

Hi Nikos,

I shortened a bit, please see below.

On 01/21/2015 01:11 AM, Nikos Andronikos wrote:

> My understanding is that the PNG spec only says 'should'. Therefore PNG
> only recommends alpha compositing in a linear space, but this is not
> strictly required, and browsers ignore it and do all PNG composing in sRGB.
> A test: http://jsfiddle.net/dodgeyhack/ffzjtrwz/1/

Nice test! And yes it only says 'should' but it goes into great detail 
how to do so in an effort to improve the state of affairs.

>
>> I know it's really hard to find correct implementations of color
>> algorithms, but one cannot expect that to improve if something exposed
>> like W3C compositing implies it's a non-issue by silently assuming
>> sRGB compositing, even in conflict with some of SVG and PNG.
>
>> So, whatever the actual choice to go with [which is probably the
>> simple but wrong choice as the default or only option], please make it
>> explicit and well-documented, thus climbing up to 2 in the above
>> order. I volunteer to provide input if that's what is missing.
>>
>> Cheers,
>>
>> Simon
>>
> My thoughts are that the compositing spec should include a note for
> authors stating:
> - to achieve high quality/accurate colour output, all operations need to
> be performed in a linear colour space
> - the default colour space is non-linear sRGB
> - the colour space for compositing operations can be controlled with the
> color-interpolation property
>
> Then it is up to implementations to implement  color-interpolation.
> I would like to add this wording to the next version of the spec - level
> 2. I don't think it's worth revising the current CR since the advice
> cannot be acted upon currently.
>
> Would you be happy with this? And what do others think?

Indeed I would be very happy with such wording added. Allow me to 
suggest to add a reference to [1], it's an insightful and handy piece 
that is actually helpful when pondering these issues.

Cheers,

Simon

[1] J. F. Blinn, “A ghost in a snowstorm [computer graphics],” IEEE 
Computer Graphics and Applications, vol. 18, no. 1, pp. 79–84, Jan. 1998.

Received on Sunday, 25 January 2015 20:47:18 UTC