Re: [css-images] Negative implications of linear gradient color space choice in CSS

On Sun, Jan 24, 2016 at 10:25 PM, Simon Fraser <smfr@me.com> wrote:

>
> On Jan 23, 2016, at 9:37 pm, Rik Cabanier <cabanier@gmail.com> wrote:
>
> On Sat, Jan 23, 2016 at 10:23 AM, Simon Fraser <smfr@me.com> wrote:
>
>>
>> This has been discussed several times in the past; we all agree that
>> interpolating in non-premultiplied colors
>> is better, but this is not supported by the graphics frameworks on some
>> platforms (e.g. by CoreGraphics on Mac)
>> so the spec is not able to mandate it.
>>
>
> You have it reversed. The graphics frameworks in the browsers all
> interpolate in non-premultiplied data. I had to add emulation code to all
> the browsers to make this happen.
>
>
> Are you sure?
>

Yes, I am sure. Although it looks like I forgot to add the emulation code
to Safari
If you open this in Safari:  https://jsfiddle.net/2ff05z2y/ you will see
that the gradient is not in premultiplied space.


> Gradients with a transparent endpoint in Safari look grayish near the end,
> because alpha premultiplication has caused loss most of the RGB
> information. We need to interpolate with non-premultpliied alpha to be able
> to interpolate the color components and the alpha independently.
>

Yes, they are gray-ish because the interpolate with transparent black.

Transitions should interpolate alpha and color indepently (unless you mean
straight opacity?)