Re: [CSS Images] syntax for color interpolation hint

On Fri, Oct 3, 2014 at 8:31 PM, Robert O'Callahan <robert@ocallahan.org>
wrote:

> On Fri, Oct 3, 2014 at 12:22 PM, Rik Cabanier <cabanier@gmail.com> wrote:
>
>> On Thu, Oct 2, 2014 at 9:06 PM, Robert O'Callahan <robert@ocallahan.org>
>> wrote:
>>
>>> I'm unconvinced this syntax is a good idea. Using a fake color stop for
>>> this purpose just seems like a hack.
>>>
>>
>> Why is this a hack? It matches how authoring tools present midpoints in
>> their UI's: they are shown as color stops with no color
>>
>
> Do you mean "some Adobe authoring tool" or a broad range of authoring
> tools?
>

A broad range, for instance:
Cinema 4D: http://www.samwirch.com/files/sky-material-gradient.png
CorelDraw:
http://community.coreldraw.com/cfs-filesystemfile.ashx/__key/CommunityServer.Components.PostAttachments/00.00.10.59.47/gradient-fill.GIF
Microsoft expression design:
http://i.msdn.microsoft.com/cc265059.newsletter_09_01_LoCascio(en-us,MSDN.10).png
Bryce:
http://www.robinwood.com/Catalog/Technical/BryceTuts/BryceClasses/BBryce5/Lesson5Graphics/05-20MoveTransition.jpg


>
>>
>>> If someone accidentally leaves out a color from a color stop they will
>>> trigger this feature accidentally. It also means there are edge cases we
>>> have to check for and reject in the parser, e.g. consecutive fake color
>>> stops. It's also not particularly extensible; we're consuming this part of
>>> the syntax (color-less stop) for a particular feature that isn't directly
>>> related to that syntax.
>>>
>>
>> Why do you think it's not extensible? If we want to support more
>> midpoints later, we can certainly add support for that by being more
>> permissive
>>
>
> Adding alternative interpolation functions, for example.
>

We can add a more sophisticated 'interpolate' function for this (if this
was ever requested)
Adobe/PDF certainly has other interpolation heuristics, but I have not
encountered any tools that used them. [1]


>
>>
>>> For an obscure feature like this, can't we afford to be more explicit.
>>> e.g. attach an interpolation() function to the color-stop before the
>>> interval we want to change the interpolation of?
>>>
>>
>> That is very confusing because the midpoint applies to the curve of both
>> color stops.
>>
>
> OK, then explicit interpolation() values between stops.
>

1: except when we do color management of the gradient ramp.