Re: [office] Draft for enhanced colors

[Regina Henschel <regina.henschel@libreoffice.org>]

Hi Francis,

Francis Cave schrieb am 29.03.2023 um 19:26:
> Hi Regina
>
> Sorry, this is not my area of expertise, so I may well be asking naÃve questions!

This is an early draft and only a part of the total work. So please ask 
whenever something is not clear.

> I'm trying to see how this fits into the existing schema. All the elements in your proposal appear to be new.

Yes.

 I appreciate that this is an early draft,

I have attached the complete work now. That is an early draft too, but 
might give you a picture of the intended changes.

 but I see that you expect the enhanced colour model to be available in 
four contexts:
> - <draw:gradient-stop>
> - <style:fill-enhanced-color>
> - <style:stroke-enhanced-color>
> - <style:char-enhanced-color>.

Yes.
> Should <draw:gradient-stop> be <draw:gradient-step>?

The <draw:gradient-stop> is the same for <draw:gradient> as the 
<svg:stop> for <svg:linearGradient> and <svg:radialGradient>. It allows 
gradients based on more than two colors. It is the same as <gs> in 
<gsLst> in OOXML.

You can have one gradient with transitions from red over yellow over 
green to blue, for example.

Because of the risk of confusion with draw:gradient-step-count, I have 
advised the developer not to use <draw:gradient-step>. "stop" is used 
because that is used in OOXML and SVG terminology.

 I ask, because there is an existing attribute 
draw:gradient-step-count, which might be related, and I don't understand 
that meaning of "stop" in this context.

The attribute draw:gradient-step-count tells, whether the gradient is 
smooth or stepped. Stepped gradients do neither exist in SVG nor in OOXML.

> What do you imagine would be the parent elements of the above four elements?

<draw:gradient-stop> is part of a gradient definition in <draw:gradient> 
element.
<draw:fill-complex-color> and <draw:line-complex-color> (as I have named 
it in my current version) will become child elements of 
<style:graphic-properties>
<draw:char-complex-color> will become child element of 
<style:text-properties>

Using such complex color model is currently not planned for further 
objects. But my intension it to define these complex colors in such a 
way that they can easily be used for other objects, e.g. page 
background, which would be <style:page-layout-properties>.

> If fills, strokes and chars can have enhanced colors, are there other contexts in which enhanced colours could be used, such as extrusion, or the color of a material in the dr3d namespace?

As <extrusionClr> in OOXML can be <schemeClr> with e.g. <lumMod> child 
element, it is likely, that such color model will be used for extrusion 
too. The current simple color is a draw:secondary-fill-color attribute 
in <style:graphic-properties>. So it would likely become 
<draw:secondary-fill-complex-color> element in <style:graphic-properties>.
The color of material of 3D-objects is part of 
<style:graphic-properties>, so already covered.
Use for the lights of a 3D-scene (those would be in dr3d namespace) is 
unlikely.

> I appreciate that an important purpose here is to increase interoperability with OOXML, but should we stop there or be looking for a more comprehensive enhancement?

I have tried to build it so, that extending is easily possible if 
developers/users of an ODF application need further color spaces, color 
notations or color transformations. LO is not working on such, however 
CSS-like extensions might be useful for online office-applications, for 
example. But I do not want to be proactive without a real demand.

If Microsoft wants to add other then the suggested RGBHex, RGBZeroToOne 
and Scheme types for their export to ODF [hallo Alfred ;)], that can 
easily be integrated.
The color transformations are implementation-defined anyway in my 
proposal. OOXML does not describe the algorithm clear enough so that 
implementers ask in Microsoft forums. [e.g. 
https://social.msdn.microsoft.com/Forums/sqlserver/en-US/eb151eb0-e539-4f12-a453-1ff46dc28578/satmod-satoff-documentation?forum=os_binaryfile]

Kind regards,
Regina

> Kind regards,
>
> Francis
>
>
>
> -----Original Message-----
> From: office@lists.oasis-open.org <office@lists.oasis-open.org> On Behalf Of Regina Henschel
> Sent: Wednesday, March 29, 2023 5:38 PM
> To: office@lists.oasis-open.org
> Subject: Re: [office] Draft for enhanced colors
>
> Hi Francis,
>
> Francis Cave schrieb am 29.03.2023 um 16:51:
> > Hi Regina
> >
> > I am unclear as to which new elements and new attributes are in the 'style' namespace and which are in the 'draw' namespace.
>
> My intension was to have them all in namespace "style". That means <style:color-transform> element with style:transform-type and style:transform-value attributes, and <style:enhanced-color> element with style:color-type and style:color-value attributes.
>
>    For example, on page 3 I get the impression that you were maybe undecided as to whether the attribute is style:color-value or draw:color-value. But I may be misinterpreting something.
>
> That are simple editing leftovers I didn't notice.
>
> But if you think all or some of those would better use "draw" namespace, that is OK for me.
>
> With my other new elements it is the same problem. There will come <gradient-stop>, <char-complex-color>, <fill-complex-color> and <stroke-complex-color> elements which use the <style:color-transform> and <style:enhanced-color> elements as child elements.
>
> It would be good to get some guidance in respect to namespaces.
>
> Kind regards,
> Regina
>
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Attachment: ODF draft multi-color gradient plus theme v1.odt
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