[MPEG-OTSPEC] Requesting progress update on COLRv1 in fontTools, FreeType, etc.

[William_J_G Overington]

Hi Peter

Thank you for explaining.

I had been thinking about it further and I had decided that your idea 
was a much better way to do it. I was about to post to say so when I saw 
your later post.

Just to round things off.

> Would this be just to set the values to a default (since you mention a 
> default in your other message)?

Yes.
If I have understood what you have written I get the impression that 
implementing your idea might also have problems, except perhaps for 
printing of a hardcopy document directly from the application program, 
though perhaps it might also be possible to be useful if one makes an 
SVG graphic, converting text to curves and then importing the graphic 
and including it in a PDF document. This would depend upon the 
application, but, use for, say, a decorative border for a poem might be 
useful. So I hope that your idea will become widely implemented. Maybe 
it will become a widely used technique and that my suggestion will 
simply be a like booster rocket that led to your idea being published 
and discussed and implemented.
Anyway, thank you again for replying to my ideas and to my comments. I 
have enjoyed discussing it all and I feel that I have learned a lot.
Best regards,
William Overington
Friday 22 January 2021


------ Original Message ------
From: "Peter Constable" <pgcon6 at msn.com>
To: "William_J_G Overington" <wjgo_10009 at btinternet.com>; 
"mpeg-otspec at lists.aau.at" <mpeg-otspec at lists.aau.at>
Sent: Friday, 2021 Jan 22 At 20:02
Subject: RE: [MPEG-OTSPEC] Requesting progress update on COLRv1 in 
fontTools, FreeType, etc.


William

It would be relatively quite easy for the creator of a font development 
tool to add UI for the font designer to specify colours for your “dec 
col 1”, etc. However, I thought the point was to have colours that can 
be controlled by the end  user, not the font developer. Would this be 
just to set the values to a default (since you mention a default in your 
other message)?

Assigning colour values to FFFD and FFFE would be problematic. In the 
case of FFFF, no colour value is specified in the font at all, and that 
is a necessary assumption. The reason is that, if a value were specified 
in the font for FFFF,  it would imply that there must be 65536 entries 
in every CPAL palette. That would be extremely wasteful. Because FFFF 
refers to a colour that is only specified _outside the font_, there is 
no need to have for FFFF to be a valid index into the color  record 
array. The same would apply to FFFD and FFFE: If you want to give FFFD a 
special meaning but also allow the font creator to assign a default 
colour that gets recorded in the font, then it would have to be recorded 
in the 65534th color record.  Either that, or else the formats would 
need to be changed to add special fields in the CPAL table that store 
only the “dec col 1” etc. values.

But this still doesn’t address the problems that exist for users. With 
FFFF, a content author specifies text foreground colour in their 
content. Every document format that supports rich (styled) text will 
include some means of storing the  text foreground colour styling. If a 
content author needs to specify “dec col 1”, etc., then not only do font 
specs need to define that but now content formats also need to define a 
way for that author-determined information to be conveyed as part of the 
content;  and applications for viewing the content would need to support 
that. For example, CSS would need a way to specify “dec col 1”, and 
browsers would need to read and apply it when displaying text with a 
colour font. IOW, you’d have to sell your idea to a lot  of other groups 
than just those involved in defining OFF or OpenType.

For a spec like CSS that gets used in many contexts and implemented in 
many applications, selling that would be an uphill challenge. For an app 
that uses a proprietary content format, e.g., Affinity Designer 
(ignoring for the moment any  export to other formats), because they own 
their proprietary format there isn’t a need for industry-wide agreement 
on interoperable formats. But then we’re into a scenario in which it 
would make just as much sense for the app to give the content author 
complete  control over the colour palette used by a given font. The cost 
for them to create the UI and define ways in their document format to 
represent the choices are comparable.



Peter



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