ISSUE-210: The values for alpha in rgba() don't correspond to CSS3 Color definitions

rgba() alpha value space

The values for alpha in rgba() don't correspond to CSS3 Color definitions

State:
OPEN
Product:
TTML2
Raised by:
Glenn Adams
Opened on:
2013-05-15
Description:
As presently defined, we allow the alpha value in an rgba() tuple to take a value from 0 to 255, rather than 0.0 to 1.0 (or 0% to 100%) as defined in CSS3 Color. On the other hand, we do use the CSS3 Color alpha values of 0.0 to 1.0 for opacity. This creates a bit of an anomaly if we should want to define tts:color in terms of CSS3 Color's definition of 'color'.

I'm presently marking this for TTML1.0, if we want to address in TTML10SE. Otherwise, we should push out to TTML.next.
Related Actions Items:
No related actions
Related emails:
  1. {minutes} TTWG Meeting 2015-02-05 (from nigel.megitt@bbc.co.uk on 2015-02-05)
  2. {agenda} TTWG Meeting 2015-02-05 (from nigel.megitt@bbc.co.uk on 2015-02-04)
  3. {agenda} TTWG Meeting 2015-01-29 (from nigel.megitt@bbc.co.uk on 2015-01-28)
  4. {agenda} TTWG Meeting 2015-01-22 (from nigel.megitt@bbc.co.uk on 2015-01-21)
  5. {agenda} TTWG Meeting 2015-01-15 (from nigel.megitt@bbc.co.uk on 2015-01-14)
  6. CORRECTION to {minutes} TTWG Meeting 28/10/2014 (from nigel.megitt@bbc.co.uk on 2014-11-21)
  7. RE: {minutes} TTWG Meeting 27/10/2014 (from nigel.megitt@bbc.co.uk on 2014-10-29)
  8. {minutes} TTML Meeting of 24/10/13 (from glenn@skynav.com on 2013-10-24)
  9. RE: TTML Agenda for 24/10/13 (from mdolan@newtbt.com on 2013-10-23)
  10. TTML Agenda for 24/10/13 (from nigel.megitt@bbc.co.uk on 2013-10-23)
  11. RE: ISSUE-210 (rgba() alpha value space): The values for alpha in rgba() don't correspond to CSS3 Color definitions [TTML 1.0] (from Sean.Hayes@microsoft.com on 2013-05-17)
  12. ISSUE-210 (rgba() alpha value space): The values for alpha in rgba() don't correspond to CSS3 Color definitions [TTML 1.0] (from sysbot+tracker@w3.org on 2013-05-15)

Related notes:

Postpone a resolution for this issue to TTML.next.

Glenn Adams, 27 Jun 2013, 15:48:10

Glenn: P2

Philippe Le Hégaret, 24 Oct 2013, 15:34:34

Address this in the HTML/CSS mapping section.

Glenn Adams, 14 Sep 2014, 13:40:50

Take no action to syntax or semantics of alpha. Simply deal with this in the process of mapping to XSL-FO or HTML/CSS, etc.

Glenn Adams, 14 Jan 2015, 06:21:48

[nigel]: [meeting 2015-02-05] Resolution is to add an editorial note to readers highlighting the difference in scale of alpha value.

5 Feb 2015, 15:42:55

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David Singer <singer@apple.com>, Nigel Megitt <nigel.megitt@bbc.co.uk>, Chairs, Thierry Michel <tmichel@w3.org>, Philippe Le Hégaret <plh@w3.org>, Staff Contacts
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