ISSUE-318: Hypothetical Render Model glyph copy assumes no sub-pixel positioning

HRM glyph copy assumes no sub-pixel positioning

Hypothetical Render Model glyph copy assumes no sub-pixel positioning

State:
CLOSED
Product:
TTML IMSC 1.0
Raised by:
Nigel Megitt
Opened on:
2014-05-22
Description:
IMSC 1 FPWD includes in the Hypothetical Render Model a test for how two glyphs can be considered identical for buffer copying purposes. This does not take into account sub-pixel positioning of anti-aliased text, which would result in different per-pixel buffer values for a glyph that would otherwise be considered identical using the current criteria.

For presentation devices that layout text using sub-pixel accuracy and render glyphs with anti-aliasing this test of identity will fail resulting in wrongly painted glyphs.

I propose that an extra criterion is added to the glyph identity test that the post-layout sub-pixel offset relative to the pixel grid, horizontally and vertically, is identical.

[1] https://dvcs.w3.org/hg/ttml/raw-file/ea1a92310a27/ttml-ww-profiles/ttml-ww-profiles.html#paint-text
Related Actions Items:
No related actions
Related emails:
  1. {minutes} TTWG Meeting 2015-10-29 (from nigel.megitt@bbc.co.uk on 2015-10-29)
  2. {minutes} TTWG Meeting 5/6/2014 (from nigel.megitt@bbc.co.uk on 2014-06-05)
  3. RE: {agenda} TTWG Meeting 5/6/2014 (from mdolan@newtbt.com on 2014-06-04)
  4. {agenda} TTWG Meeting 5/6/2014 (from nigel.megitt@bbc.co.uk on 2014-06-04)
  5. Re: ISSUE-318 (HRM glyph copy assumes no sub-pixel positioning): Hypothetical Render Model glyph copy assumes no sub-pixel positioning [TTML IMSC 1.0] (from glenn@skynav.com on 2014-05-29)
  6. {agenda} TTWG Meeting 29/5/2014 (from nigel.megitt@bbc.co.uk on 2014-05-28)
  7. Re: ISSUE-318 (HRM glyph copy assumes no sub-pixel positioning): Hypothetical Render Model glyph copy assumes no sub-pixel positioning [TTML IMSC 1.0] (from nigel.megitt@bbc.co.uk on 2014-05-27)
  8. Re: ISSUE-318 (HRM glyph copy assumes no sub-pixel positioning): Hypothetical Render Model glyph copy assumes no sub-pixel positioning [TTML IMSC 1.0] (from glenn@skynav.com on 2014-05-24)
  9. Re: ISSUE-318 (HRM glyph copy assumes no sub-pixel positioning): Hypothetical Render Model glyph copy assumes no sub-pixel positioning [TTML IMSC 1.0] (from nigel.megitt@bbc.co.uk on 2014-05-23)
  10. Re: ISSUE-318 (HRM glyph copy assumes no sub-pixel positioning): Hypothetical Render Model glyph copy assumes no sub-pixel positioning [TTML IMSC 1.0] (from pal@sandflow.com on 2014-05-23)
  11. Re: ISSUE-318 (HRM glyph copy assumes no sub-pixel positioning): Hypothetical Render Model glyph copy assumes no sub-pixel positioning [TTML IMSC 1.0] (from nigel.megitt@bbc.co.uk on 2014-05-23)
  12. RE: ISSUE-318 (HRM glyph copy assumes no sub-pixel positioning): Hypothetical Render Model glyph copy assumes no sub-pixel positioning [TTML IMSC 1.0] (from mdolan@newtbt.com on 2014-05-23)
  13. Re: ISSUE-318 (HRM glyph copy assumes no sub-pixel positioning): Hypothetical Render Model glyph copy assumes no sub-pixel positioning [TTML IMSC 1.0] (from nigel.megitt@bbc.co.uk on 2014-05-23)
  14. RE: ISSUE-318 (HRM glyph copy assumes no sub-pixel positioning): Hypothetical Render Model glyph copy assumes no sub-pixel positioning [TTML IMSC 1.0] (from mdolan@newtbt.com on 2014-05-22)
  15. Re: ISSUE-318 (HRM glyph copy assumes no sub-pixel positioning): Hypothetical Render Model glyph copy assumes no sub-pixel positioning [TTML IMSC 1.0] (from nigel.megitt@bbc.co.uk on 2014-05-22)
  16. RE: ISSUE-318 (HRM glyph copy assumes no sub-pixel positioning): Hypothetical Render Model glyph copy assumes no sub-pixel positioning [TTML IMSC 1.0] (from mdolan@newtbt.com on 2014-05-22)
  17. ISSUE-318 (HRM glyph copy assumes no sub-pixel positioning): Hypothetical Render Model glyph copy assumes no sub-pixel positioning [TTML IMSC 1.0] (from sysbot+tracker@w3.org on 2014-05-22)

Related notes:

Fixed at https://dvcs.w3.org/hg/ttml/rev/f7aca606db1d based on http://lists.w3.org/Archives/Public/public-tt/2014May/0156.html

Pierre-Anthony Lemieux, 24 May 2014, 01:29:36

Display change log ATOM feed


David Singer <singer@apple.com>, Nigel Megitt <nigel.megitt@bbc.co.uk>, Chairs, Thierry Michel <tmichel@w3.org>, Philippe Le H├ęgaret <plh@w3.org>, Atsushi Shimono <atsushi@w3.org>, Staff Contacts
Tracker: documentation, (configuration for this group), originally developed by Dean Jackson, is developed and maintained by the Systems Team <w3t-sys@w3.org>.
$Id: 318.html,v 1.1 2019/11/12 10:06:58 carcone Exp $