[MPEG-OTSPEC] Call for Consensus RE: proposal: COLR extension

Renzhi Li Renzhi.Li at microsoft.com
Fri Oct 2 00:53:44 CEST 2020

I have an objection on a detail around the table describing data type LayerV1List, between line 99 and 100: From the description, the paintOffset field are an array of offsets to paints. However, in the column 1 it says "Paint" directly, which looks like the Paint records are directly embedded into the LayerV1List.

Please clarify whether the data type column for paintOffset field is incorrect, and if so, provide a correction of this.

From: mpeg-otspec <mpeg-otspec-bounces at lists.aau.at> on behalf of Levantovsky, Vladimir <Vladimir.Levantovsky at monotype.com>
Sent: Thursday, October 1, 2020 11:36
To: Peter Constable <pgcon6 at msn.com>; MPEG OT Spec list (mpeg-otspec at lists.aau.at) <mpeg-otspec at lists.aau.at>
Subject: [EXTERNAL] [MPEG-OTSPEC] Call for Consensus RE: proposal: COLR extension

Dear AHG members,

The proposal for extension of COLR table (introducing the new version1), developed as a collaborative effort of multiple members of this group, was presented this week and has been discussed in the GitHub repo (https://github.com/MPEGGroup/OpenFontFormat/issues/20<https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2FMPEGGroup%2FOpenFontFormat%2Fissues%2F20&data=02%7C01%7Crenzhi.li%40microsoft.com%7C4c84652ffea44b8d444908d866390131%7C72f988bf86f141af91ab2d7cd011db47%7C0%7C0%7C637371742311525183&sdata=JeyorpimAY%2FdVUjfJZ7HiSTENj%2FN6bE6w%2BNJ06hxBNE%3D&reserved=0>).

This email is a call for consensus to introduce this proposal to the SC29/WG3 and to recommend that this proposal, along with the some additional changes for font variations common table formats be considered by the WG as the basis for a new amendment to OFF standard (ISO/IEC 14496-22/AMD2).

To make sure that there is no confusion on how this work is going to proceed (if adopted) and what this call for consensus is seeking to achieve, please note that:

-          If our proposal and recommendations to start a new amendment are adopted, the WG will prepare and publish a new working draft of the future amendment. I will ask for this new working draft be made public so that the content of the changes and the technical details can be once again reviewed by the AHG, and we will be able to introduce new changes and corrections, if necessary.

-          This call for consensus is _not_ seeking for you to state your support for the proposed technical changes. I am asking for a _consensus to issue AHG recommendation_ that the new amendment work should be initiated based on these initial proposals. This recommendation (if the consensus is reached) will be recorded as part of the AHG report to the WG, which I prepare and present on this list for your final review and approval.

I’d like to ask you to voice your _objections_ (if any, stating your reasons for objection) to this call for a consensus recommendation to open a new work item. (If you want to voice your support for this new amendment, this is fine too, but not required for the purpose of this call.)

If I do not hear any objections by end of day Monday, Oct. 5th, I will prepare and submit the proposed technical changes as input contributions on behalf of AHG, and will prepare and share with you the AHG report summarizing the work conducted in this AHG and our recommendations to the WG.

Thank you,


From: mpeg-otspec <mpeg-otspec-bounces at lists.aau.at> On Behalf Of Peter Constable
Sent: Monday, September 28, 2020 5:22 PM
To: MPEG OT Spec list (mpeg-otspec at lists.aau.at) <mpeg-otspec at lists.aau.at>
Subject: [MPEG-OTSPEC] proposal: COLR extension

I’ve created an issue in the repo for discussion: Proposal: extension to COLR table (COLR v1)<https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fprotect-us.mimecast.com%2Fs%2FR_a_Cv2z58hWOA9EiQGuTI&data=02%7C01%7Crenzhi.li%40microsoft.com%7C4c84652ffea44b8d444908d866390131%7C72f988bf86f141af91ab2d7cd011db47%7C0%7C0%7C637371742311530195&sdata=fqz2MIK2%2BYfMovSJSSIqkNfKOobQifcfPl0OYZM7gio%3D&reserved=0>.

Google has prepared a proposal<https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fprotect-us.mimecast.com%2Fs%2FNoXmCwpA5KsL0yjvhqD-sg&data=02%7C01%7Crenzhi.li%40microsoft.com%7C4c84652ffea44b8d444908d866390131%7C72f988bf86f141af91ab2d7cd011db47%7C0%7C0%7C637371742311535181&sdata=%2FS1ivoXc30ynDnFc8MoZS9podXAbg60TD5QNaWgXXs0%3D&reserved=0> to extend the COLR table with significantly enhanced capabilities. This followed from initial discussion at a meeting in 2019 that included people from various companies, with a general consensus to proceed. I was commissioned by Google to adapt that into proposed revisions to the OpenType spec and to OFF.

Attached are preliminary drafts related to this:

  *   revisions to the COLR section—the bulk of the changes
  *   revisions to the Variations Common Table Formats section
  *   revisions to the CPAL section

Two variants for each are attached: one showing changes from OpenType 1.8.3, which would be approximately the same as changes from OFF:2019 + Amd1; and one showing the net result, with line numbering for easy reference.

Google and I are proposing that this be the basis for a proposed new edition of OFF.

Note: There is not a new edition in ISO's balloting process yet. That means that the technical content is not yet final, wrt ISO process. Assuming work on a new edition were approved at the next WG3 and SC29 meetings, technical balloting on the new edition would go well into 2021.

The draft for the proposed COLR table revisions is not yet complete, but there's enough in place that should allow a technical reader to get a pretty good understanding of proposed new structures and how they work. Also, the specifics on how the color gradation is calculated for a radial gradient have yet to be added, but the description of the structure used for it should, I think, give a clear idea of what the capabilities are. Some visual examples are forthcoming that will provide greater clarity.

The Google proposal was prepared by Behdad Esfahbod, Dominik Röttsches, and Rod Sheeter, with input and review feedback from several others including: Dave Crossland, Laurence Penney, Adam Twardoch, Cosimo Lupo, Rossen, Atanassov, Roel Nieskens, "Pomax", "bungeman", and myself. (Apologies if I missed anyone.)

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