Color fonts technology in OFF

[Levantovsky, Vladimir]

Dear AHG members,

For the last couple of years we've seen a steady increase of attention given to color font initiatives. By mid-2011, the general discussions materialized into more structured approach that resulted in the creation of the W3C Community Group [1] that explored the ways how SVG-based glyph descriptions can be integrated within the OFF format utilizing OFF layout and text shaping (something that we've been watching and discussing on this list as well), and we've seen a significant spike in color font related developments with the recent announcements from Google [2,3] and Microsoft [4,5].

It seems that the time has come for this group and ISO SC29/WG11 to address these issues formally, and the first necessary step of the process would be to prepare and publish a Call for Proposals with the purpose to collect information on the existing technology and evaluate them for inclusion in the next version OFF standard (ISO/IEC 14496-22). In order to accomplish this, I would like to start collecting the use cases and requirements for color font technology, something that will become either an integral part of the Call for Proposals or a standalone document the CFP will reference.

To start the discussion, I would like to suggest that we should categorize and sort the requirements along the following lines (these were brought up and discussed in various forums and private discussions, and I am summarizing the results without taking any credit):

-          Expressiveness / richness of the design canvas that a future solution would offer to font developers - we probably need to consider whether some minimal requirements should be defined to satisfy the existing and foreseeable use cases.

-          Compatibility and ease of integration of the newly proposed technologies with the existing OFF glyph description / text layout mechanisms - we need to make sure that new glyph description mechanism  can be seamlessly integrated with the existing layout / composition model, and we also need to consider the need for graceful degradation of font performance when the same font is rendered in different environments that may or may not support new functionality and features.

-          Consideration should be given to potential penalties of introducing the new functionality - fonts often used in resource constraint environments and font size inflation(as a results of adding new glyph description mechanism) may be prohibitive in some cases.

-          Consider the rendering environments and device capabilities - things that can be done in a web browser running on PC or tablets may differ significantly from what can be achieved when a font is rendered in resource-constrained devices such as consumer appliances.

-          Scalability and co-existence of the various approaches (also considering previous points on compatibility and resource constraints) - we may have good reasons to consider how various approaches for color font implementation can co-exist peacefully (either similar to currently implemented embedded bitmaps / scalable outline solutions, or the need to provision for multiple color font profiles, or both).

Like I said, these are just starting points that need to be addressed in order to prepare and issue a Call for Proposals. The next WG11 meeting is coming up in the end of July (the week of July 28th) and it would be desirable if we can publish the CFP (or at least a reasonably complete draft CFP) by the end of the meeting. Therefore, your active participation is encouraged and very much appreciated.

Thank you,
Vladimir

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[1] http://www.w3.org/community/svgopentype/
[2] https://color-emoji.googlecode.com/git/specification/v1.html
[3] https://code.google.com/p/color-emoji/
[4] http://tech.groups.yahoo.com/group/mpeg-OTspec/message/986
[5] http://channel9.msdn.com/Events/Build/2013/3-191

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