Intent to Prototype: COLRv1 Color Gradient Vector Fonts
Dominik Röttsches
Contact emails
dr...@chromium.org
rshe...@google.com
cl...@google.com
Explainer & Specification
https://github.com/googlefonts/colr-gradients-spec/
https://github.com/googlefonts/colr-gradients-spec/blob/master/OFF_AMD2_WD.md#changes-to-off-5711---color-table
Design docs
https://github.com/googlefonts/colr-gradients-spec/
Summary
To solve problems with existing color font formats we designed a next generation font format suitable for web and system fonts called COLRv1 which enables powerful 2D graphics glyph definitions (gradients, transforms), supports variations, and reuses existing glyph contour definitions. Previous color font formats embed bitmap files into the OpenType font containers. They do not scale with high quality and have a large binary size. OpenType SVG embeds vectors and scales better but requires complex parsers and rasterisers and does not interact with OpenType variations.
Blink component
Blink>Fonts
Motivation
COLRv1 will allow smaller emoji files, reaching a size where it becomes feasible to use this type of color vector font as an emoji font format on the web. Together with the Google Fonts team we consider COLRv1 the prospective successor format for the Google Noto emoji font and a prototype of Noto emoji exists in COLRv1. COLRv1 addresses scaling fidelity issues with bitmap fonts (particularly when up-scaled to large font sizes or high resolution displays). In experiments we've seen that we can bring down the emoji font size to about a fifth while at the same time increasing rendering fidelity. The reduced emoji font file size is as long as every Unicode iteration brings a large increase in new emoji and emoji sequence combinations. The development of a new format was necessary to incorporate support for OpenType variations, overcome parsing complexity and file size issues over OpenType SVG.
The intent to prototype means the intent to include code in Skia and FreeType and in Blink to enable support for displaying fonts of this format when a respective flag is active.
TAG review
Currently only at the stage of publishing of Intent to Prototype.
Specification is developed outside of W3C, aiming for inclusion into the OpenType spec and ISO/MPEG Open Font Format.
TAG review status
Not applicable as different standards bodies? Feedback is welcome.
Risks
Interoperability and Compatibility
Feature adoption by other browsers has an influence on whether this format picks up traction.
The current spec and prototyping work includes publishing tools for font vendors to produce COLRv1 fonts based off of a set of SVG images, see https://github.com/googlefonts/nanoemoji
We are prototyping a version of Noto Color Emoji, Google's own emoji font to migrate to this format to save space and improve rendering quality.
Gecko: Under consideration
Edge: Positive
WebKit: No signal
Web developers: No signals
Feature adoption by other browsers has an influence on whether this format picks up traction. The current spec and prototyping work includes publishing tools for font vendors to produce COLRv1 fonts based off of a set of SVG images, see https://github.com/googlefonts/nanoemoji We are prototyping a version of Noto Color Emoji, Google's own emoji font to migrate to this format to save space and improve rendering quality.
Gecko: Under consideration
Edge: Positive
WebKit: No signal
Web developers: No signals
Is this feature fully tested by web-platform-tests?
Partially, likely the majority of testing will be performed at a lower level such as in FreeType and Skia rasterisation tests. WPT pixel tests will be added to provide a basic sanity check.
Tracking bug
https://bugs.chromium.org/p/chromium/issues/detail?id=1170733
Link to entry on the Chrome Platform Status
https://chromestatus.com/feature/5638148514119680
一丝
Dominik Röttsches
On Tuesday, January 26, 2021 at 3:59:15 PM UTC+2 Dominik Röttsches wrote:
TAG review
Currently only at the stage of publishing of Intent to Prototype.
Specification is developed outside of W3C, aiming for inclusion into the OpenType spec and ISO/MPEG Open Font Format.TAG review status
Not applicable as different standards bodies? Feedback is welcome.
Please note that the TAG regularly reviews specs from outside W3C, e.g. WHATWG, TC39, IETF etc, even some early proposals that have not yet found the right venue. So, while TAG review is certainly not required, none of these are reasons that preclude it.
Lea Verou
TAG review
Currently only at the stage of publishing of Intent to Prototype.
Specification is developed outside of W3C, aiming for inclusion into the OpenType spec and ISO/MPEG Open Font Format.TAG review status
Not applicable as different standards bodies? Feedback is welcome.