There are four methods for implementing (multi)color in OpenType fonts:
* Apple's SBIX table - Embedded bitmaps, non-standard, used on OS X.
* Google's CBLC+CBDT - Embedded bitmaps, part of OpenType spec, used on Android.
* Microsoft's COLR+CPAL - Colored glyphs, part of OpenType spec, used in Windows.
* Adobe/Mozilla/W3C's SVG+CPAL - SVG in OpenType (SVGinOT), part of OpenType spec, works in Firefox/Thunderbird.
I chose to use SVGinOT because it is the only out-of-the-box option for color font support on Linux right now. I plan to make both CBLC+CBDT and SBIX versions in the future.
> I wish there was native support for this trend in Linux
There is an unmaintained patch for Cairo to support Google's bitmap CBDT+CBLC OpenType format.[1] It needs to be updated and completed for "official" Linux support.[2] Behdad has many other things to do, so please do not open an issue against that fork. Long term, I expect support for both CBDT+CBLC and SVGinOT.
> I wonder how difficult would be to copy all those images from the Apple font and create a custom TTF so I can get the fancy colored symbols in my computer.
It is possible to create a CBDT/CBLC version of the Apple Color Emoji font, but the font is, as you suspected, unlicensed[3].
There are four methods for implementing (multi)color in OpenType fonts:
* Apple's SBIX table - Embedded bitmaps, non-standard, used on OS X.
* Google's CBLC+CBDT - Embedded bitmaps, part of OpenType spec, used on Android.
* Microsoft's COLR+CPAL - Colored glyphs, part of OpenType spec, used in Windows.
* Adobe/Mozilla/W3C's SVG+CPAL - SVG in OpenType (SVGinOT), part of OpenType spec, works in Firefox/Thunderbird.
I chose to use SVGinOT because it is the only out-of-the-box option for color font support on Linux right now. I plan to make both CBLC+CBDT and SBIX versions in the future.
> I wish there was native support for this trend in Linux
There is an unmaintained patch for Cairo to support Google's bitmap CBDT+CBLC OpenType format.[1] It needs to be updated and completed for "official" Linux support.[2] Behdad has many other things to do, so please do not open an issue against that fork. Long term, I expect support for both CBDT+CBLC and SVGinOT.
> I wonder how difficult would be to copy all those images from the Apple font and create a custom TTF so I can get the fancy colored symbols in my computer.
It is possible to create a CBDT/CBLC version of the Apple Color Emoji font, but the font is, as you suspected, unlicensed[3].
[1]: https://github.com/behdad/cairo/tree/color-emoji
[2]: https://github.com/googlei18n/noto-emoji/issues/36
[3]: http://stackoverflow.com/questions/22337295/license-of-apple...