When building the font, images are composited onto a slightly
rectangular canvas that's 4 pixels wider on the left and right.
The thumbnails though are required to be 72x72, i.e. square.
In order that they look the intended size we need to crop off
the margins that were added earlier.
Same problem that we ran into previously with the emoji font--
imagemagick takes RGBA that contain only grayscale and converts
to grayscale with alpha, but although it can display these ok,
chrome can't. So force it to generate RGBA output.
Thumbnail generation for Unicode requires some changes:
- 72x72 images (exact, not just fit within that frame)
- custom prefix ending in underscore
- images for unsupported flags
The default build doesn't support some flags by default, since they
are not wanted by Android. For the thumbnail list these images need
to be provided, so we alias them to the unknown flag images as that's
what would show for them. It's probably a good idea to list these
explicitly anyway, other tools could use this information.
To generate the Unicode comparison page of various vendor emoji,
Unicode prefers to use 72x72 images for all the supported emoji
without aliasing. This tool will generate these from the
directory of cleaned images produced by the emoji build, using
the aliases defined in emoji_aliases.txt.
Mike FABIAN