This is a proof-of-concept for a Protocol-buffer packed format for sprites: it isn't the format that Mapbox GL JS or Mapbox GL Native use. Instead, use spritezero, a library that creates a Mapbox-compatible format, or if you're using Mapbox Studio already, you don't need to install anything - our servers run spritezero already.
Assembles individual PNG sprite images to a Protocol Buffer-based format that includes metadata.
$ npm install -g spritenik
[...]
$ spritenik images/ > out.sprite.pbf
[...]
116 icons, 812 images total
$Individual images have to be in the following naming scheme: [name]-[size]@[ratio].png, with all but the name optional. If the -[size] part is missing, the size is automatically read from the image. If the @[ratio] part is missing, a pixel ratio of 1 is assumed. To specify SDF images, use -sdf instead of -[size].
Example: cinema-18@2x.png is an image named cinema that must be 18×18 pixels and a ratio of 2. Thus, the actual image dimensions must be 36×36 pixels.