Apple supports image-based fonts (that’s how their emoji font was made), but the font can only be used in Apple devices. The manual explains how to do it in chapter 13.4 Apple Color Fonts. Also see how to use images in general in chapter 3.10 and 6.7.
Glyphs 1 used to support a thing called Photofont which you can use in Adobe apps and Quark, but the font user needs to install a plugin for them. Depending on how you are going to use the font and the supported resolution (which is probably larger than 512*512), it can be a viable option. Glyphs no longer supports it, so you need to use the tool called BitFonter.
Is can provide the PhotoFont plugin if needed. The problem is that the plugins to use PhotoFonts in Adobe apps are very old. I didn’t check the latest supported version. And the handling was more like text layers in Photoshop 4 where you get a dialog with a plain text field and that would render an image like object. So no proper text flow and styles.
In which OS X are you testing? The implementation has changed in recent versions. And it was not always clear what caused the Mac to respect the kerning, and what it caused to not respect it when it happened. There was reason to believe that some versions require at least one other GPOS feature present in the font, e.g., cpsp. If you dig around in the forum archives, you may find something about it. In any event, there is insufficient documentation from Apple. It would not surprise me if kerning did not work at all for sbix bitmaps.
The starting objective of: [quote=“notanotherfolio, post:1, topic:4047”]
hi-res photos of the letters that will make up the font
Which ended up in a 512X512 px Apple color font… May lead you to consider a different solution with “vector-halftone” effect that can provide very close look of what you’re trying to achieve by Apple Photo font; while you can still enjoy the rich capabilities of OT/WOFF.
Such as fonts showcases via the following link: https://creativemarket.com/tag/brush%20font