A typeface of bitmaps but not a bitmap font

I want to make a typeface from scanned greyscale images. I’m not bothered about scalability as it will be used at a single size for a book. But I would like to have control over placement of the image and metrics. I’ve never done this before, but from what I can see from the color font tutorial, it seems convoluted: a bit like painting your hallway through the letterbox. Does anyone know of an easier way? Also: I would like to use 4 images of each letter and add code to randomise selection. Does anyone know if this can actually be done?

You should look at this https://glyphsapp.com/tutorials/creating-an-apple-color-font (this could be a bit more user friendly, I know.)
And this: https://glyphsapp.com/tutorials/features-part-3-advanced-contextual-alternates

thanks, I think I’m starting to understand how to control placement and metrics using the master layer. Can contextual alternates be done with bitmaps, as they can with vectors?

The context features work the same.

In which context (which app) does your font have to work? sbix does not work everywhere.

probably InDesign

But you can build an SVG font from the setup.

I need a font of greyscale bitmap images, with 4 versions of each letter and code to do the random swapping (contextual alternates). It will probably be used in InDesign. Can you advise me as to the best way to approach this? Should I follow the Apple Color Font process as detailed in the tutorial you have already linked, then add the feature code, then export? Is there anything else you think I should know?

Yes. But try with one glyph first, and see if everything you envisioned actually works the way you expect. PDF creation? Printing? Anything you need.