> … it’s not clear how a typical user would have gotten a scanned photograph of a baby onto a Mac in 1984.

Image digitizer existed for Macintosh and other computers. Some examples:

• MicronEye, from Micron Technology, Inc. https://archive.org/details/MacWorld8409SeptemberOctober1984...

• MacVision, from Koala Technologies Corp. https://archive.org/details/MacWorld_8412_December_1984/page...

• MAGIC, from New Image Technology, Inc. https://archive.org/details/MacWorld_8412_December_1984/page...

• Micro-Imager, from Servidyne Systems, Inc. https://archive.org/details/MacWorld_8412_December_1984/page...