unique_colors
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Written by Larry Bank
Project started July 24, 2025

An optimized utility designed to count the number of unique colors presesnt in PNG
images. The purpose is to provide optimized images for the TRMNL devices. The current
focus is to avoid sending 2-bit grayscale images when the same image can be represented
as a 1-bit image. This will allow the latest TRMNL devices to use the new image for
a partial (non-flashing) update. It is certainly possible for the TRMNL's ESP32 to
do this same function before doing an update, but it's more efficient (for battery life)
to have this done on the server.