Intro
A while ago, our little one was born. As unfortunately her (great-)grandparents are located somewhat spread out over the globe, real-life visits can't happen too often. Obviously, video calling is a thing nowadays, so we keep in contact. Still, I wanted everyone to also be able to see her when we weren't online together. So I thought: why not make a picture frame around a color display and a WiFi chip? Especially with the little one growing so fast, it would be nice to send a new photo every day and have it always show a new and up-to-date picture.
You probably have seen E-ink displays by now: if not in an Ebook-reader, then surely in some local supermarket or other shop where they replaced the old paper price tags. They're great for displaying static images as they retain their most recent image without any power draw. Most of these screens are black-and-white, with sometimes red or yellow thrown in as an extra colour for good measure. These are nice, but a black-and-white picture doesn't do justice to the vibrant colors of a happy baby derping around with her colorful toys.
At the point of writing (early 2023), some E-book-readers with color screens are finally starting to appear. The quality of them seems good, with colors approaching those of a newspaper. Unfortunately, they are expensive, and the screens themselves don't seem to be available as spare parts yet, so there's no chance of easy re-use in a DIY project.
However, there has been one type of color E-ink display that has been available for use in DIY projects. It seems mostly sold by Waveshare, a Chinese company catering to the maker market, and the most common one is a 5.65 inch 7 color 640x448 unit. With only 7 colors and a refresh time of about a minute, it seems intended to be the 'big brother' to those price tags: displaying static information with the colors used to e.g. have some flat background colors. They're certainly not intended to reproduce photorealistic images.
That is a bit unfortunate: an Eink display makes for a great 'printed photo' simulacrum as it doesn't require any backlight and is entirely static. I'm not the only one who thinks so, and a fair amount of people already had an attempt at using dithering to make this screen into something that can display pictures with some fidelity. This is my attempt at doing so.
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