“Display regular photographs on a tri-color ePaper Display. You can get pretty good image quality and color variation by using a method called Floyd-Steinberg dithering, even with only three colors (red, white and black) on the ePaper Display!
I automated the image processing so that you can simply place regular image files in a folder, and the program automatically picks the next image to display and performs the necessary image processing required (on the fly) to render it on the ePaper Display. Here are some results!
A little background on ePaper Displays
I love the ePaper Display for its austere simplicity and elegance. The display persists even after the power is shutdown. The ePaper display can create highly detailed images with the contrast ratio and readability of printed material. The mechanics of the ePaper display are also quite fascinating in how the colors of the various pixels are manipulated to display the final image.
The ePaper Display I use is a tricolor one from Waveshare that can display white, black and red. I find the little pop of red quite useful in highlighting and providing some visual contrast and relief, as I have done in my International Space Station Tracker, Word Clock, and Weather Station projects. The tricolor display does not support partial updates, and as a result takes about 16 seconds for screen refresh - it is therefore suitable for projects where the display does not change that often. I find these challenges quite refreshing to overcome and am always thinking of new ways to harness the display.
The Waveshare ePaper library Display method takes in two Python PIL images as arguments - one to render the black pixels (all non-white pixels are rendered as black), and the other image to figure out which pixels are red (all non-white pixels in this second image are then rendered as red). It starts by flipping all the pixels to the “white” position, and then starts to flip all the black pixels to the “black” position from the first image. It then proceeds to process the second image, and flip all the non-white pixels there to the “red” position on the physical display to get the final image.”