I have experimented a little today with displaying greyscale image on a 2.7" 176x264 pixel ePaper display using Floyd Steinberg dithering.
It works well on ePaper displays, there follows some screenshots (each image is 176x264 pixels):
- Top left is the classic image processing picture of Lena Söderberg in 8 bit grey-scale (255 levels + black)
- Top right is an image using a simple threshold of 128 (pixels with grey-scale value less than128 = black)
- Bottom left is using the dithering, all pixels are black or white but the eye averages the density
- Bottom right is an experimental algorithm with contrast stretching
Sketch to follow (only uses drawPixel) when I have made it more presentable!
This is a test pattern showing how the dot density changes compared with a grey-scale image on the right, there are some artifacts that more sophisticated approaches eliminate.