A rest API for setting the display image on a Waveshare 4.26" eink HAT connected to a Raspberry Pi. Supports scaling and rotating the input image. Endpoints are also provided for fetching display contents and clearing the display.
This project utilises the Waveshare e-paper SDKs for handling the device commands. This SDK does not seem to have any official documentation, the API usage was obtained from these pages:
For convenience, this tool is packaged as a docker container. It can also be run on bare metal, but you will need to add the Waveshare SDK to your path (see Dockerfile).
epd object is used across requests, therefore it is not possible to run this application
on a webserver with more than a single worker, should you choose to use a webserver other than the Flask development
webserver.
Build and run the container:
git clone https://github.com/adriankeenan/rpi-epaper-api.git
docker build -t rpi-eink-api .
docker run -p 5000:5000 --restart=always --privileged rpi-eink-api
Now you're ready to send images to the display!
--restart=always will ensure that the container is restarted on crash and on system boot.
You can run also run the API locally using the EPD_MOCK=true env var to mock all calls to the display itself.
You can still check that the correct image is produced by looking at src/img.png.
EPD_MOCK=true python3 src/server.py
POST http://rpi:5000
Set image from file
curl --form [email protected] --form resize=FIT --form background=WHITE http://rpi:5000
Set image from pipe
cat image.jpg | curl --form image=@- --form resize=FIT --form background=WHITE http://rpi:5000
Data should be sent form-encoded.
| Field | Description | Default | Required |
|---|---|---|---|
image |
Image file to display. Any image type supported by the Python PIL library should work. | N/A | Yes |
mode |
Display mode, corresponding to the display_XXX method on the epd object.FAST - uses display_Fast for a complete screen refresh.4GRAY - uses display_4Gray in order to display an image in black, white and 2 shades of grey.PARTIAL - uses display_Partial for incremental updates (which may cause ghosting). |
FAST |
No |
dither |
Whether to enable dithering when converting image to mono or 4 gray palette. true or 1 to enable. |
true |
No |
resize |
FIT Resize keeping aspect ratio, without cropping.CROP Resize keeping aspect ratio, with cropping.STRETCH fill display, ignoring aspect ratio.NONE Display without any scaling, pixels drawn 1:1. |
FIT |
No |
rotate |
Number of degrees to rotate counter-clockwise, supports increments of 90 degrees. | 0 |
No |
background |
Background colour to use if the image doesn't fill the display. Either WHITE or BLACK. |
WHITE |
No |
Expect this call to take ~5 seconds.
Display update will be skipped if the resulting image is the same as the last request (see updated field in the response).
GET http://rpi:5000
curl http://rpi:5000 -o img.png
Returns the last image (as PNG) that was successfully sent to the display. This is the exact framebuffer sent to the device (eg post-scaling). This is useful for checking the scaling and rotation settings are correct.
This image is not persisted between restarts of the container.
DELETE http://rpi:5000
curl -X DELETE http://rpi:5000
Expect this call to take ~7 seconds.
Reverts all pixels to the off (white) state.
- Although this is project is intended only for the 4.26" e-paper display, it's likely that other displays can be supported by changing the imported EDP object.