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.
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).
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 rpi-eink-api --restart=always --privileged
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.
POST http://rpi:5000
curl --form upload=@image.jpg --form resize=FIT --form background=WHITE http://rpi:5000 | jq
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. | No | Yes |
resize |
FIT Resize keeping aspect ratio, without croppingCROP Resize keeping aspect ratio, with croppingSTRETCH fill display, ignoring aspect ratioNONE 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 ~9 seconds.
Display update will be skipped if the resulting image is the same as the last request (see updated field in the response).
This endpoint only supports a single concurrent call in order to prevent simultaneous instructions being sent to the hardware.
GET http://rpi:5000
curl http://rpi:5000/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.
- It should be possible to update only part of the display if you are sending images where only a small amount of content changes each time. Currently, only clearing and refreshing the entire display is supported.