eInk Display Server

A small NodeJS based server to serve local or public images optimized for common eInk Displays (e.g. from Waveshare) in combination with a WiFi-enabled microcontroller (e.g. esp32, esp8266).

Important: This is only the server part. You will need to program your microcontroller yourself so it fetches images from this server using TCP/IP.

Images are converted to BMP and translated into black and white "grayscale" using Floyd Steinberg dithering.

Support for Docker is available and the recommended way of deploying.

Supported services / sources

Currently two services have been implemented:

1. Local files

This service picks a random picture from a local folder (including subfolders). Supported image types are: bmp, jpeg, png, tiff and heic.

Endpoint: /local.bmp

2. Wallhaven Wallpapers

This service downloads a random desktop wallpaper from Wallhaven.cc and converts it.

Endpoint: /wallpaper.bmp

Usage (Docker)

Configuration

The server listens on port 3000 and individual configuration is done using environmental variables, all of which are optional and have reasonable defaults. You probably want to adapt EINK_WIDTH and EINK_HEIGHT to match your specific display. The following options are available:

Environmental Variable	Required	Default	Description
EINK_WIDTH	false	800	Display width in pixels. Used to scale the original image up or down to this width.
EINK_HEIGHT	false	480	Display height in pixels. Used to scale the original image up or down to this height.
LOCAL_FOLDERS	false	/images	Comma separated list of folders to include in local image list
LOCAL_EXCLUDE	false	empty	Comma separated list of (sub-)folder names to be excluded from LOCAL_FOLDERS
LOCAL_SHOW_HIDDEN	false	false	Wether to use hidden files (=starting with a dot) in LOCAL_FOLDERS.

Run Docker container

Run with defaults

This will make the server available on port 3000 on the host machine.

docker run -d \
    -p 3000:3000
    --name eInkServer \
    tfohlmeister/eink-display-server:latest

You can then load an eInk-optimized version of a random wallpaper at http://$HOST_IP:3000/wallpaper.bmp.

Advanced examples

This command will mount a local image folder /path/to/local/images:

docker run -d \
    --name eInkServer \
    -p 3000:3000 \  
    -v /path/to/local/images:/images \
    tfohlmeister/eink-display-server:latest

The following command will mount two local image folders and excludes all folders called PrivatePictures:

docker run -d \
    --name eInkServer \
    -p 3000:3000 \
    -v /path/to/local/images1:/images/images1 \
    -v /path/to/local/images2:/images/images2 \
    -e LOCAL_FOLDERS=/images/images1,/images/images2 \
    -e LOCAL_EXCLUDE=PrivatePictures \
    tfohlmeister/eink-display-server:latest

You should now be able to also display eInk-optimized versions of your mounted images at http://$HOST_IP:3000/local.bmp.

Troubleshooting

If you see Watcher Errors in the log stating the system limit for number of file watchers reached, you need to increase the amount of inotify watchers on your (host) system. Restart the application afterwards.

If you found a bug or find this project is missing a feature please create an Issue.

Development

1. Install dependencies

npm install

2. Develop with auto-compiling and debugging enabled

npm run watch-debug

3. Build server and container

npm run build
docker build --tag eink-display-server:latest .