picam

Raspberry Pi Camera image collector and processing server

Introduction

Collect images from a pi-camera on the pi, send those images to a remote server for storage. Maximum resolution for a Logitech QuickCam Pro is 800 x 600, the camera software used, however, is not limited to the QuickCam Pro.

To enable the oled screen, enable I2C in raspi-config.

Architecture

The system consists of two primary components:

1. Client: Runs on the Raspberry Pi. A shell script (imager.sh) captures images periodically. A Go binary (client_main/client) watches the local storage directory and streams new images to the remote server over gRPC.
2. Server: Runs on a central machine. It accepts incoming images from authenticated clients and saves them to a designated storage directory per client.

Dependencies

Software to install includes:

• golang
• grpc libraries

For the OLED display (optional):

• apt-get install build-essential python3-pip python3-dev python3-smbus python3-pil
• pip3 install Adafruit-Blinka adafruit-circuitpython-ssd1306

Hardware required:

• raspberry pi - Tested on at least pi4.
• usb webcam - Tested, but probably any usb cam.

Server Operations

The server expects a text protobuf configuration file (config.textpb) that defines its listening port and the client mappings.

Example config.textpb:

port: 9987
client:{
  id: "abc12345"
  store: "/tmp/store1"
}

Running the server:

go run server/main.go -config /path/to/config.textpb

The server process typically runs at system startup from a systemd file.

Client Operations

The client watches a local directory and uploads new files to the server.

Starting the client:

go run client_main/main.go -id "abc12345" -store /tmp/camstore -server docs.as701.net:9987

Actuation of the image capture is done through cron. For example:

  # m h  dom mon dow   command
  # Run the image collection script.
  * * * * * /home/pi/scripts/git/picam/client/imager.sh >> /tmp/capture.log 2>&1
  # Remove stale/old images from the collection bin (/tmp/camstore)
  1 * * * * find /tmp/camstore -type f -ctime +1 -exec rm {} \; >> /tmp/cleanup.log 2>&1

For OLED display usage, simply make a cron entry to update the screen:

0 * * * *  /home/pi/scripts/git/picam/client/oled.py >> /tmp/oled.log 2>&1

Systemd and Unique Client IDs

The client_main typically runs at system startup via a systemd script. Every client device communicating with the server must have a unique ID that matches the server configuration.

To preserve client privacy while maintaining a unique identifier per device, we recommend two simple approaches for your client-side systemd service (img_client.service):

Option 1: Static Environment File (Recommended)

Generate a unique UUID at provisioning time and store it in /etc/default/picam-client:

echo "PICAM_CLIENT_ID=$(uuidgen)" | sudo tee /etc/default/picam-client

Then reference it in your systemd service file:

[Service]
EnvironmentFile=-/etc/default/picam-client
ExecStart=/home/pi/scripts/git/picam/client_main/client -id ${PICAM_CLIENT_ID} -store /tmp/camstore -server docs.as701.net:9987

Option 2: Dynamically Derived ID

If you prefer not to manage static files on each client, you can derive a hashed identifier from the machine ID dynamically on execution using ExecStartPre:

[Service]
ExecStartPre=/bin/sh -c 'echo PICAM_CLIENT_ID=$(cat /etc/machine-id | sha256sum | head -c 16) > /run/picam-client.env'
EnvironmentFile=/run/picam-client.env
ExecStart=/home/pi/scripts/git/picam/client_main/client -id ${PICAM_CLIENT_ID} -store /tmp/camstore -server docs.as701.net:9987

Be good