Screenshot Server for Legacy Devices

This Docker container captures screenshots of a webpage at configurable intervals and serves them via a simple web interface, perfect for displaying on older devices that can't handle modern web technologies.

Quick Start

1. Build and run with Docker Compose:

docker-compose up -d

2. Access the screenshot viewer at:

http://localhost:8080

Using from Docker Hub

services:
  screenshot-server:
    image: flucko/screenshot-server:latest
    ports:
      - "8080:80"
    environment:
      - TARGET_URL=http://example.com/
      - RESOLUTION=1024x768
      - SCREENSHOT_INTERVAL=60
    restart: unless-stopped
    volumes:
      - screenshot-data:/var/www/html

volumes:
  screenshot-data:

Configuration

Edit the environment variables in docker-compose.yml:

Variable	Default	Description
TARGET_URL	http://192.168.0.121:8180/	The webpage to capture
RESOLUTION	1024x768	Screenshot resolution (WIDTHxHEIGHT)
SCREENSHOT_INTERVAL	60	Screenshot frequency in minutes
PAGE_LOAD_DELAY	10	Wait time in seconds before capturing
TZ	America/Toronto	Timezone for timestamps
IMAGE_FORMAT	jpeg	Output format: jpeg or webp
IMAGE_QUALITY	80	Compression quality (1-100)

Example resolutions for older iPads:

• iPad 1/2: 1024x768
• iPad 3/4: 2048x1536
• iPad Mini 1: 1024x768

Example intervals:

• 5 - Every 5 minutes
• 30 - Every 30 minutes
• 60 - Every hour (default)
• 1440 - Once daily

How It Works

1. Takes a screenshot of the target URL at specified intervals using headless Chromium
2. Converts to optimized JPEG (or WebP) for minimal file size
3. Serves the screenshot at /latest.jpg with an auto-refreshing HTML viewer
4. Managed by Supervisord: nginx + cron + initial screenshot on startup

Manual Docker Build

# Build the image
docker build -t screenshot-server .

# Run the container
docker run -d \
  -p 8080:80 \
  -e TARGET_URL="http://192.168.0.121:8180/" \
  -e RESOLUTION="1024x768" \
  -e SCREENSHOT_INTERVAL="60" \
  -e PAGE_LOAD_DELAY="10" \
  -e TZ="America/Toronto" \
  screenshot-server

CI/CD with GitHub Actions

On every push to main:

• Builds multi-architecture images (amd64 and arm64)
• Publishes to Docker Hub as flucko/screenshot-server:latest
• Semver tags (v1.2.3) also create versioned images

Breaking Changes

v2.0

• Single image: The separate Alpine and Ubuntu image variants have been removed. There is now a single Alpine-based image (latest). If you were using docker-compose.alpine.yml, switch to docker-compose.yml.
• JPEG output: Screenshots are now saved as latest.jpg instead of latest.png by default. Set IMAGE_FORMAT=webp for WebP output. The index.html viewer handles this automatically.
• Chrome persistence removed: The KEEP_CHROME_OPEN, CHROME_MAX_MEMORY_MB, and CHROME_RESTART_HOURS environment variables are no longer supported. Chrome starts fresh for each screenshot.

Troubleshooting

1. Page not fully loaded: Increase PAGE_LOAD_DELAY value
2. Wrong timezone: Set TZ environment variable in docker-compose.yml
3. View logs: docker-compose logs -f
4. Check cron: docker exec <container-id> crontab -l
5. Check processes: docker exec <container-id> supervisorctl status