DMGs

A simple CLI tool to create professional DMG installers for macOS applications.

Features

• Creates styled DMG files with custom background images
• Automatically extracts app name from bundle Info.plist
• Automatically sizes DMG window to match background image dimensions
• Positions app icon and Applications folder symlink automatically based on image size
• Sets custom DMG icon by compositing app icon onto drive icon
• Code signing support with identity validation
• Compresses final DMG for distribution
• Markdown to HTML or Slack mrkdwn conversion

Installation

Build from source:

swift build -c release

Install to /usr/local/bin:

# Copy the binary
cp .build/release/dmgs /usr/local/bin/

# Or create a symlink (recommended for development)
ln -s $(pwd)/.build/release/dmgs /usr/local/bin/dmgs

Usage

Create a DMG (default command)

dmgs <app-path> <background-path> [options]
# or explicitly
dmgs create <app-path> <background-path> [options]

List available signing identities

dmgs identities

Convert Markdown to HTML or Slack mrkdwn

dmgs markdown [<input-path>] [options]

Reads from stdin if no input path is specified.

Arguments

• app-path - Path to the .app bundle
• background-path - Path to the background image for the DMG

The app name is automatically extracted from the bundle's CFBundleDisplayName or CFBundleName in Info.plist.

Create Options

• -o, --output <directory> - Output directory for the DMG (defaults to current directory)
• --icon-size <size> - Icon size in the DMG window (default: 100)
• --sign <identity> - Code signing identity to sign the DMG (e.g., "Developer ID Application")
• -v, --verbose - Show verbose output
• -h, --help - Show help information

Markdown Options

• -o, --output <path> - Output file path (prints to stdout if not specified)
• --slack - Output Slack mrkdwn format instead of HTML

Examples

Basic usage:

dmgs "/path/to/MyApp.app" "/path/to/background.png"

With custom options and code signing:

dmgs "/path/to/MyApp.app" "/path/to/background.png" \
  --output ~/Desktop \
  --icon-size 120 \
  --sign "Developer ID Application: Your Name (TEAM123)" \
  --verbose

List available signing identities:

dmgs identities

Convert Markdown to HTML:

dmgs markdown "/path/to/changelog.md"

Convert Markdown to Slack mrkdwn:

dmgs markdown "/path/to/changelog.md" --slack

Save to file:

dmgs markdown "/path/to/changelog.md" --output "/path/to/output.html"

Pipe from stdin:

cat "/path/to/changelog.md" | dmgs markdown --slack
echo "**bold text**" | dmgs markdown

Testing

Run tests:

swift test

How It Works

1. Configuration

   • Extracts app name from Info.plist (CFBundleDisplayName or CFBundleName)
   • Reads background image dimensions
   • Calculates optimal window bounds (image size + 22px for title bar)
   • Calculates icon positions (app at 1/4 width, Applications at 3/4 width)
   • Validates signing identity if provided

2. DMG Creation

   • Creates a temporary DMG with auto-calculated size
   • Mounts the DMG
   • Copies app bundle to DMG
   • Creates Applications folder symlink
   • Copies background image to .background folder

3. Customization

   • Writes a .DS_Store file directly
   • Sets window bounds to match background image perfectly
   • Positions icons automatically based on image dimensions
   • Applies background image and icon size settings

4. Finalization

   • Unmounts the DMG
   • Converts to compressed, read-only format
   • Sets custom DMG icon (app icon composited onto drive icon)
   • Signs DMG if signing identity provided
   • Verifies signature contains Authority flag
   • Cleans up temporary files

The DMG window is automatically sized to match your background image, and icons are positioned proportionally, ensuring a perfect fit with no manual positioning needed.

License

MIT