# PDF Export Functionality

The gallery now includes the ability to export multiple plots to a merged PDF with grid layout.

## Features

- Select up to 4 plots from any gallery page
- Automatic grid layout (1x1, 1x2, 2x2)
- Export to PDF with proper scaling
- Keyboard shortcuts for easy access

## Usage

### Selecting Plots

1. Press **Ctrl+E** to enter selection mode
2. Click on up to 4 plot thumbnails to select them
3. Selected plots will show a checkmark overlay
4. A counter shows how many plots are selected (e.g., "2/4 selected")

### Exporting

1. After selecting plots, click the **📄** export button (appears in floating buttons)
2. The system will show export instructions with:
   - JSON data for the export request
   - Command to run the export script
3. Copy the JSON data and save it as `export_request.json`
4. Run the export command in your terminal

### Keyboard Shortcuts

- **Ctrl+E**: Toggle selection mode
- **Escape**: Clear all selections and exit selection mode

## Export Methods

The system supports two PDF merging methods:

### Method 1: pdfjam (Recommended)
```bash
# Install on Ubuntu/Debian
sudo apt-get install texlive-extra-utils

# Check if available
python export_plots.py --check-deps
```

### Method 2: Python libraries
```bash
# Install Python dependencies
pip install PyPDF2 reportlab

# Check if available
python export_plots.py --check-deps
```

## Export Script Usage

```bash
# Basic usage
python export_plots.py export_request.json

# Specify output file
python export_plots.py export_request.json --output my_plots.pdf

# Check available dependencies
python export_plots.py --check-deps
```

## JSON Request Format

```json
{
  "plots": [
    "/path/to/plot1.pdf",
    "/path/to/plot2.pdf"
  ],
  "layout": {
    "rows": 1,
    "cols": 2
  },
  "output_name": "merged_plots.pdf"
}
```

## Layout Options

- **1 plot**: 1x1 grid
- **2 plots**: 1x2 grid (horizontal)
- **3 plots**: 2x2 grid (one empty slot)
- **4 plots**: 2x2 grid (full)

## Technical Details

The export functionality consists of:

- **Frontend**: JavaScript selection UI and export manager
- **Backend**: Python script for PDF merging
- **CSS**: Styling for selection mode and overlays

The system is designed to work without requiring a web server, using file-based communication between the browser and Python script.