# Background Removal Tool

A Rust-based background removal tool using ONNX models (BiRefNet) with GPU support.

## Features

- Download images from URLs
- Automatic ONNX model download and caching
- Background removal using BiRefNet-general-lite model
- Side-by-side comparison display (original vs processed)
- Checkered background visualization for transparency
- CLI with flexible options

## Building

### With Nix (Recommended)

```bash
# Enter the development environment
nix develop

# Build the project
cargo build --release
```

### Without Nix

If you don't use Nix, you'll need to ensure you have the following system dependencies:
- Rust toolchain
- OpenSSL development libraries (`libssl-dev` on Ubuntu/Debian)
- pkg-config
- X11 libraries (for window display)
- Vulkan loader

## Usage

Basic usage:

```bash
# Download and process an image
cargo run -- https://example.com/image.jpg

# Use custom model
cargo run -- https://example.com/image.jpg --model-path ./custom_model.onnx

# Offline mode (use only cached model)
cargo run -- https://example.com/image.jpg --offline
```

## How It Works

1. **Download**: Fetches the image from the provided URL
2. **Model Loading**: Auto-downloads BiRefNet model (cached in `~/.cache/remove_background/models/`)
3. **Preprocessing**: Resizes image to 1024x1024, normalizes pixels, converts to CHW format
4. **Inference**: Runs ONNX model to generate foreground mask
5. **Postprocessing**: Applies mask to original image, creates RGBA output
6. **Display**: Shows side-by-side comparison with checkered background

## Project Structure

```
src/
├── main.rs           - CLI interface and orchestration
├── model.rs          - Model download and ONNX session management
├── preprocessing.rs  - Image preprocessing (resize, normalize, CHW conversion)
└── postprocessing.rs - Mask application and side-by-side display creation
```

## Dependencies

- **ort**: ONNX Runtime Rust bindings
- **ndarray**: N-dimensional array operations
- **image**: Image loading and manipulation
- **reqwest**: HTTP client for downloads
- **show-image**: Cross-platform window display
- **clap**: Command-line argument parsing
- **sha2**: Hash verification

## Future Enhancements

- [ ] CUDA execution provider support (GPU acceleration)
- [ ] Batch processing support
- [ ] Additional model options (U2-Net, ISNet, etc.)
- [ ] Save output to file
- [ ] Local file input support
- [ ] Progress bars for downloads
- [ ] WebAssembly support

## Controls

- **ESC**: Close the window and exit

## Model Information

Default model: **BiRefNet-general-lite**
- Size: ~50MB
- Input: 1024x1024 RGB
- Output: 1024x1024 mask
- Source: https://huggingface.co/ZhengPeng7/BiRefNet

## License

See LICENSE file for details.