# CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

## Project

C++ desktop app converting digitized analog film negatives (35mm, 120mm) to digital positives. Supports JPG/PNG and RAW input (CR2/NEF/ARW/DNG), outputs PNG/JPG with inversion, C41/B&W correction, auto-crop, and batch processing. Cross-platform: Windows/Linux/macOS.

## Tech Stack

- **Language:** C++20
- **Image processing:** OpenCV 4.10+ and LibRaw 0.21+ (RAW demosaicing)
- **GUI:** Qt 6.8 LTS (LGPLv3)
- **Build:** CMake 3.20+, vcpkg (Windows), Ninja
- **CLI:** Optional batch mode without GUI

## Build Commands

```bash
# Linux (Ubuntu/Debian)
sudo apt install libopencv-dev libqt6widgets6 libraw-dev cmake ninja-build
cmake -B build -G Ninja -DCMAKE_BUILD_TYPE=Release
cmake --build build

# Windows (vcpkg)
vcpkg install opencv[contrib] libraw qt6-base:x64-windows
cmake -B build -G Ninja -DCMAKE_TOOLCHAIN_FILE=vcpkg.cmake
cmake --build build

# macOS (Homebrew)
brew install opencv libraw qt@6 cmake ninja
cmake -B build -G Ninja
cmake --build build
```

## Architecture

Processing pipeline:

```
Input → Loader → Preprocess → Detect → Invert → Color Correction → Post-Process → Output
```

**Core data structure:**
```cpp
struct ImageData {
    cv::Mat rgb;      // Demosaiced 16-bit
    std::string make; // "Canon", "Nikon"
    float exposure;   // WB/EXIF data
};
```

**Pipeline stages:**
1. **Loader** (`src/converter/rawloader`): LibRaw for RAW→RGB16, OpenCV for JPG/PNG
2. **Preprocess**: RAW→RGB16 conversion, deskew
3. **Detect** (`src/converter/negative`): Negative vs. positive via histogram analysis and orange color masking
4. **Invert**: `cv::bitwise_not()` + film-specific color matrix
5. **Color**: C41 orange cast removal, auto white balance from EXIF
6. **Post** (`src/converter/crop`): Levels, sharpening, dust removal, auto frame detection
7. **Output**: 16-bit TIFF and 8-bit PNG

Error handling uses `std::expected<ImageData, Error>` throughout.

## Coding Standards

- Always call `LibRaw::recycle()` after use
- Qt file dialogs: `QFileDialog::getOpenFileNames("RAW (*.cr2 *.nef *.dng)")`
- Tests use RAW golden files with pixel diff tolerance <1%
- Do not exceed 4GB in-memory RAW data
- Do not use lossy demosaicing (LibRaw default is lossless)
- Always log RAW metadata

## Sample Images

The `import/` directory contains example RAW files for manual testing and development:

| File | Format | Description |
|------|--------|-------------|
| `import/DSC09246.ARW` | Sony ARW | Example negative for conversion testing |
| `import/unbenannt.ARW` | Sony ARW | Example negative for conversion testing |

Use these files to test the full pipeline end-to-end without needing external test data.

## License Compliance

README.md must include:
- Qt LGPLv3 attribution and source download link: https://www.qt.io/download-open-source
- Instructions for re-linking Qt DLLs
- LibRaw CDDL attribution: https://www.libraw.org