# Chrome

A high-performance C++ port of [negfix8](https://github.com/chrishunt/negfix8) for processing scanned color negative film. Inverts and color-corrects 16-bit linear Rec.709 TIFF images from film scanners.

## Example

<table>
<tr>
<td align="center"><strong>Input (Scanned Negative)</strong></td>
<td align="center"></td>
<td align="center"><strong>Output (Processed)</strong></td>
</tr>
<tr>
<td><img src="test_data/test_input.jpeg" width="400" alt="Scanned negative"></td>
<td align="center">➜<br><code>chrome -cs -sat 50 -exp 1.2</code><br>➜</td>
<td><img src="test_data/current_output_adj.jpeg" width="400" alt="Processed output"></td>
</tr>
</table>

## Performance

### Chrome vs negfix8

| Image | Tool | Flags | Time | Speedup |
|-------|------|-------|------|---------|
| Large (9098×12160, 633MB) | negfix8 | — | 18m 8s | 1x |
| Large (9098×12160, 633MB) | **Chrome** | — | **1.26s** | **~865x** |
| Small (4272×6272, 153MB) | negfix8 | — | 22.0s | 1x |
| Small (4272×6272, 153MB) | **Chrome** | — | **0.41s** | **~54x** |

### Chrome Detailed Benchmarks

#### Large Image (test_input.tiff — 9098×12160, 633MB)

| Flags | Time |
|-------|------|
| *(baseline)* | 1.26s |
| `-cs` | 1.38s |
| `-sat 50` | 1.38s |
| `-exp 1.2` | 1.39s |
| `-cs -sat 50 -exp 1.2` | 1.45s |

#### Small Image (test_input_small.tiff — 4272×6272, 153MB)

| Flags | Time |
|-------|------|
| *(baseline)* | 0.41s |
| `-cs` | 0.36s |
| `-sat 50` | 0.35s |
| `-exp 1.2` | 0.35s |
| `-cs -sat 50 -exp 1.2` | 0.36s |

*Benchmarks run on AMD Ryzen 9 7950X3D (32 threads, 64GB RAM)*

## Features

- LUT-based pixel processing with OpenMP parallelization
- Per-channel gamma correction to neutralize orange mask
- Profile save/load for consistent batch processing
- Optional saturation boost, contrast stretching, exposure adjustment, mirror

## Building

### Dependencies

- CMake 3.x+
- OpenCV (core, imgproc, imgcodecs)
- OpenMP (optional, for parallelization)

#### Ubuntu/Debian

```bash
sudo apt install cmake libopencv-dev
```

#### macOS (Homebrew)

```bash
brew install cmake opencv libomp
```

### Build

```bash
cmake -B build -S .
cmake --build build
```

The executable is built at `build/chrome`.

## Usage

```bash
./build/chrome -i input.tif [-o output.tif] [flags]
```

### Flags

| Flag | Description |
|------|-------------|
| `-g <val>` | Set gamma (default 2.15) |
| `-cs` | Enable contrast stretching |
| `-exp <N>` | Exposure adjustment in stops (-10 to +10) |
| `-sat [N]` | Saturation boost, N=0-100 (default 20 if no value) |
| `-m` | Mirror image horizontally |
| `-r <N>` | Binning/downscale by factor N |
| `-c <file>` | Create profile from image and save (exits after) |
| `-u <file>` | Use existing profile for processing |

### Examples

```bash
# Basic conversion
./build/chrome -i scan.tiff -o output.tiff

# With adjustments (contrast stretch, 50% saturation boost, +1.2 stops exposure)
./build/chrome -i scan.tiff -o output.tiff -cs -sat 50 -exp 1.2

# Create a profile for batch processing
./build/chrome -i scan.tiff -c myfilm.profile

# Apply saved profile to multiple images
./build/chrome -i scan2.tiff -o output2.tiff -u myfilm.profile
```

## Testing

Test files are located in `test_data/`:

| File | Description |
|------|-------------|
| `test_input.tiff` | Sample 16-bit scanned negative |
| `test_expected.tiff` | Reference output from original negfix8 |
| `current_output.tiff` | Chrome output (default settings) |
| `current_output_adj.tiff` | Chrome output with `-cs -sat 50 -exp 1.2` |

```bash
# Basic conversion
./build/chrome -i test_data/test_input.tiff -o test_data/current_output.tiff

# With adjustments (as shown in example above)
./build/chrome -i test_data/test_input.tiff -o test_data/current_output_adj.tiff -cs -sat 50 -exp 1.2
```

## Credits

- Original [negfix8](https://github.com/chrishunt/negfix8) by Chris Hunt
- Original negfix algorithm created by JaZ99

## License

Copyright 2025 DWS (Dubey Web Services, DWS LLC)

Licensed under the Apache License, Version 2.0. See [LICENSE](LICENSE) for details.