Chrome

A high-performance C++ port of negfix8 for processing scanned color negative film. Inverts and color-corrects 16-bit linear Rec.709 TIFF images from film scanners.

Example

Input (Scanned Negative)		Output (Processed)
	➜ `chrome -cs -sat 50 -exp 1.2` ➜

Performance

Tool	Time	Speedup
negfix8 (original)	18m 8s	1x
Chrome	~10s	~109x

Benchmark: 9098×12160 16-bit TIFF (~332MB) 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

sudo apt install cmake libopencv-dev

macOS (Homebrew)

brew install cmake opencv libomp

Build

cmake -B build -S .
cmake --build build

The executable is built at build/chrome.

Usage

./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

# 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`

# 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 by Chris Hunt
Original negfix algorithm created by JaZ99

License

Licensed under the Apache License, Version 2.0. See LICENSE for details.

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