CLAUDE.md

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

Project Overview

Chrome is a high-performance C++17 port of negfix8, a tool for processing scanned color negative film. It inverts and color-corrects 16-bit linear Rec.709 TIFF images from film scanners.

Build Commands

# Configure and build
cmake -B build/ -S .
cd build && make

# The executable is built at build/chrome

Dependencies: OpenCV (core, imgproc, imgcodecs), OpenMP (optional, for parallelization)

Testing

Manual testing only. Compare output against reference files in test_data/:

test_data/test_input.tiff - Sample input scan
test_data/test_expected.tiff - Reference output from original negfix8
test_data/current_output.tiff - Current implementation output

./build/chrome -i test_data/test_input.tiff -o test_data/current_output.tiff
# Then visually compare or diff against test_data/test_expected.tiff

Usage

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

Flags:
  -g <val>    Set gamma (default 2.15)
  -cs         Enable contrast stretching
  -sat        Enable saturation boost (+20%)
  -m          Mirror image horizontally
  -r <N>      Binning (scale down by 1/N)
  -c <file>   Create profile and save to file (exits after)
  -u <file>   Use existing profile

Architecture

Single-file implementation in main.cpp with this pipeline:

Settings/Profile structs - CLI options and image analysis data
Image analysis (analyzeImage) - Finds min/max per channel after shave+blur preprocessing
Profile save/load - Stores derived gamma corrections and offset values
LUT generation (generateLUTs) - Creates 65536-entry lookup tables for each channel using OpenMP
Pixel processing - Applies LUTs in parallel via OpenMP
Post-processing - Optional saturation boost, contrast stretch, mirror
Output - Writes LZW-compressed TIFF

The core algorithm inverts negative film by dividing film base values by pixel values, applies per-channel gamma correction to neutralize orange mask, then applies global gamma.

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