BlotTool: A reproducible command-line workflow for western blot densitometry

Western blot densitometry is a routine component of molecular biology workflows but is often performed through interactive image-analysis steps that are incompletely documented. BlotTool is an open-source command-line tool for reproducible, ROI-based western blot densitometry. The workflow separates upstream region-of-interest definition from measurement execution by using explicit CSV files for band and background regions, then outputs raw intensity, background-corrected integrated density, image metadata, saturation flags, and optional ROI overlays. BlotTool is not intended to replace the full FIJI/ImageJ ecosystem or automate band detection. Rather, it provides a lightweight, deterministic measurement workflow for users who need auditable CSV-based outputs and scriptable execution. Validation demonstrates numerical agreement with FIJI/ImageJ for identical ROI measurements, background-corrected output generation on an independent public blot image, and saturation-flag behavior under controlled clipping conditions. BlotTool v1.0.0 defines a stable command-line interface and CSV input/output schema for the documented ROI-based densitometry workflow.