PrintCalC

A local-first PDF print pricing tool that analyzes ink coverage per page and calculates fair, shop-ready costs — no cloud, no accounts, no data leaving your machine.

Download for macOS / Windows →

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What it does

Print shops typically charge flat rates that disadvantage customers with lightly-inked pages. PrintCalC solves this by measuring actual ink coverage and pricing each page against configurable cost slabs — the same way a fair shop would.

• Renders every PDF page via PyMuPDF and classifies each pixel as white, color, or black/grey using RGB threshold + CMY chroma analysis
• Supports Color and B/W printer modes with separate pricing profiles for single-sided and duplex jobs
• Blank pages (100% white) are always free
• Border-ignore margin strips header/footer noise before measurement
• Fast (200 DPI) and Accurate (300 DPI) analysis modes
• All processing is local — the PDF never leaves the device

Tech stack

Layer	Choice
UI	Streamlit
PDF rendering	PyMuPDF (fitz)
Pixel analysis	NumPy
Data / display	Pandas
Packaging	PyInstaller (onedir)
CI/CD	GitHub Actions (build + release)

How it works

1. PDF → pixels — each page is rasterized at the chosen DPI using PyMuPDF's get_pixmap, then loaded into a NumPy array
2. Pixel classification — white pixels are identified by RGB threshold; among the rest, per-pixel CMY chroma (max(C,M,Y) - min(C,M,Y)) determines color vs grey
3. Slab lookup — the resulting coverage percentages are matched against user-editable price slabs (stored in Streamlit session state, with overlap/gap validation)
4. Output — a per-page breakdown table plus total pages, sheets, price, and processing time

Running locally

python -m venv .venv && source .venv/bin/activate
pip install -r requirements.txt
streamlit run app.py

Project structure

app.py          # entire application — analysis, pricing logic, Streamlit UI
launcher.py     # PyInstaller entry point: spawns Streamlit, opens browser
requirements.txt
.github/
  workflows/
    build.yml   # builds Windows + macOS ZIPs on push to main
    release.yml # attaches ZIPs to GitHub Releases on tag push

Key design decisions

• Single-file app — all logic lives in app.py to keep the packaged artifact simple and auditable
• No backend — Streamlit's session state is the only persistence; there's nothing to deploy or secure
• Configurable slabs — shop owners can adjust pricing tiers directly in the UI without touching code; slabs are validated for overlaps and gaps before use
• Launcher pattern — launcher.py wraps Streamlit in a subprocess so PyInstaller can produce a native executable that behaves like a desktop app