overflowy/make-look-scanned

Source: https://github.com/overflowy/make-look-scanned

make-look-scanned

A CLI that takes a PDF and degrades it to look like a physical scan of a printout — skew, grayscale, warm paper tone, scanner grain, defocus, edge shadow, and JPEG compression artifacts. Also runs client-side in the browser via WASM.

Each page is rasterized to an image, run through the effect pipeline, and reassembled into a new image-only PDF (the original selectable text is gone — faithful to a basic scanner).

Build

Requires Go and a C toolchain (go-fitz links MuPDF via cgo, so the binary is self-contained — nothing to install at runtime).

go build -o make-look-scanned .

Usage

make-look-scanned [flags] input.pdf

Flags may appear before or after the input filename.

make-look-scanned in.pdf                 # -> in.scanned.pdf
make-look-scanned in.pdf -o out.pdf
make-look-scanned in.pdf --noise 0.4 --skew 2.5 --jpeg-quality 30

Flags

Each numeric knob disables its effect at 0.

Determinism

Output is deterministic by default: the seed is derived from the input PDF’s content, so the same file always produces the same scan. Pass --seed N for a different (but reproducible) look. Same input + seed yields a byte-identical PDF.

Presets

Define reusable bundles in $XDG_CONFIG_HOME/make-look-scanned/config.toml (falls back to ~/.make-look-scanned/config.toml when XDG_CONFIG_HOME is unset). Keys mirror the flag names with underscores:

[presets.medium]
skew = 1.5
paper_tone = 0.6
noise = 0.2
blur = 0.6
edge_shadow = 0.3
jpeg_quality = 45

make-look-scanned --preset medium in.pdf

Precedence: built-in defaults → selected preset → explicit CLI flags (flags always win).

Browser (WebAssembly)

The effect pipeline also runs in the browser. go-fitz/MuPDF can’t compile to wasm, so the browser uses PDF.js to rasterize pages and hands the pixels to the same Go effects + assembly code compiled to wasm.

Dev (needs network for the PDF.js CDN):

./web/build.sh                       # builds web/main.wasm + wasm_exec.js
(cd web && python3 -m http.server 8080)   # then open http://localhost:8080

Single self-contained file (works offline, nothing to serve):

task build:web                       # writes dist/make-look-scanned.html (~8 MB)

dist/make-look-scanned.html inlines the wasm, Go’s runtime glue, and PDF.js (library + worker) as base64 — open it directly in a browser. Output is visually equivalent to the CLI but not byte-identical, since PDF.js and MuPDF rasterize differently.

License

AGPL-3.0. The CLI statically links MuPDF (via go-fitz), which is AGPL-3.0, so the combined binary is AGPL-3.0 — distributing it requires offering the corresponding source. The browser build does not include MuPDF (it uses PDF.js, Apache-2.0).