pdf-look-scanned

name

pdf-look-scanned

description

Make PDF documents look like they were scanned on a physical scanner. Applies realistic effects: grayscale conversion, Gaussian noise, slight rotation, blur, edge shadows, and random offset. Optionally extract real handwritten signatures from a source PDF (or user-provided images) and replace digital signatures on specific pages. Use when the user asks to: make a PDF look scanned, give a PDF a scanned appearance, replace digital signatures with real/handwritten ones, fake a scan, add scan effects to a document, or make a document look printed and scanned.

PDF Look Scanned

Make PDFs look like physical scans with optional signature replacement.

Dependencies

pip3 install pillow pdf2image img2pdf numpy

Also requires poppler (provides pdftoppm):

• macOS: brew install poppler
• Ubuntu/Debian: apt install poppler-utils
• Fedora/RHEL: dnf install poppler-utils
• Arch: pacman -S poppler
• Windows: conda install -c conda-forge poppler or download from poppler releases

Quick Start

Run scripts/make_scanned.py for the core functionality. Read the script's --help for all options.

Simple scan effect

python3 scripts/make_scanned.py document.pdf

Adjust scan quality

Lower DPI and quality = grittier, more realistic cheap-scanner look:

python3 scripts/make_scanned.py document.pdf --dpi 150 --quality 75 --noise 7

Higher DPI = cleaner scan, larger file:

python3 scripts/make_scanned.py document.pdf --dpi 300 --quality 92

Signature Replacement

Finding signature coordinates

Before replacing signatures, determine crop and placement coordinates. All coordinates are fractions of page dimensions (0.0-1.0).

1. Convert the source PDF to images and visually inspect to find the signature region
2. Iteratively crop to isolate just the signature ink (no text, no table lines)
3. On the target PDF, find the area to clear (old digital signature) and where to paste

Use this Python snippet to explore coordinates interactively:

from pdf2image import convert_from_path
from PIL import Image

pages = convert_from_path("document.pdf", dpi=200)
page = pages[0]  # 0-indexed
w, h = page.size

# Crop a region and save for inspection
crop = page.crop((int(w*0.5), int(h*0.4), int(w*0.8), int(h*0.6)))
import tempfile, os
crop.save(os.path.join(tempfile.gettempdir(), "crop_test.png"))

Replace one signature

python3 scripts/make_scanned.py contract.pdf \
  --sig-pdf signatures.pdf \
  --sig-page 1 --sig-crop 0.41,0.33,0.62,0.42 \
  --sig-target 25 --sig-clear 0.61,0.41,0.85,0.52 --sig-place 0.62,0.415

Replace multiple different signatures

Each set of --sig-page, --sig-crop, --sig-target, --sig-clear, --sig-place adds one replacement. They are matched positionally:

python3 scripts/make_scanned.py contract.pdf \
  --sig-pdf signatures.pdf \
  --sig-page 1 --sig-crop 0.41,0.33,0.62,0.42 \
  --sig-target 25 --sig-clear 0.61,0.41,0.85,0.52 --sig-place 0.62,0.415 \
  --sig-page 2 --sig-crop 0.40,0.335,0.62,0.39 \
  --sig-target 27 --sig-clear 0.61,0.635,0.85,0.72 --sig-place 0.60,0.655

Signature parameters

Parameter	Description
--sig-pdf	Source PDF containing real signatures
--sig-page N	Page number in source PDF (1-indexed)
--sig-crop L,T,R,B	Crop box to extract signature (fractions)
--sig-target N	Target page to replace signature on (1-indexed)
--sig-clear L,T,R,B	Area to white-out old signature (fractions)
--sig-place X,Y	Top-left position to paste new signature (fractions)
--sig-size F	Signature width as fraction of page width (default: 0.11)
--sig-dpi N	DPI for rendering source signature PDF (default: 350)

Scan effect parameters

Parameter	Default	Effect
--dpi	200	Render resolution. Lower = grittier
--quality	85	JPEG compression. Lower = more artifacts
--noise	5.0	Gaussian noise stddev. Higher = noisier
--blur	0.6	Gaussian blur radius. Higher = softer
--rotation	0.7	Max rotation in degrees
--contrast-min	0.88	Min contrast (lower = more washed out)
--contrast-max	0.95	Max contrast

Workflow for signature replacement

When the user provides a PDF and a separate signature source:

1. Check dependencies are installed (pillow, pdf2image, img2pdf, numpy, poppler)
2. Examine the source signature PDF — convert to images, identify which pages have signatures
3. Extract signatures — iteratively crop to isolate the ink, verify no text bleeds in
4. Examine the target PDF — find pages with digital signatures, note the "Подпись:" or "Signature:" label positions
5. Determine coordinates — clear area must cover old signature without eating into labels; place position should be right after the label
6. Run the script with all parameters
7. Verify output — check signature pages visually, adjust coordinates if needed
8. Check metadata — run exiftool on the output to ensure no software traces remain

Common pitfalls:

• Crop box too tight: signature strokes get clipped on edges
• Clear area too wide: eats into "Подпись:"/"Signature:" labels or surrounding text
• Signature too large/small: adjust --sig-size (0.11 is typical for contracts)
• Source PDF is a phone photo: use higher --sig-dpi (350+) and higher ink threshold