✨ initial commit

.gitignore

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+/pdfsign.venv
+/*.png
+/*.pdf

LICENSE

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+MIT License
+
+Copyright (c) 2025 Yavook.de
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

pdfsign.py

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+#!/usr/bin/env python3
+# make_text_invisible.py
+# Usage: python make_text_invisible.py text.pdf out.pdf
+# Produces a single-page PDF identical visually but with text made invisible (selectable/searchable).
+# Requires: pip install pymupdf
+
+import sys
+import fitz  # pymupdf
+import os
+
+if len(sys.argv) != 4:
+    print("Usage: python make_text_invisible.py text.pdf sig.png out.pdf", file=sys.stderr)
+    sys.exit(2)
+
+in_path, sig_path, out_path = sys.argv[1], sys.argv[2], sys.argv[3]
+
+doc = fitz.open(in_path)
+if doc.page_count < 1:
+    print("Input has no pages", file=sys.stderr)
+    sys.exit(1)
+
+# operate only on first page (single-page input assumed)
+page = doc.load_page(0)
+w, h = page.rect.width, page.rect.height
+
+# create new doc and a blank page with same size
+out = fitz.open()
+newp = out.new_page(width=w, height=h)
+
+# # copy original page's visible content as an image to preserve exact appearance
+# pix = page.get_pixmap(matrix=fitz.Matrix(1, 1), alpha=False)
+# img_bytes = pix.tobytes("png")
+# newp.insert_image(fitz.Rect(0, 0, w, h), stream=img_bytes)
+
+newp.insert_image(newp.rect, filename=sig_path, keep_proportion=False)
+
+# extract text spans (positions, fonts, sizes)
+td = page.get_text("dict")
+
+for block in td.get("blocks", []):
+    for line in block.get("lines", []):
+        for span in line.get("spans", []):
+
+            txt = span.get("text", "")
+            if not txt:
+                continue
+
+            origin = span.get("origin")
+            if origin:
+                x, y = origin[0], origin[1]
+            else:
+                bbox = span.get("bbox", [0,0,0,0])
+                x, y = bbox[0], bbox[3]
+
+            # Use PDF invisible text rendering: render_mode=3 (neither fill nor stroke) is invisible but selectable.
+            try:
+                size = span.get("size", 12)
+                newp.insert_text((x, y), txt, fontsize=size, color=(0, 0, 0, 0), render_mode=3)
+            except Exception:
+                print(f"Failed to insert text: '{txt}'")
+
+out.save(out_path, garbage=4, deflate=True)
+out.close()
+doc.close()

pdfsign.sh

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+#!/bin/bash
+
+#################
+# PREREQUISITES #
+#################
+
+# executables in PATH
+for prereq in "python3" "gs" "pdftk"; do
+    if ! command -v "${prereq}" &> /dev/null; then
+        echo "required executable '${prereq}' not found!"
+        exit 1
+    fi
+done
+
+# python virtual env with PyMuPDF
+VENV_DIR="pdfsign.venv"
+if [ -d "${VENV_DIR}" ]; then
+    # venv exists, activate it
+    source "${VENV_DIR}/bin/activate"
+else
+    for prereq in "venv"; do
+        if ! python3 -c "import ${prereq}" &> /dev/null; then
+            echo "python module '${prereq}' not found!"
+            exit 1
+        fi
+    done
+
+    # create venv and activate
+    python3 -m "venv" "${VENV_DIR}"
+    source "${VENV_DIR}/bin/activate"
+    # install PyMuPDF
+    python3 -m "pip" install PyMuPDF
+fi
+
+
+############
+# CLI ARGS #
+############
+
+if [ $# -lt 2 ]; then
+    echo "Usage: ${0} <input.pdf> <signed.png> [PAGE]"
+    echo
+    echo "Replaces page PAGE with the signed version."
+    echo "If PAGE is not given, the last page is replaced."
+    exit 1
+fi
+
+IN_TEXT_PDF="${1}"
+IN_SCAN_IMG="${2}"
+
+OUT_PDF="${IN_TEXT_PDF%%.*}_pdfsign.pdf"
+
+IN_TEXT_PDF_LEN="$( pdftk "${IN_TEXT_PDF}" dump_data | grep NumberOfPages | awk '{print $2}' )"
+IN_PAGE="${3:-${IN_TEXT_PDF_LEN}}"
+
+RANGES="B1"
+if [ ${IN_PAGE} -gt 1 ]; then
+    RANGES="A1-$(( IN_PAGE - 1 )) ${RANGES}"
+fi
+
+if [ ${IN_PAGE} -lt ${IN_TEXT_PDF_LEN} ]; then
+    RANGES="${RANGES} A$(( IN_PAGE + 1 ))-${IN_TEXT_PDF_LEN}"
+fi
+
+
+################
+# MAIN PROGRAM #
+################
+
+GSFLAGS="-sDEVICE=pdfwrite -dSAFER -dNOPAUSE -dQUIET -dBATCH"
+
+set -e
+
+# extract IN_PAGE (text-only) from IN_TEXT_PDF
+gs ${GSFLAGS} \
+    -dFirstPage="${IN_PAGE}" -dLastPage="${IN_PAGE}" \
+    -dFILTERIMAGE -dFILTERVECTOR -dFILTERTEXT=false \
+    -sOutputFile=".pdfsign_textonly.pdf" \
+    "${IN_TEXT_PDF}"
+
+# use IN_SCAN_IMG as background, layering text from extracted page on top
+python3 ./pdfsign.py \
+    ".pdfsign_textonly.pdf" "${IN_SCAN_IMG}" \
+    ".pdfsign_signed.pdf"
+
+rm ".pdfsign_textonly.pdf"
+
+# replace IN_PAGE in IN_TEXT_PDF layered page
+pdftk A="${IN_TEXT_PDF}" B=".pdfsign_signed.pdf" \
+    cat ${RANGES} \
+    output ".pdfsign_concat.pdf"
+
+rm ".pdfsign_signed.pdf"
+
+# postprocess/compress pdf
+gs ${GSFLAGS} \
+    -sPAPERSIZE=a4 -dFIXEDMEDIA -dPDFFitPage \
+    -dCompatibilityLevel=1.7 -dPDFSETTINGS=/ebook \
+    -sOutputFile="${OUT_PDF}" \
+    ".pdfsign_concat.pdf"
+
+rm ".pdfsign_concat.pdf"