OCRmyPDF チュートリアル：スキャン文書を検索可能な PDF/A ファイルに変換し、サイドカーテキスト抽出とバッチ処理を行う方法

In this tutorial, we build an advanced, self-contained OCRmyPDF workflow. We start by installing the required system and Python dependencies, then create a synthetic image-only PDF for scanning so we can test OCR without relying on external files. From there, we use OCRmyPDF’s real public API to convert scanned documents into searchable PDFs, generate PDF/A outputs, extract sidecar text, validate the results, compare file sizes, tune Tesseract settings, clean noisy scans, handle already-OCRed files, process images with DPI hints, run OCR in memory, and batch-process multiple PDFs. Through this workflow, we understand how OCRmyPDF can serve as a practical document digitization pipeline for archival, search, extraction, and automated processing tasks.

Installing OCRmyPDF System Dependencies

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import io

import os

import re

import sys

import time

import shutil

import logging

import textwrap

import subprocess

from pathlib import Path

INSTALL_JBIG2 = True

def sh(cmd: str, check: bool = True) -> int:

"""Run a shell command, echo it, and show the tail of its output."""

print(f" $ {cmd}")

r = subprocess.run(cmd, shell=True, text=True,

stdout=subprocess.PIPE, stderr=subprocess.STDOUT)

if r.stdout and r.stdout.strip():

for ln in r.stdout.strip().splitlines()[-12:]:

print(" " + ln)

if check and r.returncode != 0:

raise RuntimeError(f"Command failed ({r.returncode}): {cmd}")

return r.returncode

def install_dependencies() -> None:

"""Install OCRmyPDF's system + Python dependencies for Colab/Ubuntu."""

apt_pkgs = (

"tesseract-ocr tesseract-ocr-eng tesseract-ocr-osd "

"tesseract-ocr-deu tesseract-ocr-fra "

"ghostscript unpaper pngquant poppler-utils qpdf"

)

sh("apt-get update -qq", check=False)

sh(f"DEBIAN_FRONTEND=noninteractive apt-get install -y -qq {apt_pkgs}")

sh(f'"{sys.executable}" -m pip install -q --upgrade ocrmypdf img2pdf "pillow<12"')

if INSTALL_JBIG2 and shutil.which("jbig2") is None:

try:

build_pkgs = ("autoconf automake libtool pkg-config "

"libleptonica-dev zlib1g-dev build-essential git")

sh(f"DEBIAN_FRONTEND=noninteractive apt-get install -y -qq {build_pkgs}")

sh("rm -rf /tmp/jbig2enc && "

"git clone -q https://github.com/agl/jbig2enc.git /tmp/jbig2enc")

sh("cd /tmp/jbig2enc && ./autogen.sh >/dev/null 2>&1 && "

"./configure >/dev/null 2>&1 && make -j2 >/dev/null 2>&1 && "

"make install >/dev/null 2>&1 && ldconfig")

print(" jbig2enc:",

"installed" if shutil.which("jbig2") else "built, but binary not on PATH")

except Exception as e:

print(" jbig2enc build skipped (optional):", e)

def ensure_installed() -> None:

have_tools = bool(shutil.which("tesseract") and shutil.which("gs"))

try:

import ocrmypdf

import img2pdf

from PIL import Image

have_py = True

except Exception:

have_py = False

if have_tools and have_py:

print("Dependencies already present — skipping installation.")

else:

print("Installing dependencies (first run can take a few minutes)...")

install_dependencies()

ensure_installed()

We set up the complete OCRmyPDF environment for Google Colab by importing the required standard libraries and defining the installation workflow. We install system tools such as Tesseract, Ghostscript, unpaper, pngquant, poppler, and qpdf, along with Python packages like OCRmyPDF, img2pdf, and Pillow. We also optionally build jbig2enc so that advanced PDF optimization can produce smaller outputs for scanned documents.

Loading OCRmyPDF and Building Synthetic Scans

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def _purge(*prefixes):

for name in [m for m in list(sys.modules)

if any(m == p or m.startswith(p + ".") for p in prefixes)]:

del sys.modules[name]

def _load_ocrmypdf():

_purge("PIL", "ocrmypdf")

import ocrmypdf

return ocrmypdf

try:

ocrmypdf = _load_ocrmypdf()

except ImportError as e:

if "_Ink" in str(e) or "PIL" in str(e):

print("Repairing an incompatible Pillow (reinstalling pillow<12)...")

sh(f'"{sys.executable}" -m pip install -q --force-reinstall "pillow<12"')

try:

ocrmypdf = _load_ocrmypdf()

print("Pillow repaired — continuing without a restart.")

except Exception:

raise RuntimeError(

"Pillow is still incompatible in this session. Use the Colab menu: "

"Runtime > Restart session, then run this cell again."

)

else:

raise

from ocrmypdf.exceptions import (

ExitCode,

PriorOcrFoundError,

EncryptedPdfError,

MissingDependencyError,

TaggedPDFError,

DigitalSignatureError,

DpiError,

InputFileError,

UnsupportedImageFormatError,

)

from ocrmypdf.helpers import check_pdf

from ocrmypdf.pdfa import file_claims_pdfa

import img2pdf

from PIL import Image, ImageDraw, ImageFont, ImageFilter

logging.basicConfig(level=logging.WARNING, format="%(levelname)s: %(message)s")

logging.getLogger("ocrmypdf").setLevel(logging.WARNING)

logging.getLogger("pdfminer").setLevel(logging.ERROR)

logging.getLogger("PIL").setLevel(logging.WARNING)

SAMPLE_TEXT_PAGES = [

"Optical Character Recognition, commonly abbreviated as OCR, is the "

"process of converting images of typed or printed text into machine "

"encoded text. This page was generated as a synthetic scan so that the "

"OCRmyPDF pipeline has something realistic to recognize and search.",

"On 14 March 2026 the archive contained 1,482 pages across 37 folders. "

"Roughly 92 percent of those pages were scanned at 200 to 300 dots per "

"inch. The remaining 8 percent were skewed and required deskewing before "

"any reliable recognition was possible.",

"After OCRmyPDF finishes, the output is a searchable PDF/A file. You can "

"select text, copy it, and run full text search across thousands of "

"documents. The original image resolution is preserved while a hidden "

"text layer is placed accurately underneath the page image.",

]

def _find_font():

for cand in (

"/usr/share/fonts/truetype/dejavu/DejaVuSans.ttf",

"/usr/share/fonts/truetype/liberation/LiberationSans-Regular.ttf",

):

if os.path.exists(cand):

return cand

return None

_FONT_PATH = _find_font()

FONT = ImageFont.truetype(_FONT_PATH, 40) if _FONT_PATH else ImageFont.load_default()

def _add_speckle(img, n=6000, dark=60):

"""Sprinkle light dark specks to imitate scanner noise (motivates --clean)."""

import random

px = img.load()

w, h = img.size

for _ in range(n):

px[random.randint(0, w - 1), random.randint(0, h - 1)] = random.randint(0, dark)

return img

def render_page(text, skew=False):

"""Render one A4 page (1654x2339 px ≈ 200 DPI) of dark text on white."""

W, H = 1654, 2339

img = Image.new("L", (W, H), 255)

draw = ImageDraw.Draw(img)

draw.multiline_text((150, 180), textwrap.fill(text, width=58),

fill=25, font=FONT, spacing=18)

if skew:

img = img.rotate(6, resample=Image.BICUBIC, expand=False, fillcolor=255)

img = img.filter(ImageFilter.GaussianBlur(0.6))

img = _add_speckle(img)

return img

def build_scanned_pdf(pdf_path: Path, pages_text, skew_index=1):

"""Render pages to PNGs and wrap them losslessly into an image-only PDF."""

pngs = []

for i, text in enumerate(pages_text):

img = render_page(text, skew=(i == skew_index))

p = pdf_path.parent / f"_pg_{pdf_path.stem}_{i}.png"

img.save(p, format="PNG", dpi=(200, 200))

pngs.append(str(p))

with open(pdf_path, "wb") as f:

f.write(img2pdf.convert(pngs))

for p in pngs:

os.remove(p)

return pdf_path

def do_ocr(input_file, output_file, **kw):

"""Wrapper around ocrmypdf.ocr() that disables the progress bar and times it."""

kw.setdefault("progress_bar", False)

t0 = time.perf_counter()

rc = ocrmypdf.ocr(input_file, output_file, **kw)

return rc, time.perf_counter() - t0

def tokens(s: str):

return re.findall(r"[a-z0-9]+", s.lower())

def kb(path) -> str:

return f"{Path(path).stat().st_size / 1024:,.1f} KB"

def banner(title: str):

line = "─" * 74

print(f"\n{line}\n {title}\n{line}")

We safely load OCRmyPDF and repair Pillow compatibility issues if they appear in the Colab runtime. We import OCRmyPDF exceptions, PDF validation helpers, img2pdf, and Pillow utilities used throughout the tutorial. We also define the sample document text and helper functions for rendering synthetic scanned pages, adding scanner-like noise, building image-only PDFs, timing OCR runs, tokenizing text, formatting file sizes, and printing section banners.

Running Basic and Advanced PDF/A OCR

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banner("0 · Environment")

print("Python :", sys.version.split()[0])

print("ocrmypdf:", ocrmypdf.__version__)

sh("tesseract --version", check=False)

sh("gs --version", check=False)

sh("tesseract --list-langs", check=False)

print("unpaper :", shutil.which("unpaper"))

print("pngquant:", shutil.which("pngquant"))

print("jbig2 :", shutil.which("jbig2"), "(optional encoder)")

WORK = Path("/content/ocrmypdf_demo")

try:

WORK.mkdir(parents=True, exist_ok=True)

except Exception:

WORK = Path.cwd() / "ocrmypdf_demo"

WORK.mkdir(parents=True, exist_ok=True)

print("Workdir :", WORK)

banner("1 · Build a synthetic image-only 'scanned' PDF")

input_pdf = WORK / "scanned_input.pdf"

build_scanned_pdf(input_pdf, SAMPLE_TEXT_PAGES, skew_index=1)

print(f"Created {input_pdf.name} ({kb(input_pdf)}, 3 pages; page 2 is skewed + speckled)")

print("This PDF has NO text layer yet — selecting/searching it returns nothing.")

banner("2 · Basic OCR (deskew + auto-rotate)")

out_basic = WORK / "out_basic.pdf"

rc, dt = do_ocr(

input_pdf, out_basic,

language=["eng"],

deskew=True,

rotate_pages=True,

)

print(f"Exit code: {rc.name} ({int(rc)}) in {dt:.1f}s -> {out_basic.name} ({kb(out_basic)})")

banner("3 · Advanced OCR (PDF/A-2, --optimize 3, sidecar, metadata)")

out_adv = WORK / "out_advanced.pdf"

sidecar = WORK / "ocr_text.txt"

rc, dt = do_ocr(

input_pdf, out_adv,

language=["eng"],

deskew=True,

rotate_pages=True,

optimize=3,

jpg_quality=80,

png_quality=80,

output_type="pdfa-2",

sidecar=sidecar,

title="OCRmyPDF Colab Tutorial",

author="Tutorial",

subject="Demonstration of OCRmyPDF",

keywords="ocr, pdf, tesseract, ocrmypdf",

)

print(f"Exit code: {rc.name} ({int(rc)}) in {dt:.1f}s -> {out_adv.name} ({kb(out_adv)})")

sh(f'pdfinfo "{out_adv}" | grep -E "Title|Author|Subject|Keywords|Pages"', check=False)

We begin the main tutorial by printing the OCR environment details, including Python, OCRmyPDF, Tesseract, Ghostscript, installed languages, and optional optimization tools. We create a working directory and generate a synthetic scanned PDF that has no searchable text layer. We then run both a basic OCR workflow and an advanced OCR workflow with PDF/A output, image optimization, sidecar text generation, and document metadata.

Validating Searchability and OCR Word-Recall

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banner("4 · Prove searchability + measure OCR word-recall")

ocr_text = sidecar.read_text(errors="ignore")

print("Sidecar text (first 300 chars):\n" + ocr_text[:300].strip())

embedded = WORK / "embedded_text.txt"

sh(f'pdftotext "{out_adv}" "{embedded}"', check=False)

print(f"\npdftotext extracted {len(embedded.read_text(errors='ignore').split())} "

f"words from the OUTPUT PDF (the input had 0).")

src = tokens(" ".join(SAMPLE_TEXT_PAGES))

found = set(tokens(ocr_text))

recall = sum(1 for w in src if w in found) / max(1, len(src))

print(f"OCR word-recall vs. source: {recall * 100:.1f}% ({len(src)} source words)")

banner("5 · Validate output + size comparison")

print("check_pdf (valid PDF structure):", check_pdf(out_adv))

print("file_claims_pdfa (PDF/A marker):", file_claims_pdfa(out_adv))

print(f"input : {kb(input_pdf)}")

print(f"basic : {kb(out_basic)}")

print(f"advanced : {kb(out_adv)} (PDF/A-2 + image optimisation)")

banner("6 · Modes & exceptions: skip-text / redo-ocr / force-ocr")

try:

do_ocr(out_adv, WORK / "should_fail.pdf", language=["eng"])

print("Unexpected: no exception was raised.")

except PriorOcrFoundError as e:

print(f"Caught PriorOcrFoundError (exit code {e.exit_code}): the PDF already "

f"has text. Choose a mode to override:")

rc, _ = do_ocr(out_adv, WORK / "out_skiptext.pdf", language=["eng"], skip_text=True)

print(f" --skip-text -> {rc.name}")

rc, _ = do_ocr(out_adv, WORK / "out_redo.pdf", language=["eng"], redo_ocr=True)

print(f" --redo-ocr -> {rc.name}")

rc, _ = do_ocr(out_adv, WORK / "out_force.pdf", language=["eng"], force_ocr=True)

print(f" --force-ocr -> {rc.name}")

We prove that OCR has made the scanned PDF searchable by reading the sidecar text and extracting embedded text from the output PDF using pdftotext. We compare the recovered OCR text against the known source text to calculate a simple word-recall score. We then validate the PDF structure, check the PDF/A marker, compare file sizes, and demonstrate how OCRmyPDF handles files that already contain OCR text using skip-text, redo-OCR, and force-OCR modes.

Tuning, Cleaning, and In-Memory OCR

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banner("7 · Tesseract engine tuning (--oem / --psm)")

rc, dt = do_ocr(

input_pdf, WORK / "out_tuned.pdf",

language=["eng"],

tesseract_oem=1,

tesseract_pagesegmode=3,

output_type="pdf",

)

print(f"Tuned run -> {rc.name} in {dt:.1f}s")

banner("8 · Image cleaning with unpaper (--clean / --clean-final)")

try:

rc, dt = do_ocr(

input_pdf, WORK / "out_cleaned.pdf",

language=["eng"], deskew=True,

clean=True, clean_final=True, output_type="pdf",

)

print(f"Cleaned run -> {rc.name} in {dt:.1f}s")

except Exception as e:

print("Cleaning step skipped (unpaper issue):", type(e).__name__, e)

banner("9 · Auto-orientation (OSD) on a 90°-rotated page (--rotate-pages)")

try:

rot_png = WORK / "_rot.png"

render_page(SAMPLE_TEXT_PAGES[0]).rotate(90, expand=True, fillcolor=255) \

.save(rot_png, format="PNG", dpi=(200, 200))

rot_pdf = WORK / "rotated_input.pdf"

with open(rot_pdf, "wb") as f:

f.write(img2pdf.convert([str(rot_png)]))

os.remove(rot_png)

rot_side = WORK / "rotated_text.txt"

rc, dt = do_ocr(

rot_pdf, WORK / "out_rotated_fixed.pdf",

language=["eng"], rotate_pages=True, sidecar=rot_side, output_type="pdf",

)

n = len(rot_side.read_text(errors="ignore").split())

print(f"OSD corrected the page; recovered {n} words -> {rc.name} in {dt:.1f}s")

except Exception as e:

print("Auto-orientation demo skipped:", type(e).__name__, e)

banner("10 · OCR a single image (image_dpi hint)")

single_png = WORK / "single_scan.png"

render_page(SAMPLE_TEXT_PAGES[2]).save(single_png, format="PNG")

rc, dt = do_ocr(

single_png, WORK / "out_from_image.pdf",

language=["eng"],

image_dpi=200,

output_type="pdf",

)

print(f"Image -> searchable PDF: {rc.name} in {dt:.1f}s")

banner("11 · In-memory OCR with BytesIO streams")

in_io = io.BytesIO(input_pdf.read_bytes())

out_io = io.BytesIO()

ocrmypdf.ocr(in_io, out_io, language=["eng"], output_type="pdf", progress_bar=False)

out_bytes = out_io.getvalue()

(WORK / "out_in_memory.pdf").write_bytes(out_bytes)

print(f"OCR'd entirely in RAM -> {len(out_bytes):,} bytes written to out_in_memory.pdf")

We experiment with Tesseract engine tuning by setting OCR engine mode and page segmentation mode directly through OCRmyPDF. We then use unpaper-based image cleaning to improve noisy scanned pages and optionally embed the cleaned image into the final output. We also test automatic page orientation correction, convert a single image into a searchable PDF using an explicit DPI hint, and run OCR entirely in memory using BytesIO streams.

Batch OCR and the Typed OcrOptions API

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banner("12 · Batch-process a folder of PDFs")

batch_in = WORK / "batch_in"

batch_out = WORK / "batch_out"

batch_in.mkdir(exist_ok=True)

batch_out.mkdir(exist_ok=True)

build_scanned_pdf(batch_in / "invoice_001.pdf",

[SAMPLE_TEXT_PAGES[0], SAMPLE_TEXT_PAGES[1]], skew_index=1)

build_scanned_pdf(batch_in / "memo_002.pdf",

[SAMPLE_TEXT_PAGES[2]], skew_index=-1)

print(f"{'file':<20}{'result':<14}{'time':<8}size")

for src_pdf in sorted(batch_in.glob("*.pdf")):

dst = batch_out / src_pdf.name

try:

rc, dt = do_ocr(src_pdf, dst, language=["eng"],

deskew=True, output_type="pdfa")

print(f"{src_pdf.name:<20}{rc.name:<14}{dt:<8.1f}{kb(dst)}")

except Exception as e:

print(f"{src_pdf.name:<20}{type(e).__name__:<14}{'-':<8}-")

banner("13 · New-style typed OcrOptions API (v17+)")

try:

from ocrmypdf._options import OcrOptions

opts = OcrOptions(

input_file=str(input_pdf),

output_file=str(WORK / "out_options.pdf"),

languages=["eng"],

deskew=True,

rotate_pages=True,

output_type="pdfa",

progress_bar=False,

)

rc = ocrmypdf.ocr(opts)

print(f"OcrOptions run -> {rc.name} ({int(rc)})")

except Exception as e:

print("OcrOptions API not available in this version:", type(e).__name__, e)

banner("14 · Results")

produced = sorted(p for p in WORK.glob("*.pdf"))

for p in produced:

print(f" {p.name:<26}{kb(p)}")

for p in sorted(batch_out.glob("*.pdf")):

print(f" batch_out/{p.name:<16}{kb(p)}")

print(f"\nAll files are in: {WORK}")

try:

from google.colab import files

for p in [out_adv, out_basic, sidecar, embedded]:

if Path(p).exists():

files.download(str(p))

except Exception as e:

print("(Colab download unavailable — open the files from the panel instead.)", e)

print("\nDone. image")

We scale the workflow from a single file to folder-level batch processing by creating multiple synthetic input PDFs and OCRing each one into an output directory. We then try the newer typed OcrOptions API, which allows us to pass validated OCR settings as a structured options object. Also, we list all generated PDF outputs, including batch results, provide the working directory path, and download key files.

Conclusion

In conclusion, we have a complete OCRmyPDF pipeline that goes far beyond basic scanned-PDF conversion. We created realistic scanned inputs, applied OCR with deskewing and rotation correction, generated optimized PDF/A files, verified embedded text, measured OCR recall, validated PDF structure, and experimented with multiple processing modes, including skip-text, redo-OCR, and force-OCR. We also explored practical production features, including image cleaning, Tesseract engine tuning, in-memory processing, and folder-level batch OCR.

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The post OCRmyPDF Tutorial: Convert Scanned Documents into Searchable PDF/A Files with Sidecar Text Extraction and Batch Processing appeared first on MarkTechPost.