OCR Integration for Scanned Documents¶

Optical Character Recognition (OCR) allows you to extract text from scanned documents where the text isn't embedded in the PDF. This tutorial demonstrates how to work with scanned documents.

In [1]:

#%pip install "natural-pdf[all]"

#%pip install "natural-pdf[all]"

In [2]:

from natural_pdf import PDF

# Load a PDF
pdf = PDF("https://github.com/jsoma/natural-pdf/raw/refs/heads/main/pdfs/needs-ocr.pdf")
page = pdf.pages[0]

# Try extracting text without OCR
text_without_ocr = page.extract_text()
f"Without OCR: {len(text_without_ocr)} characters extracted"

from natural_pdf import PDF # Load a PDF pdf = PDF("https://github.com/jsoma/natural-pdf/raw/refs/heads/main/pdfs/needs-ocr.pdf") page = pdf.pages[0] # Try extracting text without OCR text_without_ocr = page.extract_text() f"Without OCR: {len(text_without_ocr)} characters extracted"

CropBox missing from /Page, defaulting to MediaBox

Out[2]:

'Without OCR: 0 characters extracted'

Applying OCR and Finding Elements¶

The core method is page.apply_ocr(). This runs the OCR process and adds TextElement objects to the page. You can specify the engine and languages.

Note: Re-applying OCR to the same page or region will automatically remove any previously generated OCR elements for that area before adding the new ones.

In [3]:

# Apply OCR using the default engine (EasyOCR) for English
page.apply_ocr(languages=['en'])

# Select all text pieces found by OCR
text_elements = page.find_all('text[source=ocr]')
print(f"Found {len(text_elements)} text elements using default OCR")

# Visualize the elements
text_elements.show()

# Apply OCR using the default engine (EasyOCR) for English page.apply_ocr(languages=['en']) # Select all text pieces found by OCR text_elements = page.find_all('text[source=ocr]') print(f"Found {len(text_elements)} text elements using default OCR") # Visualize the elements text_elements.show()

Using CPU. Note: This module is much faster with a GPU.

/Users/soma/Development/natural-pdf/.venv/lib/python3.11/site-packages/torch/utils/data/dataloader.py:683: UserWarning: 'pin_memory' argument is set as true but not supported on MPS now, then device pinned memory won't be used.
  warnings.warn(warn_msg)

Found 44 text elements using default OCR

Out[3]:

In [4]:

# Apply OCR using PaddleOCR for English and Chinese
page.apply_ocr(engine='paddle', languages=['en', 'ch_sim'])

# Apply OCR using SuryaOCR for English and German
page.apply_ocr(engine='surya', languages=['en', 'de'])

text_with_ocr = page.extract_text()
print(f"\nExtracted text after OCR:\n{text_with_ocr[:150]}...")

# Apply OCR using PaddleOCR for English and Chinese page.apply_ocr(engine='paddle', languages=['en', 'ch_sim']) # Apply OCR using SuryaOCR for English and German page.apply_ocr(engine='surya', languages=['en', 'de']) text_with_ocr = page.extract_text() print(f"\nExtracted text after OCR:\n{text_with_ocr[:150]}...")

Extracted text after OCR:
...

Advanced OCR Configuration¶

For more control, import and use the specific Options class for your chosen engine within the apply_ocr call.

In [5]:

from natural_pdf.ocr import PaddleOCROptions, EasyOCROptions, SuryaOCROptions

# Re-apply OCR using EasyOCR with specific options
easy_opts = EasyOCROptions(
    paragraph=False,
)
page.apply_ocr(engine='easyocr', languages=['en'], min_confidence=0.1, options=easy_opts)

paddle_opts = PaddleOCROptions(
    use_angle_cls=False,
    det_db_thresh=0.3,
)
page.apply_ocr(engine='paddle', languages=['en'], options=paddle_opts)

surya_opts = SuryaOCROptions()
page.apply_ocr(engine='surya', languages=['en'], min_confidence=0.5, detect_only=True, options=surya_opts)

from natural_pdf.ocr import PaddleOCROptions, EasyOCROptions, SuryaOCROptions # Re-apply OCR using EasyOCR with specific options easy_opts = EasyOCROptions( paragraph=False, ) page.apply_ocr(engine='easyocr', languages=['en'], min_confidence=0.1, options=easy_opts) paddle_opts = PaddleOCROptions( use_angle_cls=False, det_db_thresh=0.3, ) page.apply_ocr(engine='paddle', languages=['en'], options=paddle_opts) surya_opts = SuryaOCROptions() page.apply_ocr(engine='surya', languages=['en'], min_confidence=0.5, detect_only=True, options=surya_opts)

Detecting bboxes:   0%|                                                                                                           | 0/1 [00:00<?, ?it/s]

Detecting bboxes: 100%|███████████████████████████████████████████████████████████████████████████████████████████████████| 1/1 [00:00<00:00,  2.02it/s]

Detecting bboxes: 100%|███████████████████████████████████████████████████████████████████████████████████████████████████| 1/1 [00:00<00:00,  2.02it/s]

Out[5]:

<Page number=1 index=0>

Interactive OCR Correction / Debugging¶

If OCR results aren't perfect, you can use the bundled interactive web application (SPA) to review and correct them.

1. Package the data: After running apply_ocr (or apply_layout), use create_correction_task_package to create a zip file containing the PDF images and detected elements.

   from natural_pdf.utils.packaging import create_correction_task_package
   
   page.apply_ocr()
   
   create_correction_task_package(pdf, "correction_package.zip", overwrite=True)
   

2. Run the SPA: Navigate to the SPA directory within the installed natural_pdf library in your terminal and start a simple web server.

3. Use the SPA: Open http://localhost:8000 in your browser. Drag the correction_package.zip file onto the page to load the document. You can then click on text elements to correct the OCR results.

Working with Multiple Pages¶

Apply OCR or layout analysis to all pages using the PDF object.

In [6]:

# Process all pages in the document

# Apply OCR to all pages (example using EasyOCR)
pdf.apply_ocr(engine='easyocr', languages=['en'])
print(f"Applied OCR to {len(pdf.pages)} pages.")

# Or apply layout analysis to all pages (example using Paddle)
# pdf.apply_layout(engine='paddle')
# print(f"Applied Layout Analysis to {len(pdf.pages)} pages.")

# Extract text from all pages (uses OCR results if available)
all_text_content = pdf.extract_text(page_separator="\\n\\n---\\n\\n")

print(f"\nCombined text from all pages:\n{all_text_content[:500]}...")

# Process all pages in the document # Apply OCR to all pages (example using EasyOCR) pdf.apply_ocr(engine='easyocr', languages=['en']) print(f"Applied OCR to {len(pdf.pages)} pages.") # Or apply layout analysis to all pages (example using Paddle) # pdf.apply_layout(engine='paddle') # print(f"Applied Layout Analysis to {len(pdf.pages)} pages.") # Extract text from all pages (uses OCR results if available) all_text_content = pdf.extract_text(page_separator="\\n\\n---\\n\\n") print(f"\nCombined text from all pages:\n{all_text_content[:500]}...")

Applied OCR to 1 pages.

Combined text from all pages:
Red (RGB tuple )
Jungle Health and Safety Inspection Service
INS-UPZONS INCLAIR
Site: Durham's Meatpacking   Chicago, IIL.
Date: February 3, 1905
Violation Count:
Summary: Worst of any, however; were the fertilizer men, and those who served in the cooking rooms.
These people could not be shown to the visitorfor the odor of a fertilizer man would scare any ordinary
visitor at a hundred yards, and as for the other men, who worked in tank rooms full of steam; and in
some of which there were open va...

Saving PDFs with Searchable Text¶

After applying OCR to a PDF, you can save a new version of the PDF where the recognized text is embedded as an invisible layer. This makes the text searchable and copyable in standard PDF viewers.

Use the save_searchable() method on the PDF object:

In [7]:

from natural_pdf import PDF

input_pdf_path = "https://github.com/jsoma/natural-pdf/raw/refs/heads/main/pdfs/needs-ocr.pdf"

pdf = PDF(input_pdf_path)
# Apply OCR to all pages before saving
# Use desired engine and options
pdf.apply_ocr(engine='easyocr', languages=['en'])

pdf.save_pdf("needs-ocr-searchable.pdf", ocr=True)

print("Saved searchable PDF to needs-ocr-searchable.pdf")

from natural_pdf import PDF input_pdf_path = "https://github.com/jsoma/natural-pdf/raw/refs/heads/main/pdfs/needs-ocr.pdf" pdf = PDF(input_pdf_path) # Apply OCR to all pages before saving # Use desired engine and options pdf.apply_ocr(engine='easyocr', languages=['en']) pdf.save_pdf("needs-ocr-searchable.pdf", ocr=True) print("Saved searchable PDF to needs-ocr-searchable.pdf")

CropBox missing from /Page, defaulting to MediaBox

Using CPU. Note: This module is much faster with a GPU.

Saved searchable PDF to needs-ocr-searchable.pdf

This creates needs-ocr-searchable.pdf, which looks identical to the original but now has a text layer corresponding to the OCR results. You can adjust the rendering resolution used during saving with the dpi parameter (default is 300).

OCR integration enables you to work with scanned documents, historical archives, and image-based PDFs that don't have embedded text. By combining OCR with natural-pdf's layout analysis capabilities, you can turn any document into structured, searchable data.