OCR File
API Documentation

Overview

The OCR File API extracts text from PDF and image documents using pdfplumber and Tesseract OCR. It supports 11 languages, PDF and common image formats up to 50MB, and provides additional document-processing tools: replacing text in PDFs, creating searchable PDFs from scans, and converting extracted content into editable Word documents.

Base URL & Authentication

Base URL

https://api.chemhub.com/api/v1

Authentication

Include your API credentials in every request header.

X-API-Key: your_api_key
X-API-Secret: your_secret
Content-Type: application/json

Get API Keys

Follow these steps to obtain your API credentials:

Endpoints

Health Check

Health check endpoint to verify the OCR File service status, available backends, supported formats, and languages.

Response

{
  "success": true,
  "status": "healthy",
  "ocr_file_available": true,
  "pdfplumber": true,
  "pdf2image": true,
  "pytesseract": true,
  "fpdf": true,
  "supported_formats": [".pdf", ".jpg", ".jpeg", ".png", ".bmp", ".tiff", ".tif"],
  "ocr_languages": ["eng", "spa", "fra", "deu", "ita", "por", "rus", "chi_sim", "chi_tra", "jpn", "kor"],
  "max_file_size_mb": 50,
  "timestamp": "2026-08-07T12:00:00"
}

Code Examples

import requests

url = "https://api.chemhub.com/api/v1/ocr_file/health"

headers = {
    "X-API-Key": "your_api_key",
    "X-API-Secret": "your_secret"
}

res = requests.get(url, headers=headers)
print(res.json())

curl -X GET https://api.chemhub.com/api/v1/ocr_file/health \
-H "X-API-Key: your_api_key" \
-H "X-API-Secret: your_secret"

fetch('https://api.chemhub.com/api/v1/ocr_file/health', {
  method: 'GET',
  headers: {
    'X-API-Key': 'your_api_key',
    'X-API-Secret': 'your_secret'
  }
})
.then(res => res.json())
.then(console.log);

Extract Text from PDF or Image

Extract text from a PDF or image file. Enable OCR to capture text from scanned or image-based pages. Upload the file as multipart/form-data.

Form Parameters

Response

{
  "success": true,
  "result": {
    "text": "Hello world. This is the extracted document content.",
    "page_count": 2,
    "characters": 87
  },
  "ocr_used": false,
  "language": "eng",
  "processing_time_ms": 245.13
}

cURL Example

curl -X POST "https://api.chemhub.com/api/v1/ocr_file/extract_text" \
  -H "X-API-Key: your_api_key" \
  -H "X-API-Secret: your_secret" \
  -F "file=@document.pdf" \
  -F "use_ocr=false" \
  -F "language=eng" \
  -F "dpi=300"

Code Examples

import requests

url = "https://api.chemhub.com/api/v1/ocr_file/extract_text"

headers = {
    "X-API-Key": "your_api_key",
    "X-API-Secret": "your_secret"
}

with open("document.pdf", "rb") as f:
    files = {"file": f}
    data = {"use_ocr": "true", "language": "eng", "dpi": "300"}
    response = requests.post(url, headers=headers, files=files, data=data)

if response.status_code == 200:
    result = response.json()
    print("Extracted text:")
    print(result.get("result", {}).get("text"))
else:
    print(response.json())

const form = new FormData();
form.append('file', fileInput.files[0]);
form.append('use_ocr', 'true');
form.append('language', 'eng');
form.append('dpi', '300');

fetch('https://api.chemhub.com/api/v1/ocr_file/extract_text', {
  method: 'POST',
  headers: {
    'X-API-Key': 'your_api_key',
    'X-API-Secret': 'your_secret'
  },
  body: form
})
.then(res => res.json())
.then(data => console.log(data.result.text));

OCR Image

Extract text from a single image file using Tesseract OCR. Upload the file as multipart/form-data.

Form Parameters

Response

{
  "success": true,
  "result": "The text recognized from the image.",
  "language": "eng",
  "processing_time_ms": 412.87
}

cURL Example

curl -X POST "https://api.chemhub.com/api/v1/ocr_file/ocr_image" \
  -H "X-API-Key: your_api_key" \
  -H "X-API-Secret: your_secret" \
  -F "file=@scan.png" \
  -F "language=eng"

Replace Text in PDF

Replace occurrences of text inside a PDF and download the modified document. Upload the file as multipart/form-data with the replacements supplied as a JSON string.

Form Parameters

Replacements Example

[
  {"find": "Acme Corp", "replace": "ChemHub"},
  {"find": "2025", "replace": "2026"}
]

cURL Example

curl -X POST "https://api.chemhub.com/api/v1/ocr_file/replace_text" \
  -H "X-API-Key: your_api_key" \
  -H "X-API-Secret: your_secret" \
  -F "file=@document.pdf" \
  -F 'replacements=[{"find":"Acme Corp","replace":"ChemHub"}]' \
  --output replaced.pdf

Create Searchable PDF

Convert a scanned PDF into a searchable PDF by running OCR and embedding a text layer. Upload the file as multipart/form-data.

Form Parameters

cURL Example

curl -X POST "https://api.chemhub.com/api/v1/ocr_file/create_searchable" \
  -H "X-API-Key: your_api_key" \
  -H "X-API-Secret: your_secret" \
  -F "file=@scanned.pdf" \
  -F "language=eng" \
  -F "dpi=300" \
  --output searchable.pdf

Extract to Word

Extract text from a document and convert it into a Microsoft Word (.docx) file. Upload the file as multipart/form-data. Generated documents are also available for download via GET /ocr_file/download_word_document/{filename}.

Form Parameters

Response

{
  "success": true,
  "result": "Word document generated successfully.",
  "processing_time_ms": 1204.55
}

cURL Example

curl -X POST "https://api.chemhub.com/api/v1/ocr_file/extract_to_word" \
  -H "X-API-Key: your_api_key" \
  -H "X-API-Secret: your_secret" \
  -F "file=@document.pdf" \
  -F "use_ocr=true" \
  -F "language=eng" \
  -F "dpi=300"

Python SDK

Complete Python SDK covering health check, text extraction, image OCR, text replacement, searchable PDF creation, and Word conversion.

import requests
import json

BASE_URL = "https://api.chemhub.com/api/v1"
API_KEY = "YOUR_API_KEY"
API_SECRET = "YOUR_API_SECRET"

headers = {
    "X-API-Key": API_KEY,
    "X-API-Secret": API_SECRET
}

# --- Health Check ---
def check_health():
    return requests.get(f"{BASE_URL}/ocr_file/health", headers=headers).json()

# --- Extract text from a PDF or image ---
def extract_text(file_path, use_ocr=False, language="eng", dpi=300):
    with open(file_path, "rb") as f:
        files = {"file": f}
        data = {
            "use_ocr": "true" if use_ocr else "false",
            "language": language,
            "dpi": str(dpi)
        }
        response = requests.post(
            f"{BASE_URL}/ocr_file/extract_text",
            headers=headers,
            files=files,
            data=data
        )
    if response.status_code == 200:
        result = response.json()
        print(result.get("result", {}).get("text"))
        return result.get("result", {}).get("text")
    print(f"Error: {response.status_code} - {response.text}")
    return None

# --- OCR a single image ---
def ocr_image(file_path, language="eng"):
    with open(file_path, "rb") as f:
        files = {"file": f}
        data = {"language": language}
        response = requests.post(
            f"{BASE_URL}/ocr_file/ocr_image",
            headers=headers,
            files=files,
            data=data
        )
    if response.status_code == 200:
        return response.json().get("result")
    print(f"Error: {response.status_code} - {response.text}")
    return None

# --- Replace text in a PDF ---
def replace_text(file_path, replacements, output_path="replaced.pdf"):
    with open(file_path, "rb") as f:
        files = {"file": f}
        data = {"replacements": json.dumps(replacements)}
        response = requests.post(
            f"{BASE_URL}/ocr_file/replace_text",
            headers=headers,
            files=files,
            data=data
        )
    if response.status_code == 200:
        with open(output_path, "wb") as out:
            out.write(response.content)
        print(f"Saved: {output_path}")
        return output_path
    print(f"Error: {response.status_code} - {response.text}")
    return None

# --- Create a searchable PDF from a scan ---
def create_searchable(file_path, language="eng", dpi=300, output_path="searchable.pdf"):
    with open(file_path, "rb") as f:
        files = {"file": f}
        data = {"language": language, "dpi": str(dpi)}
        response = requests.post(
            f"{BASE_URL}/ocr_file/create_searchable",
            headers=headers,
            files=files,
            data=data
        )
    if response.status_code == 200:
        with open(output_path, "wb") as out:
            out.write(response.content)
        print(f"Saved: {output_path}")
        return output_path
    print(f"Error: {response.status_code} - {response.text}")
    return None

# --- Extract to Word ---
def extract_to_word(file_path, language="eng", dpi=300):
    with open(file_path, "rb") as f:
        files = {"file": f}
        data = {"use_ocr": "true", "language": language, "dpi": str(dpi)}
        response = requests.post(
            f"{BASE_URL}/ocr_file/extract_to_word",
            headers=headers,
            files=files,
            data=data
        )
    if response.status_code == 200:
        return response.json()
    print(f"Error: {response.status_code} - {response.text}")
    return None

# --- Test all endpoints ---
if __name__ == "__main__":
    print("=== OCR FILE API TEST ===")

    health = check_health()
    print(f"Health: {health.get('status', 'unknown')}")
    print(f"Languages: {health.get('ocr_languages', [])}")

    print("\n1. Extracting text from a PDF:")
    extract_text("document.pdf", use_ocr=True, language="eng")

    print("\n2. Replacing text in a PDF:")
    replace_text("document.pdf", [{"find": "Acme Corp", "replace": "ChemHub"}])

    print("\n3. Creating a searchable PDF:")
    create_searchable("scanned.pdf", language="eng")

Errors & Status Codes

Error Response Format

{
  "success": false,
  "error": "Unsupported language",
  "message": "Unsupported language. Supported: eng, spa, fra, deu, ita, por, rus, chi_sim, chi_tra, jpn, kor"
}

Status Codes

Limitations