Nepali OCR: How to Extract Devanagari and English Text from Scanned PDFs & Documents

Millions of government, legal, and academic archives in Nepal exist exclusively as paper scans or flat image PDFs. Without Optical Character Recognition (OCR), you cannot search through these archives using Ctrl+F, copy citations, or index records in digital management databases.

1. How Does Devanagari Optical Character Recognition Work?

OCR technology analyzes the patterns of light and dark pixels in a scanned page to identify individual letterforms and words. While Latin scripts (A–Z) are straightforward, recognizing Devanagari script presents unique computational challenges:

• The Shirorekha (शिरोरेखा - Top Horizontal Line): In Devanagari, letters in a word are joined by a continuous top line. The OCR engine must segment characters correctly beneath the shirorekha.
• Complex Ligatures & Conjuncts: Characters like ज्ञ, क्ष, त्र, and द्ध combine multiple consonants into distinct graphical shapes.
• Upper & Lower Diacritics (मात्रा): Vowel markers appear above, below, before, and after consonants, requiring multi-tier bounding box detection.

2. Best Practices for Scanning Documents for Maximum OCR Accuracy

To ensure 98%+ character recognition accuracy:

1. Ensure Flat Lighting: Avoid cast shadows from your hand or mobile phone when photographing papers.
2. Keep Text Straight: Even a 5-degree rotation skew degrades OCR accuracy. PDFNepal's engine applies auto-deskewing, but starting with a straight scan yields optimal output.
3. Scan at 300 DPI: High-resolution input ensures small diacritics (like anusvara dots and halantas) are cleanly resolved.