Tips for Better OCR Results

Advanced Guide: Field-Tested Pro Tips for Rock-Solid OCR

These expert techniques expand on the basics above to help you capture better inputs, choose the right pre-processing steps, and review results efficiently. Everything here works with the current browser-only design—no extra software required.

1) Capture Playbook (Phone & Scanner)

• Fill the frame: Let the document occupy 80–90% of the image so small text stays legible.
• Keep it flat: Place paper on a matte surface; avoid glass that creates glare and double reflections.
• Square the edges: Align the camera parallel to the page; if you see a trapezoid, you’re off-axis.
• Stability: Use both hands, brace elbows, or rest the phone on a stack of books; shoot after a 1–2 s hold.
• Lighting: Prefer indirect daylight from two sides; if using lamps, place them at 45° from the document to avoid hotspots.
• Camera options: Turn HDR off for small text (prevents haloing), disable flash indoors (prevents specular glare), and enable gridlines for alignment.
• Scanner DPI: 300 DPI for general text; 400–600 for tiny footnotes or dot-matrix receipts.

2) Geometry & Composition

• Straight horizon: The top/bottom edges of the page should be parallel to the image edge.
• Perspective check: Parallel lines should look parallel; if not, step back and zoom in slightly to reduce lens distortion.
• Margin control: Keep a slim border (5–10 mm) so edge characters aren’t clipped after cropping.

3) Lighting Techniques That Always Help

• Diffuse first: Place thin white paper over a harsh lamp to soften shadows.
• Kill glare: Tilt the document a few degrees or rotate it until bright streaks vanish.
• Avoid color casts: If the scene is very warm/cool, switch your camera to a neutral white balance.

4) Quick Pre-Processing Cheatsheet

• Grayscale first: Convert to grayscale to remove subpixel color fringing from screenshots/UI text.
• Contrast stretch: Boost mid-tones gently so thin strokes pop; avoid extremes that thicken letters.
• Deskew: If baselines slope, rotate by small increments (±0.5–2°) until lines are level.
• Binarize when noisy: Apply a light threshold only for very messy backgrounds; on clean prints, binarization can lose detail—use grayscale instead.
• Morphological close (receipts): Slightly “heal” broken dot-matrix characters before OCR.
• One resize, once: Downscale huge images to a working width (e.g., 2000–3000 px long edge) to speed up recognition without sacrificing legibility.

5) Layout-Specific Tactics

• Multi-column articles: Split per column and process in reading order.
• Tables: Crop tight to the grid; run OCR and then reconstruct as CSV if needed.
• Forms: Process in blocks (name, address, totals). Validate each block with simple patterns (dates, phone numbers, amounts).
• Stamps/watermarks: If decorative and overpowering, lightly mask before OCR to preserve edges.

6) Document Type Playbook

• Receipts (thermal/dot-matrix): Use diffuse light, flatten paper curls, apply gentle contrast and closing; focus on the items and totals region.
• ID cards & badges: Remove glossy sleeves; shoot at a slight angle to avoid reflection, then deskew; crop MRZ or code lines separately.
• Books/magazines: Press near the spine to reduce curve; if curvature persists, capture two halves and merge text later.
• Whiteboards: Shoot straight on, disable HDR, bump contrast; black markers on white boards OCR best.
• Slides & projectors: Photograph the slide directly from the screen center; avoid keystone by stepping back and zooming.
• Screenshots: Prefer PNG; crop to the exact text area to avoid UI clutter.

7) Language-Aware Tips

• Single dominant language: If possible, set the recognition language explicitly for higher accuracy.
• Mixed scripts: Segment the image into regions (e.g., Latin vs. Arabic) and process separately to reduce look-alike confusions.
• Thai/CJK without spaces: Keep punctuation; it improves boundary detection.

8) Quality Gates Before You OCR

• Legibility test: At 100% zoom, you should easily count the dots in “i” or see the crossbar in “t”.
• x-height target: Lowercase height around 20–30 px after any resizing is a good rule of thumb.
• Blur check: Thin hairlines shouldn’t smear across pixels; if they do, re-shoot.
• Contrast check: Background noise should be faint; if speckled, lightly denoise or reshoot under steadier light.

9) Post-OCR Triage That Saves Time

• Scan hotspots first: Headers, totals, codes, and proper names are the most visible errors.
• Digits & separators: Confirm decimal/thousands separators and currency symbols; normalize if needed.
• Spell-fix only when paused: Do quick visual passes first; deeper edits later.
• Keep a changelog: If you correct systematic mistakes (e.g., “0↔O”), note them so your next capture avoids them.

10) Batch Workflow & Naming Discipline

• Consistent names: YYYY-MM-DD_Project_Page-001.png keeps pages in order and helps later audits.
• One change per step: Resize → deskew → contrast; avoid re-encoding JPEGs multiple times.
• Sample first: Run 2–3 representative pages before a big batch to catch surprises.

11) Handwriting: What’s Realistic

General OCR is tuned for printed text. For handwritten notes, prefer block letters, thicker markers on white paper, and larger character size. If you only need numbers or short codes, treat them as a separate crop and process with printed text settings.

12) Troubleshooting Decision Tree

• Output is gibberish: Check rotation; then re-shoot with steadier light and higher contrast.
• Numbers wrong (0↔O, 1↔l): Increase sharpness slightly or reshoot; verify separators and currency.
• Words run together: Text may be too small or compressed; upscale modestly or capture closer.
• Reading order off: It’s a layout issue—split columns/tables and process per region.
• Only some areas fail: Crop and retry the weak region; glare or shadows often affect a corner more than the whole page.

13) Accessibility & Usability Tips

• Use keyboard navigation to move from upload to Start OCR, then to Copy/Download quickly.
• If you rely on screen readers, keep the capture simple: high contrast and few decorative elements aid both OCR and TTS.

14) Privacy-Friendly Habits

• Review results for sensitive data before sharing.
• Prefer local exports and clear the workspace when finished.
• Avoid screenshots that accidentally include unrelated private windows or notifications.

15) Quick Checklists

• Capture: Flat paper, even light, square edges, steady hold.
• Prepare: Grayscale, deskew, gentle contrast, single resize.
• Process: Split complex layouts; set language when known.
• Review: Verify digits, names, totals; normalize separators.

Summary

Great OCR starts before you click “Start”—with clean capture, simple geometry, and a light touch on preprocessing. Split tricky layouts, set the right language, and review just the hotspots. These habits produce clear, auditable text faster and with fewer surprises.