Image Text Finder
How to Build an Automated PII or Keyword Redaction Pipeline with .NET

How to Build an Automated PII or Keyword Redaction Pipeline with .NET

Redacting personally identifiable information (PII) and sensitive keywords in scanned images is crucial for privacy, legal, and compliance operations. Aspose.OCR Image Text Finder for .NET makes it possible to automate detection and redaction in batch workflows.

Real-World Problem

Manual redaction of confidential data in scanned archives is slow, error-prone, and costly. Automation is needed to ensure reliable and consistent masking for compliance and privacy audits.

Solution Overview

Automatically detect PII or keywords using OCR, then mask, blur, or replace them in the image and save the redacted results—ensuring privacy and security.

Prerequisites

  1. Visual Studio 2019 or later
  2. .NET 6.0 or later (or .NET Framework 4.6.2+)
  3. Aspose.OCR for .NET from NuGet
  4. PII or keyword list in a text file
PM> Install-Package Aspose.OCR

Step-by-Step Implementation

Step 1: Prepare PII/Keyword List and Input Images 

List<string> piiList = new List<string>(File.ReadAllLines("pii_keywords.txt"));
string[] files = Directory.GetFiles("./input", "*.png");

Step 2: Search for PII/Keywords 

RecognitionSettings settings = new RecognitionSettings();
settings.Language = Language.English;
AsposeOcr ocr = new AsposeOcr();
foreach (string file in files)
{
    foreach (string pii in piiList)
    {
        bool found = ocr.ImageHasText(file, pii, settings);
        if (found)
        {
            // Proceed to redact in Step 3
        }
    }
}

Step 3: Redact or Mask Detected Terms

  • While Aspose.OCR detects terms, redaction must be applied with image libraries (e.g., System.Drawing, SkiaSharp).
// Example using System.Drawing to overlay black box (simplified)
using (var image = new Bitmap(file))
{
    using (var g = Graphics.FromImage(image))
    {
        // Locate/estimate bounding box for found term (requires mapping OCR region, see docs/API)
        // g.FillRectangle(Brushes.Black, x, y, width, height);
    }
    image.Save($"./redacted/redacted_{Path.GetFileName(file)}");
}

Step 4: Log Redacted Files 

File.AppendAllText("redaction_log.csv", $"{file},{pii},redacted\n");

Step 5: Complete Batch Workflow Example 

using Aspose.OCR;
using System;
using System.Collections.Generic;
using System.IO;
using System.Drawing;

class Program
{
    static void Main(string[] args)
    {
        List<string> piiList = new List<string>(File.ReadAllLines("pii_keywords.txt"));
        string[] files = Directory.GetFiles("./input", "*.png");
        RecognitionSettings settings = new RecognitionSettings();
        settings.Language = Language.English;
        AsposeOcr ocr = new AsposeOcr();
        foreach (string file in files)
        {
            foreach (string pii in piiList)
            {
                bool found = ocr.ImageHasText(file, pii, settings);
                if (found)
                {
                    // Redact by overlay (simplified; see docs for bounding box)
                    using (var image = new Bitmap(file))
                    using (var g = Graphics.FromImage(image))
                    {
                        // Example: Draw rectangle where text is found (requires OCR region info)
                        // g.FillRectangle(Brushes.Black, x, y, width, height);
                        // Save redacted copy
                        image.Save($"./redacted/redacted_{Path.GetFileName(file)}");
                    }
                    File.AppendAllText("redaction_log.csv", $"{file},{pii},redacted\n");
                }
            }
        }
    }
}

Note: For accurate region mapping, use Aspose.OCR’s recognition region APIs to get coordinates of detected text blocks, then mask precisely.

Use Cases and Applications

Legal and Compliance

Automate redaction of contracts, HR files, and regulated documents.

Privacy Audits

Ensure no PII leaks in scanned archives, onboarding, or evidence files.

Batch DLP (Data Loss Prevention)

Stop accidental sharing or storage of sensitive info in scanned images.

Common Challenges and Solutions

Challenge 1: Locating Precise Text Regions

Solution: Use OCR text region output and map to image coordinates for masking.

Challenge 2: False Positives/Negatives

Solution: Tune keyword lists, validate redacted images, and run audits.

Challenge 3: Batch Job Size

Solution: Parallelize and automate error handling for scale.

Performance Considerations

  • Region calculation and image write may be slow for large batches—use async if needed
  • Log all redactions for compliance review

Best Practices

  1. Test region mapping accuracy with varied images
  2. Regularly update keyword lists for new PII patterns
  3. Secure both original and redacted files
  4. Validate with manual spot-checks

Advanced Scenarios

Scenario 1: Blur Instead of Blackout

Use image filters to blur detected regions for more subtle masking.

Scenario 2: Custom Redaction/Replacement Text

Overlay custom label (e.g., “REDACTED”) instead of black box.

Conclusion

Aspose.OCR Image Text Finder for .NET empowers you to automate PII/keyword redaction at scale—reducing legal risk and ensuring privacy across image archives.

For precise region APIs and redaction integration, see Aspose.OCR for .NET API Reference .

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