Handle Difficult Barcodes

This guide provides techniques for improving barcode detection in challenging conditions.

Common Challenges

• Poor lighting or shadows
• Blurry or out-of-focus images
• Small or distant barcodes
• Damaged or partially obscured barcodes
• Low contrast between bars and background

Improving Detection

Adjust Patch Size

For small or distant barcodes, use a smaller patch size:

locator: {
  patchSize: "small"  // or "x-small" for very small barcodes
}

Increase Resolution

Higher resolution provides more detail:

inputStream: {
  size: 1280,  // Larger processing size
  constraints: {
    width: { ideal: 1920 },
    height: { ideal: 1080 }
  }
}

Disable Half Sampling

For fine details, process at full resolution:

locator: {
  halfSample: false
}

Handling False Positives

Validate Results

Check result confidence and format:

Quagga.onDetected(function(result) {
  // Check if result has expected format
  if (result.codeResult.format !== 'ean_13') {
    return;  // Ignore unexpected formats
  }
  
  // Validate checksum externally if needed
  if (!validateBarcode(result.codeResult.code)) {
    return;
  }
  
  processBarcode(result.codeResult.code);
});

Require Multiple Reads

Confirm detection across multiple frames:

let lastCode = null;
let readCount = 0;

Quagga.onDetected(function(result) {
  const code = result.codeResult.code;
  
  if (code === lastCode) {
    readCount++;
    if (readCount >= 3) {
      // Confirmed detection
      processBarcode(code);
      readCount = 0;
    }
  } else {
    lastCode = code;
    readCount = 1;
  }
});

Using Debug Flags

Enable visual debugging to understand detection issues:

Quagga.init({
  debug: true,
  decoder: {
    debug: {
      drawBoundingBox: true,
      drawScanline: true
    }
  },
  locator: {
    debug: {
      showFoundPatches: true
    }
  }
});

See Use Debug Flags for complete details.

Related

• Configuration Reference - All configuration options
• Optimize Performance - Balance accuracy vs speed
• Use Debug Flags - Diagnostic tools

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