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Henrik Jess Nielsen
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docs/snippets/php/configuration/image_preprocessing_config.php
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302
docs/snippets/php/configuration/image_preprocessing_config.php
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```php title="image_preprocessing_config.php"
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<?php
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declare(strict_types=1);
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/**
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* Image Preprocessing Configuration
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*
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* This example demonstrates image preprocessing options to improve OCR accuracy.
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* Preprocessing can significantly enhance text recognition quality for poor-quality scans.
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*/
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require_once __DIR__ . '/vendor/autoload.php';
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use Kreuzberg\Kreuzberg;
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use Kreuzberg\Config\ExtractionConfig;
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use Kreuzberg\Config\OcrConfig;
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use Kreuzberg\Config\ImagePreprocessingConfig;
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echo "Example 1: Default Image Preprocessing\n";
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echo "======================================\n";
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$config1 = new ExtractionConfig(
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ocr: new OcrConfig(
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backend: 'tesseract',
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language: 'eng',
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imagePreprocessing: new ImagePreprocessingConfig()
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)
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);
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echo "Default preprocessing settings:\n";
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echo "- Target DPI: 300 (standard for OCR)\n";
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echo "- Auto-rotate: Enabled\n";
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echo "- Denoise: Disabled\n\n";
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echo "Example 2: High DPI Configuration\n";
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echo "=================================\n";
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$config2 = new ExtractionConfig(
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ocr: new OcrConfig(
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backend: 'tesseract',
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language: 'eng',
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imagePreprocessing: new ImagePreprocessingConfig(
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targetDpi: 600
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)
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)
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);
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echo "Target DPI: 600\n";
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echo "Best for:\n";
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echo "- Very small text\n";
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echo "- High-quality scans\n";
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echo "- Documents with fine details\n";
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echo "Note: Higher DPI = slower processing, more memory\n\n";
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echo "Example 3: Lower DPI for Speed\n";
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echo "==============================\n";
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$config3 = new ExtractionConfig(
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ocr: new OcrConfig(
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backend: 'tesseract',
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language: 'eng',
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imagePreprocessing: new ImagePreprocessingConfig(
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targetDpi: 150
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)
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)
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);
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echo "Target DPI: 150\n";
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echo "Best for:\n";
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echo "- Large text\n";
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echo "- Low-resolution images\n";
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echo "- Fast processing needed\n";
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echo "Note: May reduce accuracy for small text\n\n";
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echo "Example 4: Manual Rotation Control\n";
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echo "==================================\n";
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$config4 = new ExtractionConfig(
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ocr: new OcrConfig(
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backend: 'tesseract',
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language: 'eng',
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imagePreprocessing: new ImagePreprocessingConfig(
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autoRotate: false
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)
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)
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);
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echo "Auto-rotate: Disabled\n";
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echo "Use when:\n";
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echo "- Images are already correctly oriented\n";
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echo "- Auto-rotation causes issues\n";
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echo "- Processing time is critical\n\n";
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echo "Example 5: Denoising for Poor Quality Scans\n";
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echo "===========================================\n";
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$config5 = new ExtractionConfig(
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ocr: new OcrConfig(
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backend: 'tesseract',
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language: 'eng',
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imagePreprocessing: new ImagePreprocessingConfig(
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targetDpi: 300,
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autoRotate: true,
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denoise: true
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)
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)
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);
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$kreuzberg = new Kreuzberg($config5);
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$result = $kreuzberg->extractFile('noisy_scan.pdf');
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echo "Denoising: Enabled\n";
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echo "Best for:\n";
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echo "- Poor quality scans\n";
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echo "- Fax documents\n";
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echo "- Images with background noise\n";
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echo "- Old or damaged documents\n";
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echo "\nExtracted text length: " . strlen($result->content) . " characters\n\n";
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echo "Example 6: Maximum Quality Configuration\n";
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echo "========================================\n";
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$config6 = new ExtractionConfig(
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ocr: new OcrConfig(
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backend: 'tesseract',
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language: 'eng',
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imagePreprocessing: new ImagePreprocessingConfig(
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targetDpi: 600,
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autoRotate: true,
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denoise: true
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)
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)
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);
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echo "Maximum quality preprocessing:\n";
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echo "- Target DPI: 600 (high quality)\n";
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echo "- Auto-rotate: Enabled\n";
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echo "- Denoise: Enabled\n";
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echo "\nBest for:\n";
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echo "- Very poor quality scans\n";
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echo "- Historical documents\n";
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echo "- Faded or damaged text\n";
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echo "- Critical accuracy requirements\n\n";
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echo "Example 7: Fast Processing Configuration\n";
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echo "========================================\n";
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$config7 = new ExtractionConfig(
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ocr: new OcrConfig(
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backend: 'tesseract',
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language: 'eng',
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imagePreprocessing: new ImagePreprocessingConfig(
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targetDpi: 200,
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autoRotate: false,
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denoise: false
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)
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)
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);
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echo "Fast processing configuration:\n";
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echo "- Target DPI: 200 (faster)\n";
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echo "- Auto-rotate: Disabled\n";
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echo "- Denoise: Disabled\n";
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echo "\nBest for:\n";
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echo "- High-volume processing\n";
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echo "- Good quality source images\n";
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echo "- Performance-critical applications\n\n";
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echo "Example 8: DPI Recommendations by Document Type\n";
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echo "===============================================\n";
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$standardConfig = new ImagePreprocessingConfig(targetDpi: 300);
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echo "Standard documents (letters, reports): 300 DPI\n";
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$newspaperConfig = new ImagePreprocessingConfig(targetDpi: 400);
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echo "Newspapers and magazines: 400 DPI\n";
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$bookConfig = new ImagePreprocessingConfig(targetDpi: 600);
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echo "Books with small text: 600 DPI\n";
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$receiptConfig = new ImagePreprocessingConfig(targetDpi: 300);
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echo "Receipts and forms: 300 DPI\n";
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$businessCardConfig = new ImagePreprocessingConfig(targetDpi: 400);
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echo "Business cards: 400 DPI\n";
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$faxConfig = new ImagePreprocessingConfig(
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targetDpi: 300,
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denoise: true
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);
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echo "Faxes: 300 DPI + denoising\n\n";
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echo "Example 9: Adaptive Configuration by Image Quality\n";
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echo "==================================================\n";
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function getPreprocessingConfig(string $quality): ImagePreprocessingConfig
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{
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return match ($quality) {
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'excellent' => new ImagePreprocessingConfig(
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targetDpi: 300,
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autoRotate: false,
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denoise: false
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),
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'good' => new ImagePreprocessingConfig(
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targetDpi: 300,
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autoRotate: true,
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denoise: false
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),
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'fair' => new ImagePreprocessingConfig(
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targetDpi: 400,
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autoRotate: true,
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denoise: true
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),
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'poor' => new ImagePreprocessingConfig(
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targetDpi: 600,
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autoRotate: true,
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denoise: true
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),
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default => new ImagePreprocessingConfig(),
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};
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}
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echo "Quality-based configurations:\n\n";
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echo "Excellent Quality:\n";
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echo "- DPI: 300, Auto-rotate: No, Denoise: No\n";
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echo "- Clean scans, properly oriented\n\n";
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echo "Good Quality:\n";
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echo "- DPI: 300, Auto-rotate: Yes, Denoise: No\n";
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echo "- May need rotation correction\n\n";
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echo "Fair Quality:\n";
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echo "- DPI: 400, Auto-rotate: Yes, Denoise: Yes\n";
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echo "- Some noise or quality issues\n\n";
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echo "Poor Quality:\n";
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echo "- DPI: 600, Auto-rotate: Yes, Denoise: Yes\n";
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echo "- Significant quality problems\n\n";
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echo "Example 10: Complete OCR Pipeline with Preprocessing\n";
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echo "===================================================\n";
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$config10 = new ExtractionConfig(
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ocr: new OcrConfig(
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backend: 'tesseract',
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language: 'eng',
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imagePreprocessing: new ImagePreprocessingConfig(
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targetDpi: 300,
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autoRotate: true,
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denoise: true
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)
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)
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);
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$result10 = (new Kreuzberg($config10))->extractFile('poor_quality_scan.pdf');
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echo "Processing pipeline:\n";
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echo "1. Load image\n";
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echo "2. Auto-detect orientation and rotate if needed\n";
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echo "3. Upscale/downscale to 300 DPI\n";
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echo "4. Apply denoising filter\n";
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echo "5. Perform OCR\n";
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echo "\nResults:\n";
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echo "- Extracted text: " . strlen($result10->content) . " characters\n";
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echo "- Pages: " . ($result10->metadata->pageCount ?? 'N/A') . "\n";
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echo "\n\nImage Preprocessing Parameters:\n";
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echo "================================\n";
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echo "- targetDpi: Target resolution in dots per inch\n";
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echo " * 150 DPI: Fast, lower quality\n";
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echo " * 300 DPI: Standard, good balance (RECOMMENDED)\n";
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echo " * 400 DPI: Better for small text\n";
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echo " * 600 DPI: Best quality, slower\n";
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echo "\n";
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echo "- autoRotate: Automatically detect and correct orientation\n";
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echo " * true: Recommended for most cases\n";
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echo " * false: Skip if images are already oriented\n";
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echo "\n";
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echo "- denoise: Apply noise reduction filter\n";
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echo " * true: Recommended for poor quality scans\n";
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echo " * false: Skip for clean images (faster)\n";
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echo "\n\nBest Practices:\n";
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echo "===============\n";
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echo "1. Start with 300 DPI as a baseline\n";
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echo "2. Enable auto-rotate unless you know images are correct\n";
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echo "3. Enable denoising for poor quality documents\n";
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echo "4. Use higher DPI (400-600) for small text\n";
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echo "5. Use lower DPI (150-200) when speed is critical\n";
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echo "6. Test different settings to find optimal balance\n";
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echo "7. Consider source quality when choosing settings\n";
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echo "8. Remember: Higher quality = slower processing + more memory\n";
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echo "\n\nPerformance vs Quality Trade-offs:\n";
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echo "==================================\n";
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echo "Fastest: DPI=150, AutoRotate=No, Denoise=No\n";
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echo "Balanced: DPI=300, AutoRotate=Yes, Denoise=No (RECOMMENDED)\n";
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echo "Quality: DPI=400, AutoRotate=Yes, Denoise=Yes\n";
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echo "Maximum: DPI=600, AutoRotate=Yes, Denoise=Yes\n";
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```
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