Hi ​@Uzumaki,

Here are some widely used preprocessing techniques beyond grayscale and contrast adjustments that can significantly improve document extraction accuracy for OCR and Intelligent Document Processing (IDP) systems:

1. Skew Correction (De-skewing):

Misaligned or tilted documents can confuse OCR engines. Correcting skew ensures text lines are horizontal, improving recognition accuracy. Tools: OpenCV’s getRotationMatrix2D or deskew algorithms.

2. Noise Reduction (De-speckling):

Removes specks, smudges, and background artifacts that mimic characters. Techniques include median filtering, Gaussian blur, or fastNlMeansDenoising in the OpenCV.

3. Binarization:

 Converts images to black-and-white for better text contrast. Otsu’s Thresholding or Adaptive Thresholding are common methods. This reduces complexity and improves OCR accuracy.

4. Image Scaling & DPI Normalization:

OCR engines perform best at 300 DPI. Resizing low-resolution images to at least 300 DPI improves recognition.

5. Cropping & Region of Interest (ROI):

Removes irrelevant borders, logos, or graphics that can confuse OCR. Focuses the engine on the text area only.

6. Thinning & Skeletonization:

Reduces character strokes to a single-pixel width. Useful for handwritten text or varying stroke widths.

7. Normalization:

Adjusts pixel intensity values to a standard range for consistent processing.

8. Advanced IDP Pre-processing:

De-speckling, binarization, and de-skewing combined with AI-based classification. IDP platforms like Automation Anywhere also use machine learning and NLP for intelligent classification and validation.

9. Contrast & Brightness Adjustment:

Enhances text visibility, especially for faint or low-contrast documents. Often combined with grayscale conversion.

10. Color Segmentation & Layer Separation:

For documents with colored backgrounds or watermarks, separating text layers improves OCR accuracy.

This is really helpful, I appreciate the effort put forth here. I will consider using some of these techniques in my own pre-processing.