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Table 1 Tabulated summary of all pre-processing technique

From: Comparative study: enhancing legibility of ancient Indian script images from diverse stone background structures using 34 different pre-processing methods

Preprocessing technique

Description

Application in Stone Inscriptions

Thresholding

Techniques like Otsu’s Method, Niblack, and Sauvola adaptively establish thresholds, aiding in segmenting text from backgrounds and handling varied lighting conditions

Essential for segmenting inscribed content and adapting to diverse lighting conditions

Median filtering

Replaces pixel values with the median of neighboring pixels, reducing sudden noise caused by imperfections on stone surfaces

Effective in removing unwanted noise from scratches or imperfections on stone surfaces

Gaussian blur

Smooths images without compromising the integrity of inscribed text or details, reducing minor irregularities and noise

Useful for refining stone inscription images without losing essential details

CLAHE and gamma correction

Techniques optimizing contrast, controlling noise, and enhancing image quality, specifically adapted for stone inscriptions

Enhance readability and preservation of historical content in stone inscriptions

Resizing

Adjusts image dimensions for efficient computational processing, optimizing memory usage and retaining essential content details

Manages large image sizes while retaining critical information for analysis

Grayscale conversion

Converts images to grayscale, emphasizing contrast and intensity variations, focusing on the legibility of inscribed content

Helps in emphasizing contrast and clarity, aiding in the interpretation of inscriptions

Bilateral filtering

Smooths homogeneous regions while preserving edges and details within inscriptions, enhancing overall image quality

Improves image clarity while maintaining the integrity of intricate details

Morphological operations

Erosion, dilation, opening, and closing refine image structures, aid in edge detection, and manipulate inscription features

Vital in shaping, refining, and enhancing structural details within stone inscriptions

Edge detection

Techniques like Canny, LoG, and Sobel detect and highlight edges, aiding in capturing intricate details within inscriptions

Essential in uncovering and analyzing crucial features and details within stone inscriptions

K-means clustering

Segments inscribed content or distinguishes various elements within images, aiding in identifying patterns or text from non-text regions

Helps in segmenting and identifying different components or patterns within stone inscriptions

Denoising (Fast means, NLM)

Techniques reducing noise and enhancing image clarity, crucial for preserving critical details within the inscriptions

Mitigates noise interference, allowing for clearer analysis and interpretation of inscriptions