Histogram Modification for Scanned Document Contrast

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Solution Overview

Problem

Traditional contrast adjustment methods for scanned documents with dark scanning borders are unreliable due to spikes in the image histogram, leading to ineffective enhancement of image quality.

Innovation Solution

The method modifies the histogram by reducing the number of black pixels caused by dark scanning borders, allowing for accurate contrast adjustment by extracting black connected components and updating the histogram, thereby improving contrast enhancement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional contrast adjustment methods are applied to scanned documents with dark scanning borders, then the contrast enhancement process can be performed, but the dark scanning borders create spikes in the histogram that make the contrast adjustment unreliable

Engineering Contradiction:

Improvereliability of contrast adjustmentVSAvoiddark scanning border spikes in histogram

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by modifying the histogram before contrast adjustment is performed. The method pre-processes the histogram data to remove or neutralize the effect of dark scanning borders, ensuring that subsequent contrast adjustment operates on clean, accurate histogram data without the interfering spikes caused by border artifacts

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent extracts and removes the harmful dark scanning border components from the histogram analysis. By identifying and excluding the border-related pixel values from the histogram calculation, the method isolates the useful image content from the harmful border artifacts, enabling reliable contrast adjustment

Inventive Principle:

Principle #2Taking out (Extraction)

2Measurement precision

If the histogram includes all pixels including those from dark scanning borders, then the histogram represents the complete image, but the contrast adjustment becomes unreliable due to border-induced spikes

Engineering Contradiction:

Improveaccuracy of histogram representationVSAvoidreliability of contrast adjustment

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies segmentation by dividing the image into distinct regions: the actual document content area and the scanning border area. By separately analyzing the histogram of the content area while excluding or separately handling the border area, the method achieves both accurate histogram representation for contrast adjustment and elimination of border-induced reliability issues

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS8155442B2Method and apparatus for modifying the histogram of an image

Publication Date: 2012.04.10 THE NEAT COMPANY INC

AI summary

A method and corresponding computing device and computer readable storage media containing instructions for modifying the histogram of a grayscale image to improve contrast by extracting black connected components from the grayscale image that touch at least one of the margins of the grayscale image, computing the histogram of the portion of the grayscale image covered by the extracted black connected components, and updating the histogram of the grayscale image by subtracting the histogram of the portion of the binary image covered by the extracted black connected components from the histogram of the grayscale image or by subtracting a function of number of pixels of the portion of the binary image covered by the extracted black connected components from the histogram of the grayscale image. The function may be a property of a document containing the grayscale image, such as the size of the document. In this case, pixels outside of the document boundaries are removed from the histogram during the updating of the histogram.