Dynamic Range Adjustment Using Pixel Classification

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Solution Overview

Problem

Conventional scanners and digital copiers statically adjust the black point of an image using a fixed offset value, leading to suboptimal dynamic range adjustment, where text may not be dark enough or shadow details may be lost, especially when relevant image data is not considered.

Innovation Solution

A dynamic range adjustment method and apparatus that determine the white and black points of an image, classify pixels, and calculate offset values based on pixel classification, allowing for dynamic adjustment of the image data using a white point detection module, black point detection module, pixel classification module, and offset value determination module.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a fixed offset value is used to adjust the black point, then the device complexity is reduced, but the image quality deteriorates due to non-optimal dynamic range adjustment

Engineering Contradiction:

Improveblack point adjustment mechanismVSAvoidimage quality

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent segments the image into different pixel types (text pixels, shadow pixels, highlight pixels) based on their intensity characteristics. By classifying pixels into distinct categories, the system applies different offset values to different segments, resolving the contradiction between simple fixed-offset adjustment and optimal image quality across all regions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements local quality adjustment by determining different black point offset values for different pixel types within the image. Text pixels receive one offset value, shadow pixels receive another, and highlight pixels receive yet another. This localized approach optimizes image quality for each region while maintaining manageable system complexity through automated classification.

Inventive Principle:

Principle #3Local quality

2Ease of operation

If a fixed offset value is used for black point adjustment, then the ease of operation is improved, but the adaptability deteriorates

Engineering Contradiction:

Improveblack point adjustment processVSAvoidimage type adaptability

Core Design Contradiction:

Ease of operationVSAdaptability or versatility

Solution Approach 1:

The system performs self-service by automatically classifying pixels and determining appropriate offset values without user intervention. The pixel classification module autonomously identifies text, shadow, and highlight regions, and the black point adjustment module automatically applies the correct offset values, maintaining ease of operation while achieving high adaptability to different image types.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent transitions from static fixed-offset adjustment to dynamic offset adjustment based on pixel classification. The system dynamically determines which pixels are text, shadow, or highlight and applies different offset values accordingly. This dynamic approach enables the system to adapt to various image types (documents, photographs, mixed content) while the automated process maintains ease of operation.

Inventive Principle:

Principle #15Dynamics

3Manufacturing precision

If dynamic pixel classification and multiple offset values are used, then the image quality is improved, but the device complexity increases

Engineering Contradiction:

Improvedynamic range adjustment qualityVSAvoidprocessing system complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by performing pixel classification before black point adjustment. The system预先 identifies and categorizes all pixels into text, shadow, and highlight groups, then applies the appropriate offset values in a subsequent processing step. This preliminary classification simplifies the overall complexity by organizing the work into distinct phases rather than requiring complex real-time decision-making during adjustment.

Inventive Principle:

Principle #10Preliminary action

4Adaptability or versatility

If dynamic pixel classification and multiple offset values are used, then the adaptability is improved, but the ease of operation deteriorates

Engineering Contradiction:

Improveimage type adaptabilityVSAvoidprocessing complexity

Core Design Contradiction:

Adaptability or versatilityVSEase of operation

Solution Approach 1:

The system achieves self-service by implementing automated pixel classification and offset value determination that requires no user input or manual configuration. The classification module automatically analyzes pixel intensity characteristics and assigns pixels to appropriate categories, while the adjustment module autonomously applies the correct offset values. This automation maintains ease of operation despite the enhanced adaptability to different image types.

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS7421143B2Systems and methods for optimal dynamic range adjustment of scanned images

Publication Date: 2008.09.02 XEROX CORP

AI summary

A method for dynamic range adjustment of image data of a captured image by determining a white point of an image. The method also involves determining a black point of the image, classifying pixels of the image, and determining an offset value for a pixel of the image based on the determined black point of the image and the determined classification of the pixel. Dynamic range adjustment of the image data is performed using the determined offset value for the pixels of the image and the determined white point of the image.