Image Processing Apparatus Histogram Extension Posterization

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Solution Overview

Problem

Existing image processing techniques fail to effectively generate a posterized image with a reduced tone number while maintaining a natural distribution of pixel values, leading to a loss of detail and a non-painterly appearance.

Innovation Solution

An image processing method involving a histogram extension processing unit that applies a first tone conversion characteristic to increase the variance of the histogram, followed by a posterization processing unit using a second tone conversion characteristic defined by a step function, to generate a posterized image with a reduced tone number.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a step function tone conversion characteristic is applied directly to the input image to reduce the tone number, then the posterization effect is achieved, but the histogram distribution becomes unnatural and detail is lost

Engineering Contradiction:

Improvetone number reduction efficiencyVSAvoidhistogram distribution naturalness

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent applies a first tone conversion characteristic (linear or gamma correction) before the posterization processing to preliminarily adjust the histogram distribution. This preliminary action ensures that pixel values are properly distributed across the tone range before the step function is applied, preventing loss of detail and maintaining natural appearance in the final posterized image.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The first tone conversion characteristic acts as an intermediary processing step between the input image and the posterization processing. It mediates the transformation by preparing the image data with appropriate histogram distribution, allowing the step function to work effectively without directly causing unnatural distribution or detail loss.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If tone conversion is applied to images with skewed tone distributions, then processing is performed, but the output image lacks painterly appearance and natural tone distribution

Engineering Contradiction:

Improveprocessing applicability to various input imagesVSAvoidoutput image quality

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The patent changes the parameter of tone conversion characteristic based on the input image properties. By selecting different first tone conversion characteristics (linear or gamma correction) and adjusting the second tone conversion characteristic (step function parameters), the system adapts to images with various tone distributions, transforming skewed distributions into natural-looking posterized results.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS8818094B2Image processing apparatus, image processing method and recording device recording image processing program

Publication Date: 2014.08.26 OLYMPUS CORPORATION(JP)

AI summary

An image processing apparatus includes a histogram extension processing unit for performing a first tone conversion processing on an input image using a first tone conversion characteristic so that a variance of a histogram of an image after the first tone conversion processing is larger than that of a histogram of the input image before the first tone conversion processing; and a posterization processing unit for performing a second tone conversion processing on the image processed in the histogram extension processing unit using a second tone conversion characteristic in which a relation of an output value to an input value is defined by a step function, thereby generating a posterized image whose tone number is reduced as compared with the image before the second tone conversion processing.