Luminance Correction Curve Saturation Control

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing image brightness correction technologies fail to effectively consider the saturation and hue of images after correction, often resulting in altered impressions and contrast issues, such as excessive saturation or high contrast, which deviate from the original image characteristics.

Innovation Solution

A method and apparatus for creating a luminance conversion curve that takes into account the saturation and contrast of images by calculating a representative luminance value, dynamic range, and target luminance values, with the ability to revise the curve based on predicted saturation and contrast to maintain the original image's characteristics, using a look-up table to define output luminance values corresponding to input luminance values.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If luminance correction is applied to brighten dark images, then image brightness is improved, but image saturation increases excessively causing color distortion

Engineering Contradiction:

Improveimage brightnessVSAvoidimage saturation

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The patent implements a feedback mechanism by calculating predicted saturation values after luminance correction and comparing them against upper-limit saturation thresholds. When predicted saturation exceeds the threshold, the system automatically revises the luminance conversion curve to narrow the target dynamic range, thereby controlling saturation while maintaining brightness improvement.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent dynamically adjusts the target dynamic range parameters (target bright luminance value and target dark luminance value) based on predicted saturation levels. By changing these parameters adaptively, the system resolves the contradiction between brightening images and controlling saturation, allowing brightness correction while preventing excessive saturation through parameter optimization.

Inventive Principle:

Principle #35Parameter changes

2Illumination intensity

If luminance correction is applied to brighten dark images, then image brightness is improved, but image hue changes from the original

Engineering Contradiction:

Improveimage brightnessVSAvoidoriginal hue

Core Design Contradiction:

Illumination intensityVSLoss of information

Solution Approach 1:

The system uses feedback by predicting hue changes based on the luminance conversion curve and comparing predicted hue values against permitted hue ranges. When hue deviation exceeds acceptable limits, the system revises the conversion curve to preserve original hue characteristics while still achieving brightness correction.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent adjusts the luminance conversion curve parameters adaptively to maintain hue fidelity. By optimizing the target dynamic range and conversion curve shape based on predicted hue outcomes, the system achieves brightness improvement while preserving the original image hue within acceptable boundaries.

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

If the slope of the tone curve is increased to enhance contrast, then image contrast is improved, but extreme density correction occurs causing high-contrast artifacts

Engineering Contradiction:

Improveimage contrastVSAvoiddensity correction accuracy

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The patent implements dynamic control of the luminance conversion curve slope by adjusting the target dynamic range based on predicted saturation and contrast outcomes. Rather than using a fixed steep slope for contrast enhancement, the system adaptively modifies the curve shape to achieve desired contrast while preventing extreme density corrections that would cause artifacts.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system optimizes the luminance conversion curve parameters including slope and curvature based on predicted image quality metrics. By changing these parameters adaptively, the patent achieves contrast enhancement while maintaining density correction accuracy and avoiding the high-contrast artifacts that result from excessively steep curves.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS7715649B2Generation and adjustment of a luminance correction curve to prevent saturation of the image during contrast enhancement

Publication Date: 2010.05.11 FUJIFILM CORP

AI summary

A luminance conversion function calculating circuit calculates a luminance conversion function in order that a specific image contained in an image represented by image data to be processed will be made to have a desired brightness. Saturation of the specific image in a case where the applied image data has been subjected to a luminance correction based upon the calculated luminance conversion function is calculated and upper-limit saturation is calculated based upon an input value from the user. If the saturation of the specific image after the luminance correction thereof exceeds the upper-limit saturation, then a target dynamic range revising circuit narrows the range width of a target dynamic range that stipulates the luminance conversion function. The luminance conversion function is revised in a luminance conversion function revising circuit so as to have the narrowed range width.