Image Processing Apparatus Multi-Illuminant White Balance

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Solution Overview

Problem

Conventional image signal processors (ISPs) face challenges in accurately handling images with multiple correlated color temperatures (CCTs) from different light sources, as they often apply a single white balance gain to the entire image, which may not be suitable for all CCTs, leading to suboptimal color processing.

Innovation Solution

An image processing method and apparatus that estimates candidate CCT values and location values using a location-based multi-illuminant estimation unit, refines these values through filtering and mapping processes, and calculates a CCT matrix to perform color processing, including automatic white balance and color correction, tailored to specific sub-units of the image.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single white balance gain is applied to the entire image, then the processing complexity is low, but the color accuracy for images with multiple CCTs deteriorates

Engineering Contradiction:

Improveprocessing complexityVSAvoidcolor accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The image is divided into multiple sub-units, and a CCT matrix is constructed where each element corresponds to a specific sub-unit. This allows different white balance gains to be applied to different regions with different illuminants, resolving the contradiction between processing simplicity and color accuracy for multi-CCT images.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of applying a uniform white balance gain to the entire image, the patent applies location-specific white balance gains through the CCT matrix. Each sub-unit receives a tailored gain based on its local illuminant characteristics, improving color accuracy while maintaining reasonable processing complexity through systematic organization.

Inventive Principle:

Principle #3Local quality

2Measurement precision

If a CCT matrix with refined candidate values is calculated, then the color processing accuracy is improved, but the computational complexity increases

Engineering Contradiction:

Improvecolor processing accuracyVSAvoidcomputational complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent performs preliminary filtering and mapping processes to refine candidate CCT values before final color processing. By pre-processing and organizing the CCT data into a structured matrix, the system reduces the complexity of subsequent color correction operations while maintaining high accuracy.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces complex iterative optimization methods with a systematic filtering and mapping approach. Instead of using computationally intensive algorithms to find optimal CCT values, the system uses predefined filtering criteria and mapping functions to efficiently refine candidate values, reducing computational burden while maintaining accuracy.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS8611656B2Image processing apparatus, image processing method and recording medium for storing program to execute the method

Publication Date: 2013.12.17 SAMSUNG ELECTRONICS CO LTD

AI summary

According to example embodiments, an image processing method includes estimating, using a location-based multi-illuminant estimation unit, candidate correlated color temperature values and location values of sub-units of an image, calculating, using the location-based multi-illuminant estimation unit, a correlated color temperature (CCT) matrix based on the candidate CCT values and the location values, and performing, using a color processing unit, color processing by using the CCT matrix.