Image Processing Apparatus Blown-Out Highlight Detection

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Solution Overview

Problem

Existing methods for detecting blown-out highlights and blocked-up shadows in images are time-consuming and prone to omission, particularly in image pickup apparatuses, leading to inaccuracies in white balance and exposure control.

Innovation Solution

An image processing apparatus that calculates representative pixel values for blocks and uses a dual detection approach, one based on brightness and another on the difference between color represented by pixel values and gray, to identify blown-out highlights and blocked-up shadows, preventing detection omission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If detection is performed based on average pixel values of blocks, then processing speed is improved, but detection precision deteriorates due to detection omission

Engineering Contradiction:
Improveprocessing speedVSAvoiddetection precision
Core Design Contradiction:
ProductivityVSMeasurement precision

Solution Approach 1:

The image is divided into multiple blocks, and representative pixel values are calculated for each block. This segmentation allows parallel processing of blocks while maintaining detection accuracy through subsequent pixel-level verification in suspected blocks.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

Different detection strategies are applied to different regions: blocks are first screened using average pixel values, and only blocks with representative values near thresholds undergo detailed pixel-level inspection. This local adaptation of detection depth optimizes both speed and precision.

Inventive Principle:
Principle #3Local quality

2Measurement precision

If pixel-level detection is performed for all pixels, then detection precision is improved, but processing time increases

Engineering Contradiction:
Improvedetection precisionVSAvoidprocessing time
Core Design Contradiction:
Measurement precisionVSLoss of time

Solution Approach 1:

The image is divided into multiple blocks, and representative pixel values are calculated for each block. This segmentation allows parallel processing of blocks while maintaining detection accuracy through subsequent pixel-level verification in suspected blocks.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

Instead of performing exhaustive pixel-level detection on all blocks, the method applies partial action by conducting detailed pixel-level inspection only on blocks where representative pixel values are near thresholds, while using faster average-value comparison for other blocks.

Inventive Principle:
Principle #16Partial or excessive action

3Productivity

If hardware-based detection is implemented, then detection speed is improved, but device complexity increases due to larger circuit size

Engineering Contradiction:
Improvedetection speedVSAvoidcircuit size
Core Design Contradiction:
ProductivityVSDevice complexity

Solution Approach 1:

The patent replaces complex hardware-based pixel-level detection with a software-implemented two-stage algorithm that first uses block-level average value comparison and then applies pixel-level verification only when necessary, reducing hardware requirements while maintaining detection performance.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

4Device complexity

If block-level average value detection is used, then circuit size is reduced, but detection reliability deteriorates due to detection omission

Engineering Contradiction:
Improvecircuit sizeVSAvoiddetection reliability
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The image is divided into multiple blocks, and representative pixel values are calculated for each block. This segmentation allows parallel processing of blocks while maintaining detection accuracy through subsequent pixel-level verification in suspected blocks.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The method uses feedback by comparing representative pixel values against thresholds and automatically triggering pixel-level verification for blocks where the representative value is near the threshold, ensuring reliable detection without unnecessary processing.

Inventive Principle:
Principle #23Feedback

Data Source

PatentUS8682068B2Image processing apparatus, image processing method, and program
Publication Date: 2014.03.25 RENESAS ELECTRONICS CORP
  • US8682068B2 patent drawing
  • US8682068B2 patent drawing
  • US8682068B2 patent drawing

AI summary

A representative pixel value calculation unit (120) divides an image represented by raw data (D0) into a plurality of blocks and calculates representative pixel values (S) for each block. A detection unit (130) detects an object block which is a block including a blown-out highlight or a blocked-up shadow, from among the plurality of blocks. A B-detection unit (134) of the detection unit (130) performs a first detection processing for obtaining one of a difference between a color represented by the representative pixel values and gray, and a value that can approximately represent the difference, as a characteristic value, and for detecting, as the object block, a block in which the characteristic value is equal to or smaller than a first threshold. Consequently, blown-out highlights or blocked-up shadows included in an image can be detected at higher speed, and the omission of detection can be prevented.