Image Processing Apparatus High-Frequency Contrast Correction

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Solution Overview

Problem

High dynamic range (HDR) image processing technologies face challenges in noise suppression during contrast correction, particularly emphasizing noise in low luminance regions, leading to images that are more noticeably affected by noise than before.

Innovation Solution

An image processing apparatus with a detection unit to identify specific image regions and a correction unit that adjusts high-frequency values of pixels above a certain threshold to reduce noise influence, thereby weakening high-frequency contrast.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If contrast correction is performed on HDR image data using conventional methods, then the luminance contrast is improved, but noise is emphasized in low luminance regions

Engineering Contradiction:

Improveluminance contrastVSAvoidnoise emphasis

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The image data is divided into multiple luminance regions (first region with lower luminance, second region with higher luminance). Different contrast correction strengths are applied to each region, with weaker correction in the first region to avoid noise emphasis and stronger correction in the second region to improve overall luminance contrast.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different processing characteristics are applied to different regions of the image based on their luminance levels. The first region (lower luminance) receives contrast correction with a smaller magnitude to preserve noise-free quality, while the second region (higher luminance) receives contrast correction with a larger magnitude to enhance visual contrast where noise is less perceptible.

Inventive Principle:

Principle #3Local quality

2Adaptability or versatility

If D range compression is performed to adapt HDR content to printing apparatus, then the dynamic range is reduced for compatibility, but the luminance contrast is reduced

Engineering Contradiction:

Improvedynamic range compatibilityVSAvoidluminance contrast

Core Design Contradiction:

Adaptability or versatilityVSIllumination intensity

Solution Approach 1:

Contrast correction is performed before or during the D range compression process to compensate for the contrast reduction that will occur. By pre-adjusting the contrast, especially in the second region with higher luminance values, the final compressed image maintains acceptable luminance contrast despite the dynamic range reduction.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The contrast correction magnitude is adjusted based on the luminance value range. For the second region with higher luminance values (which will be compressed more significantly), a larger contrast correction magnitude is applied to compensate for the anticipated contrast loss during D range compression to the printing apparatus's limited dynamic range.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11108999B2Image processing apparatus, image processing method, and non-transitory computer-readable storage medium

Publication Date: 2021.08.31 CANON KK

AI summary

An image processing apparatus, comprises: a detection unit configured to detect a predetermined region of an image from image data; and a correction unit configured to correct a value of luminance in the predetermined region detected by the detection unit. The correction unit corrects a high-frequency value out of a low-frequency value and the high-frequency value obtained from a luminance value of a pixel having a value of luminance higher than a predetermined threshold in the predetermined region so that a high-frequency contrast weakens.