Image Processing Device Local Black Level Correction
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Solution Overview
Problem
Existing image processing technologies face challenges in correctly correcting the black level of images, especially in scenes with strong light sources, leading to raised black levels and reduced visibility due to the uniform application of black level processing across the entire image.
Innovation Solution
An image processing device calculates a reference black level and illumination light component based on peripheral pixel values to perform localized black level correction before tone mapping, ensuring accurate black level adjustment and suppressing raised black levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If uniform black level processing is applied across the entire image, then the dark current of the image sensor can be corrected, but the local black level deviation around strong light sources cannot be corrected
Solution Approach 1:
The patent divides the image into multiple local regions and performs black level correction separately for each region. This segmentation allows the system to handle uniform dark current correction while also addressing local black level deviations around strong light sources, resolving the contradiction between uniform processing and local adaptability.
Solution Approach 2:
The patent applies different black level correction strategies to different regions of the image. Uniform correction is applied to general areas, while local adaptive correction is applied to regions around strong light sources. This local quality approach enables the system to maintain overall correction accuracy while adapting to local variations in black level characteristics.
2Illumination intensity
If a large gain is applied to dark portions during local tone correction, then visibility in dark areas is improved, but raised black levels occur and visibility is reduced
Solution Approach 1:
The patent performs black level correction as a preliminary step before local tone correction. By correcting the black level in advance, the system establishes an accurate baseline for subsequent gain application, preventing the raised black levels that would otherwise occur when large gains are applied to dark portions.
Solution Approach 2:
The patent applies preliminary black level correction to counteract potential raised black levels before they occur during tone correction. This preliminary anti-action ensures that when large gains are later applied to improve dark area visibility, the black level remains accurate and does not rise excessively.
3Adaptability or versatility
If local tone correction is performed to correct HDR image to SDR image, then display compatibility is improved, but raised black levels occur in dark portions
Solution Approach 1:
The patent segments the tone correction process into distinct stages: black level correction followed by local tone mapping. This segmentation allows the system to maintain display compatibility through HDR-to-SDR conversion while preventing raised black levels by ensuring accurate black level correction is performed first in each local region.
Solution Approach 2:
The patent performs black level correction as a preliminary action before local tone mapping. This preliminary correction establishes accurate black levels across the image, ensuring that subsequent tone correction for display compatibility does not introduce raised black levels in dark portions.
Data Source
AI summary
An image processing device includes a memory and a processor configured to calculate a reference black level and a reference illumination light component based on pixel values of peripheral pixels located around a target pixel for image processing using image data acquired by an imaging device, correct a black level of the target pixels based on the reference black level calculated by the processor, and perform a tone correction of the target pixels with the black level corrected based on the reference illumination light component calculated by the processor. Accordingly, even when a large gain is applied to a dark portion of an image in a local tone correction, it is possible to generate an image with high visibility in which an occurrence of raised black levels is suppressed.