Dynamic Range Enhancement via Adaptive Exposure Selection
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Solution Overview
Problem
Image sensing devices have a limited dynamic range compared to traditional film, leading to over-exposed or under-exposed portions in images, especially in scenes with wide dynamic ranges, and High Dynamic Range (HDR) imaging methods face challenges with motion artifacts and display compatibility.
Innovation Solution
A method and apparatus that enhance the local dynamic range of images by selecting regions for enhancement, applying exposure weights, and using exposure bracketed images to generate weight maps, allowing for interactive user control and reduction of ghosting artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If multiple still images are captured at different exposures to create HDR image, then dynamic range is increased, but temporal disparity increases motion artifacts
Solution Approach 1:
The patent applies dynamics by making the image selection process adaptive rather than static. The system dynamically selects which exposure image to use for each pixel based on motion detection and analysis, allowing the system to adapt to motion conditions in real-time during the HDR synthesis process, thereby reducing motion artifacts while preserving dynamic range.
Solution Approach 2:
The patent applies local quality by treating different regions of the image differently based on their motion characteristics. Instead of uniformly selecting one exposure image for the entire scene, the system analyzes motion in local regions and selects the most appropriate exposure image for each pixel, allowing static regions to use any exposure while motion-affected regions use exposures that minimize artifacts.
2Object-generated harmful factors
If de-ghosting algorithm is applied to remove motion artifacts, then ghost reduction is achieved, but HDR image quality degrades due to exposure difference
Solution Approach 1:
The patent applies preliminary action by performing motion detection and exposure selection before the HDR synthesis process. By identifying motion-affected pixels and selecting appropriate exposure images in advance, the system prevents ghosting artifacts from being introduced during synthesis, eliminating the need for post-processing de-ghosting algorithms that would otherwise degrade image quality.
3Adaptability or versatility
If tone mapping is applied to convert HDR to LDR for display, then display compatibility is achieved, but local contrast is reduced
Solution Approach 1:
The patent applies local quality by implementing local tone mapping that preserves contrast in specific regions while maintaining overall display compatibility. The system identifies regions with important local contrast requirements and applies tone mapping parameters that preserve contrast in those regions, while applying more aggressive tone mapping in regions where it is less critical, thus maintaining both display compatibility and local contrast where needed.
Data Source
AI summary
A method and apparatus are provided for enhancing the local dynamic range of an image using the contents of exposure bracketed image set without affecting overall dynamic range of the image. The method allows a user to select at least one region of a reference image for enhancement after receiving the reference image from the user. Further the method comprises segmenting the reference image by using exposure weights, and selects an enhancement support image from an exposure bracketed image set. Furthermore the method determines weight maps of reference and enhancement support images and generates dynamic range enhanced reference image using determined weight maps.