Dynamic Color Shading Correction for Wide-Angle Lenses
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Solution Overview
Problem
Existing methods for correcting color shading artifacts in digital images are complex, computationally expensive, and fail to accurately address distortions in scenes with multiple illuminants or varying surface reflectances, particularly in compact cameras with wide-angle lenses, due to their reliance on pre-calibrated correction tables and white balance algorithms.
Innovation Solution
A dynamic color shading correction method that estimates color shading on the fly from scene statistics, separating the shading component from actual image content using gradient domain characteristics, and updates a pre-calibrated correction table to compensate for color non-uniformity, regardless of the scene illuminant or surface reflectances, without relying on white balance detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If per-unit calibration with pre-calculated correction tables is used, then color shading correction can be applied, but the method becomes complex, computationally expensive, and fails to accurately correct color shading in scenes with multiple illuminants or varying surface reflectances
Solution Approach 1:
The patent transforms the static pre-calibrated correction table into a dynamic correction mechanism that adapts to different illuminants and surface reflectances in real-time. The system estimates color shading profiles from actual image data and dynamically updates correction tables during image capture, allowing the correction method to adapt to varying lighting conditions and scene content without requiring complex per-unit calibration procedures.
Solution Approach 2:
The system performs self-calibration by automatically estimating color shading profiles from the captured image data itself, without requiring external calibration equipment or manual intervention. The color shading estimation module processes the captured image to derive correction information, enabling the system to correct its own color shading artifacts using the actual scene data.
2Adaptability or versatility
If white balance algorithms are used to detect scene illuminant, then color shading correction can be performed, but the method fails in scenes with multiple illuminants or objects having varying wavelength reflection
Solution Approach 1:
The patent segments the color shading correction process into distinct functional modules: a color shading estimation module that analyzes the captured image to identify color shading patterns, a correction table update module that generates updated correction tables based on the estimation, and a color shading correction module that applies the corrections. This segmentation allows each module to specialize in specific tasks, improving the system's ability to handle complex lighting conditions.
Solution Approach 2:
The system implements a feedback loop where the color shading estimation module continuously monitors the captured image data, estimates color shading profiles, and feeds this information back to update the correction tables. This feedback mechanism enables the system to adapt to changing lighting conditions and scene content in real-time, improving reliability in scenes with multiple illuminants or varying surface reflectances.
3Productivity
If pre-calibrated correction tables are used, then the correction method is simpler, but it cannot accurately correct color shading in real-time for varying scene conditions
Solution Approach 1:
The system performs preliminary color shading estimation by processing a downsampled version of the captured image to create a corrected downsampled image. This preliminary action prepares correction data in advance, which is then used to generate updated correction tables that are applied to the full-resolution captured image, enabling real-time correction while maintaining precision.
Data Source
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AI summary
Certain embodiments relate to systems and methods for dynamic color shading correction, which can estimate the color shading in a captured image on the fly. The color shading may be estimated from the scene statistics of the captured image, and the estimated shading may be used for color shading correction. The color shading estimation method may separate out the color shading component from the actual image content by its unique characteristic in the gradient domain.