Digital Image Light Direction Determination via Histogram Analysis
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Solution Overview
Problem
Digital cameras face challenges in determining the direction of external light, which affects image quality, due to the limitations of low-resolution liquid crystal display screens used in live-view modes, making it difficult for users to assess proper illumination.
Innovation Solution
A method and apparatus that process digital image signals by generating histograms for divided subject regions to analyze light direction, using comparisons of gray scale differences, averages, and luminance to determine if the light is side lighting, front/back lighting, or other types, allowing for improved illumination assessment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a low-resolution liquid crystal display screen is used for live-view mode, then the device complexity is reduced, but the measurement precision of light direction is insufficient
Solution Approach 1:
The patent introduces an intermediary processing system that analyzes image histograms and luminance values to determine light direction. Instead of relying on the display screen resolution, the system uses computational analysis of image data as a mediator between the captured image and the light direction determination, thereby achieving accurate measurement without requiring high-resolution display hardware.
Solution Approach 2:
The patent replaces the mechanical/physical limitation of display screen resolution with an information processing approach. By substituting the visual inspection method (which depends on display resolution) with automated histogram analysis and luminance comparison, the system achieves precise light direction determination independent of display hardware capabilities.
2Measurement precision
If the subject region is divided into multiple regions and histograms are generated, then the light direction determination accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the subject region into multiple sub-regions (e.g., left and right halves of the face) and generating separate histograms for each segment. This segmentation allows the system to detect luminance differences across different areas, which is crucial for determining light direction. The segmented approach provides more detailed information than analyzing the entire subject region as a whole.
Solution Approach 2:
The patent implements local quality analysis by examining the histogram characteristics and luminance values of specific local regions rather than treating the subject uniformly. By focusing on local luminance differences (e.g., which side of the face is brighter), the system can accurately determine light direction. This local analysis approach provides targeted insights without requiring complex processing of the entire image.
Data Source
AI summary
Provided are a method and apparatus for processing a digital image signal, and a recording medium having recorded thereon the method, in which an image including a subject is generated, a subject region is formed by detecting the subject from the image, the subject region is divided into at least two regions, histograms for the at least two regions are generated, respectively, and it is determined whether a light direction is side lighting by analyzing the histograms for the at least two regions.