Digital Image Lighting Compensation Using Reference Maps
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Solution Overview
Problem
Digital images of surfaces, such as historical documents or paintings, often suffer from uneven lighting due to the reliance on ambient or flash lighting, which cannot be adequately corrected by existing methods.
Innovation Solution
A system that captures a reference lighting map under similar conditions to the digital image, inverts and overlays it to adjust the image, using color information to compensate for lighting inconsistencies, and can generate or select maps based on lighting models and surface characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a digital camera is used to capture images of surfaces, then portability and flexibility are improved, but lighting uniformity deteriorates due to reliance on ambient or flash lighting
Solution Approach 1:
The patent introduces a reference lighting map as an intermediary element that captures the lighting conditions of the scene. This map is then used to compensate for uneven lighting in the target image by comparing pixel values and adjusting colors accordingly, effectively mediating between the uneven ambient lighting and the desired uniform illumination appearance
Solution Approach 2:
The patent changes the parameters of the captured image by using the reference lighting map to adjust color values and brightness levels. The system modifies the RGB values of pixels based on the ratio between reference map values and target image values, thereby transforming the lighting characteristics from uneven to uniform
2Reliability
If existing lighting correction methods are used, then some lighting issues may be addressed, but effectiveness deteriorates when dealing with complex uneven lighting conditions
Solution Approach 1:
The patent performs preliminary action by capturing a reference lighting map under the same lighting conditions before or during the target image capture. This reference map pre-records the lighting pattern, enabling subsequent compensation without requiring complex real-time analysis of the target image's lighting conditions
Solution Approach 2:
The system uses feedback by comparing the target image pixels with corresponding pixels in the reference lighting map. The compensation process continuously adjusts color values based on the ratio between reference and target values, creating a closed-loop correction that adapts to the specific lighting conditions captured in the reference map
Data Source
AI summary
A system that compensates for uneven lighting in a digital image of a surface. During operation, the system receives the digital image of the surface. Next, the system obtains a reference lighting map for the surface, which contains information about the lighting of the surface at the time the digital image was acquired. The system then uses the reference lighting map to compensate for uneven lighting in the digital image.