Color Chart Generation for Camera Spectral Inference
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Solution Overview
Problem
Existing techniques for aligning colors between different camera models using 3D LUTs face challenges in accurately inferring spectral characteristics, particularly when using commercial color charts, leading to varying prediction accuracy.
Innovation Solution
An image processing apparatus and method for generating a color chart with specifically selected color patches to minimize the evaluation value E, calculated based on spectral reflectances, ensuring high accuracy in inferring camera spectral characteristics by optimizing the combination of color patch materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a commercial color chart is used to infer spectral characteristics of a camera, then the color chart is easy to obtain and use, but the prediction accuracy of spectral characteristics varies greatly
Solution Approach 1:
The patent applies local quality by customizing the spectral characteristics of individual color patches within the color chart. Instead of using uniform commercial color charts, each color patch is designed with specific spectral reflectance properties to target particular wavelength ranges, thereby improving the overall prediction accuracy while maintaining the chart's usability.
Solution Approach 2:
The patent changes the spectral parameters of the color patches by selecting materials with specific spectral reflectance characteristics. The evaluation value E, which quantifies the mismatch between actual and predicted spectral characteristics, is minimized by adjusting these parameters, thus achieving high prediction accuracy without sacrificing ease of use.
2Measurement precision
If color patches are selected to minimize evaluation value E, then the accuracy of spectral characteristic inference is improved, but the complexity of selecting and designing the color chart increases
Solution Approach 1:
The patent implements feedback by calculating the evaluation value E to quantify the accuracy of spectral characteristic inference. This feedback mechanism guides the selection of color patches, allowing iterative optimization to minimize E while managing the design complexity through a systematic approach.
Solution Approach 2:
The patent manages design complexity by changing the selection parameters of color patches based on their spectral reflectance characteristics. By optimizing these parameters to minimize E, the system achieves high inference accuracy while keeping the design process manageable through structured parameter adjustment.
3Productivity
If a 3D LUT is generated without imaging the color chart at the shooting location, then the workflow is simplified and time is saved, but the accuracy of color alignment may be compromised
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the spectral characteristics of color patches in the color chart before actual use. This allows the 3D LUT to be generated in advance with high accuracy, eliminating the need for on-site imaging while maintaining color alignment precision through the pre-computed spectral data.
Data Source
AI summary
An image processing apparatus can include an obtaining unit configured to obtain spectral reflectances of a plurality of color patches, and a control unit configured to generate design data of a color chart including a plurality of color patches selected so as to reduce an evaluation value E of the color chart calculated based on Equation (I) from the spectral reflectances of the plurality of color patches. (Rm, Rn: a spectral reflectance of a color patch whose index number is m, n; N: the number of color patches in the color chart; Σ: a sum of all combinations of m and n)