Composite Image Luminance Mapping for SDR-HDR Range Matching
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Solution Overview
Problem
Existing methods fail to generate a composite image with different dynamic ranges effectively, particularly when compositing SDR and HDR images, leading to unnatural brightness on the high luminance side due to varying peak luminance in HDR images captured with different exposure amounts.
Innovation Solution
An image processing apparatus and method that converts the dynamic range of an SDR image to match the HDR image's range by determining a composition range based on the HDR image, using conversion units to adjust the SDR image's dynamic range to the HDR image's peak luminance, and then compositing them.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If SDR and HDR images are composited using conventional mapping methods, then a composite image can be generated, but unnatural brightness appears on the high luminance side due to varying peak luminance in HDR images
Solution Approach 1:
The patent changes the parameter of peak luminance mapping by establishing a correspondence relationship between SDR and HDR images based on their respective peak luminance values. Instead of using fixed mapping methods, the system dynamically adjusts the luminance range conversion by identifying the maximum luminance in the HDR image and the maximum displayable luminance in the SDR image, then creating a proportional mapping relationship that preserves natural luminance distribution across the composite image.
2Measurement precision
If HDR image peak luminance is used for mapping, then accurate luminance representation is achieved, but additional processing steps are required to determine peak luminance and establish correspondence
Solution Approach 1:
The patent applies preliminary action by performing peak luminance detection and correspondence relationship establishment before the actual compositing operation. The system first identifies the peak luminance values in both SDR and HDR images, establishes the mapping relationship between these peaks, and then uses this pre-established relationship to guide the subsequent compositing process, thereby simplifying the overall workflow.
3Speed
If simple compositing of SDR and HDR images is performed, then processing speed is maintained, but the composite image quality deteriorates due to dynamic range mismatch
Solution Approach 1:
The patent introduces an intermediary mapping relationship that acts as a bridge between SDR and HDR images. By establishing a correspondence based on peak luminance values, the system creates an intermediate representation that allows seamless integration of images with different dynamic ranges. This intermediary mapping enables efficient processing while maintaining high image quality, as it provides a straightforward conversion pathway without requiring complex real-time calculations during compositing.
Data Source
AI summary
An image processing apparatus acquires a first image and a second image having a dynamic range wider than a dynamic range of the first image, generates a converted image by converting the dynamic range of the first image, and generates a composite image by compositing the second image and the converted image. The apparatus decides a composition range based on the second image, and converts the dynamic range of the first image into the composition range.