HDR-SDR Image Compositing With Peak Luminance Matching
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Solution Overview
Problem
Existing methods fail to generate a composite image with a preferable form when compositing images with different dynamic ranges, particularly due to varying peak luminance in High Dynamic Range (HDR) images captured with different exposure amounts, leading to unnatural brightness on High Dynamic Range (HDR) displays.
Innovation Solution
An image processing apparatus and method that converts the dynamic range of a Standard Dynamic Range (SDR) image to match that of a High Dynamic Range (HDR) image based on the HDR's peak luminance, using a conversion unit to generate a composite image by compositing the converted SDR image with the HDR image, ensuring a natural and harmonious display on HDR devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If SDR images are composited directly without dynamic range conversion, then the compositing process is simple and fast, but the composite image appears unnatural on HDR displays due to luminance range mismatch
Solution Approach 1:
The patent applies parameter changes by converting the dynamic range parameter of SDR images to match HDR image parameters. The conversion unit transforms pixel values from SDR luminance range to HDR luminance range using transfer functions (EOTF/OTF), thereby resolving the luminance accuracy issue while maintaining efficient compositing operations.
2Adaptability or versatility
If HDR images with different exposure amounts are composited, then the composite image can represent diverse luminance ranges, but the varying peak luminance causes unnatural brightness on HDR displays
Solution Approach 1:
The patent applies preliminary action by performing tone mapping conversion on HDR images with different exposure amounts before compositing. The conversion unit adjusts the peak luminance of each HDR image to a reference level, ensuring consistent brightness characteristics across all images before they are composited together.
Solution Approach 2:
The patent changes the peak luminance parameter of HDR images through tone mapping conversion. By transforming the luminance distribution of images with different exposure amounts to a standardized range, the system maintains adaptability to diverse scenes while ensuring consistent peak luminance for natural display appearance.
3Manufacturing precision
If SDR images are converted to HDR luminance range, then the composite image can be displayed naturally on HDR devices, but the conversion process increases processing complexity
Solution Approach 1:
The patent introduces an intermediary conversion unit that handles the complex task of SDR to HDR luminance range conversion. This dedicated unit uses established transfer functions (EOTF for encoding, OTF for decoding) to bridge the luminance gap between SDR and HDR images, managing the complexity centrally rather than distributing it throughout the system.
4Manufacturing precision
If tone mapping conversion is applied to HDR images, then the peak luminance can be standardized for natural display, but the conversion time increases processing duration
Solution Approach 1:
The patent applies partial action by implementing tone mapping conversion selectively rather than universally. The conversion unit processes only those HDR images that require peak luminance standardization (i.e., images with different exposure amounts), while leaving images already within the target luminance range unchanged, thereby reducing unnecessary processing time.
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.