Luminance Dynamic Range Expansion for Image Detail Preservation
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Solution Overview
Problem
Conventional display devices can only display images with a dynamic range of around 2 orders of magnitude, leading to loss of contrast and detail due to the conversion of high dynamic range images to a lower 8-bit luminance range, which does not consider image characteristics or human visual system properties, and may introduce artifacts.
Innovation Solution
A method to increase the dynamic range of an image by determining a background luminance value for each pixel, calculating a conversion factor based on minimum and maximum luminance values, and multiplying pixel luminance values by these factors to convert from a first luminance dynamic range to a second, higher range, using techniques like low pass filtering and color format transformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If linear scaling is used to increase dynamic range, then the dynamic range is enlarged, but image quality deteriorates due to artifacts and counteracting effects in gradually changing regions
Solution Approach 1:
The patent applies local quality by determining background luminance values for each pixel and calculating conversion factors specific to each pixel based on its local neighborhood. This allows different regions of the image to be scaled differently, preserving local characteristics and avoiding the uniform scaling artifacts that degrade image quality.
Solution Approach 2:
The patent performs preliminary action by first determining background luminance values through filtering operations before applying the dynamic range expansion. This preprocessing step captures the local image characteristics and enables the subsequent pixel-wise conversion to account for gradual changes, preventing artifact formation.
2Adaptability or versatility
If tone mapping is used to map high dynamic range to low dynamic range for display, then compatibility with conventional displays is maintained, but contrast and detail are lost
Solution Approach 1:
The patent inverts the conventional approach by instead of mapping high dynamic range to low dynamic range, it expands low dynamic range images to high dynamic range. This reverse process (LDR to HDR) allows preservation of contrast and detail while maintaining compatibility with HDR-capable displays, avoiding the information loss inherent in traditional tone mapping.
3Ease of manufacture
If conventional 8-bit luminance dynamic range is used, then compatibility with existing video and image formats is maintained, but the ability to utilize high dynamic range display capabilities is limited
Solution Approach 1:
The patent applies parameter changes by transforming the luminance dynamic range parameter from 8-bit to 12-bit. This parameter transformation enables the image to utilize the full capabilities of high dynamic range displays while maintaining compatibility with existing formats through the conversion process that respects original image characteristics.
Data Source
AI summary
A method of increasing the dynamic range of an image comprising a plurality of pixels each having a luminance value within a first luminance dynamic range. The method includes determining a background luminance value for each pixel of the image and determining a minimum and a maximum of the background luminance values. A conversion factor is then determined for each pixel of the image based on the minimum and maximum of the background luminance values. The image id converted from the first luminance dynamic range to a second luminance dynamic range by multiplying the luminance value of each pixel of the image by its conversion factor.