HDR Image Rendering Motion Analysis and Tone Mapping
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Solution Overview
Problem
Current technologies for generating and rendering high dynamic range (HDR) images face challenges in accurately representing the wide luminance range of natural scenes, as most devices can only handle limited dynamic ranges, leading to artifacts like block, banding, and ringing artifacts during compression and processing.
Innovation Solution
An HDR image generating system performs motion analysis on lower dynamic range (LDR) images to derive relative exposure levels, integrates these images to form an HDR image, and uses tone mapping to convert HDR images to LDR values, while allowing user preference adjustments for rendering parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If HDR images are processed and compressed to reduce file size, then storage and transmission costs decrease, but block, banding, and ringing artifacts are introduced that degrade image quality
Solution Approach 1:
The patent applies preprocessing operations before compression to mitigate artifacts. Specifically, it performs adaptive filtering to smooth block artifacts, applies dithering to prevent banding artifacts by adding noise to quantization errors, and uses deconvolution filtering to reduce ringing artifacts. These preliminary actions prepare the HDR image data in a way that minimizes the introduction of compression artifacts during subsequent encoding.
Solution Approach 2:
The patent dynamically adjusts compression parameters based on local image characteristics. It varies the compression strength and filtering parameters across different regions of the image, applying stronger smoothing in gradient regions prone to block artifacts and adjusting quantization levels to prevent banding. This adaptive parameter adjustment maintains image quality while achieving efficient compression.
2Manufacturing precision
If multiple LDR images are integrated to form HDR image, then dynamic range and image quality improve, but motion artifacts and misalignment occur when scene or camera moves
Solution Approach 1:
The patent performs motion estimation and compensation before integrating the LDR images. It analyzes motion between frames and applies appropriate transformations to align corresponding features across images with different exposures. This preliminary alignment ensures that when images are integrated, features from different exposure levels correspond to the same spatial locations, preventing misalignment artifacts and maintaining registration accuracy even when scene or camera motion occurs.
3Adaptability or versatility
If tone mapping is applied to convert HDR to LDR, then compatibility with standard devices is achieved, but detail and contrast information is lost
Solution Approach 1:
The patent applies local tone mapping that preserves detail and contrast in different regions of the image. Instead of applying a uniform tone mapping across the entire image, it adapts the tone mapping parameters locally based on regional characteristics such as brightness, contrast, and texture. This allows bright regions to be compressed differently from dark regions, preserving local details and contrasts while achieving overall compatibility with standard LDR display devices.
Data Source
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AI summary
Techniques and tools for high dynamic range (HDR) image rendering and generation. An HDR image generating system performs motion analysis on a set of lower dynamic range (LDR) images and derives relative exposure levels for the images based on information obtained in the motion analysis. These relative exposure levels are used when integrating the LDR images to form an HDR image. An HDR image rendering system tone maps sample values in an HDR image to a respective lower dynamic range value, and calculates local contrast values. Residual signals are derived based on local contrast, and sample values for an LDR image are calculated based on the tone-mapped sample values and the residual signals. User preference information can be used during various stages of HDR image generation or rendering.