Image Signal Processing Apparatus Tone Conversion
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Solution Overview
Problem
Existing image signal processing techniques face challenges in maintaining image quality, particularly in high and low luminance regions, where tone conversion can lead to whiteout or blackout, degrading the image quality due to variations in tone width and bit number during digital image processing.
Innovation Solution
An image signal processing apparatus and program that perform a combination of space-variant tone conversion and space-invariant tone correction processes, synthesizing the results to maintain tone characteristics in high luminance regions while extending tone reproduction in low and middle luminance regions, using synthesis rates adjusted based on luminance thresholds and areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If space-variant tone conversion is performed to extend tone width in certain luminance regions, then tone reproduction is improved in those regions, but whiteout occurs in high luminance regions or blackout occurs in low luminance regions
Solution Approach 1:
The patent applies different tone conversion characteristics to different luminance regions. Specifically, it performs space-variant tone conversion on low and middle luminance regions to extend tone width, while applying space-invariant tone conversion to high luminance regions to prevent whiteout. This local differentiation of processing strategies resolves the contradiction by optimizing each region according to its specific characteristics.
Solution Approach 2:
The patent segments the image into multiple luminance regions (high, middle, and low luminance regions) and applies different tone conversion processes to each segment. By dividing the image processing into region-specific operations, it prevents the harmful effects of uniform tone conversion while maintaining the benefits of extended tone width where appropriate.
2Manufacturing precision
If multiple tone conversion processes are performed to prevent whiteout and blackout, then image quality is improved, but processing complexity and power consumption increase
Solution Approach 1:
The patent dynamically adjusts the tone conversion strategy based on the luminance characteristics of different regions. It uses luminance threshold values to determine which regions require space-variant processing and which require space-invariant processing. This dynamic adaptation allows the system to achieve high image quality while avoiding the constant overhead of applying complex processing to all regions.
Solution Approach 2:
The patent changes the processing parameters (space-variant vs. space-invariant tone conversion) based on luminance region classification. By adjusting the conversion characteristics according to luminance levels, it achieves optimal image quality across different regions while managing processing complexity through parameter-based differentiation rather than structurally complex systems.
3Manufacturing precision
If tone conversion extends tone width in low luminance regions, then tone reproduction is enhanced, but processing time and computational load increase
Solution Approach 1:
The patent applies partial action by performing space-variant tone conversion only on low and middle luminance regions where it is most beneficial, rather than applying it to the entire image. This selective approach extends tone width where needed while reducing the overall computational load and processing time compared to full-image space-variant processing.
Data Source
AI summary
An image signal processing apparatus including a first tone correcting section for generating a first image signal by performing a space-variant tone conversion process for a digitalized image signal from a CCD and an A/D converting section, a second tone correcting section for generating a second image signal by performing a space-invariant tone correction process for the digitalized image signal from the CCD and the A/D converting section, and a synthesizing section for setting a synthesis rate R1 of the first image signal and a synthesis rate R2 of the second image signal, and synthesizing the first image signal and the second image signal based on the set synthesis rates R1 and R2.