Grayscale Conversion Apparatus for Toner Reduction and Discriminability
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Solution Overview
Problem
Existing grayscale conversion methods for printing color images as monochrome struggle to maintain discriminability between different gray levels, often resulting in increased toner usage due to close gray signal values after conversion, making it difficult for users to distinguish between various grays.
Innovation Solution
An image processing apparatus that converts color data into grayscale by generating gray targets with specific brightness values, ensuring a fixed difference between them, thereby maintaining discriminability while reducing toner consumption by assigning higher luminance values to certain colors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional grayscale conversion methods (e.g., NTSC) are used to convert color image data to grayscale, then the conversion process is simple and fast, but multiple different colors may become the same or close gray signal values making it difficult for users to discriminate between different levels of gray
Solution Approach 1:
The patent changes the conversion parameters by introducing a discrimination threshold and dynamically adjusting gray signal value assignments. Instead of using fixed NTSC weights, the system calculates minimum discriminable gray signal value differences based on human visual perception thresholds, ensuring that converted grayscale values maintain sufficient contrast for user discrimination while preserving conversion efficiency.
Solution Approach 2:
The patent implements dynamic adjustment of gray signal values based on the specific color distribution in the input image. The system analyzes the range of colors present and adaptively assigns gray signal values to ensure discriminability, rather than applying a static conversion formula. This dynamic approach maintains both speed and discrimination quality.
2Device complexity
If grayscale conversion is performed with uniform gray density assignment based on color count, then the conversion process is simplified, but the lightest gray becomes darker than the lowest discriminable gray from white increasing toner consumption
Solution Approach 1:
The patent optimizes the gray signal value parameters by establishing a minimum threshold (e.g., 10 in 256-level grayscale) for the lightest gray that is still discriminable from white. This parameter optimization ensures that converted images use the brightest possible grays that remain visually distinguishable, thereby minimizing toner consumption while maintaining perceived quality.
Solution Approach 2:
The patent applies partial action by selectively adjusting only the necessary gray levels rather than uniformly processing all grayscale values. By focusing optimization on the lightest grays that contribute most to toner consumption, the system achieves significant toner savings without requiring complete reprocessing of the entire grayscale range.
3Productivity
If multiple colors in color image data are converted using standard grayscale conversion, then the conversion is efficient, but the resulting gray signal values are often the same or close making color discrimination difficult
Solution Approach 1:
The patent introduces an intermediary processing step that analyzes the input color distribution and determines optimal gray signal value assignments before final conversion. This intermediary analysis layer acts as a mediator between the efficient but lossy standard conversion and the quality requirement for discrimination, enabling both efficiency and discrimination by pre-calculating optimal mappings based on the specific image content.
Data Source
AI summary
An image processing is configured to convert a color of a first object into gray having first brightness and a color of a second object into gray having second brightness lower than the first brightness by a fixed value in response to receiving color data including the first object and the second object, and output gray data based on the first brightness of gray into which the color of the first object is converted and the second brightness of gray into which the color of the second object is converted.