Color Error Diffusion with Dot-Gain Correction for Halftone Output
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Solution Overview
Problem
Existing color-image output devices face challenges in producing pleasing halftone images due to device-dependent color variations and dot gain issues, which affect the quality of printed output.
Innovation Solution
A unique color error diffusion process that converts input color data to a device-dependent halftone palette, prioritizing chrominance values based on quadrant-related arithmetic signage, followed by an intensity correction using a dot-gain correction curve to minimize output device-specific color discrepancies and dot gain problems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional color error diffusion is used without device-specific optimization, then the process is simple and fast, but the output image quality suffers from device-dependent color variations and dot gain issues
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing device-specific color lookup tables (LUTs) that map input color values to optimal output color values for the specific output device. This pre-computed mapping accounts for device characteristics and dot gain behavior, allowing the color diffusion process to reference these tables during image processing rather than calculating device corrections in real-time, thus improving output quality while managing complexity
Solution Approach 2:
The patent changes parameters by introducing device-specific color space transformation parameters and dot gain correction factors that are determined through characterization of the output device. These parameters are embedded in the color diffusion algorithm to adjust color values and dot sizes according to the specific device's behavior, resolving the contradiction between maintaining simple processing and achieving device-optimized output quality
2Manufacturing precision
If device-dependent color palettes are used to improve color accuracy, then output color fidelity improves, but the system becomes less adaptable to different output devices
Solution Approach 1:
The patent uses parameter changes by implementing a configurable color space transformation framework where the color diffusion algorithm can accept different device-specific parameters (color matrices, lookup tables, dot gain curves). This allows the same base algorithm to be adapted to different output devices by changing these parameters rather than rewriting the core diffusion logic, thus maintaining both color fidelity and device compatibility
Solution Approach 2:
The patent applies universality by designing a universal color diffusion framework that can handle multiple color spaces (RGB, CMYK, Lab) and multiple output device types through a common interface. The device-specific color palettes are integrated as optional parameters within this universal framework, allowing the system to maintain high color fidelity for each device type while preserving adaptability across different devices through the unified architecture
Data Source
AI summary
An improved color-image error diffusion process for use in conjunction with the operation of a multi-level, halftone, color-image output device. This process involves, first, performing output-device-dependent color error diffusion on color-image input data utilizing a halftone, output-device-dependent color palette containing output-device-dependent output color values. Thereafter, and with respect to the selection for pixel outputting of a pixel utilizing one of the output colors in the palette, and in relation to infeeding of that pixel to the output device for outputting, the process features applying a predetermined, dot-gain correction curve which corrects the infeed intensity value of the pixel in accordance with (a) the selected output color for the pixel, and (b) assessment of the pixel in terms of its association with a predetermined neighborhood pattern of adjacent pixels.