Color Conversion Table Generation for Printer Reproducibility
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Solution Overview
Problem
Existing color conversion techniques require a long time to generate color conversion tables for converting signal values in a printer-independent color space to a printer-dependent color space, which affects color reproducibility.
Innovation Solution
A color conversion apparatus that generates a first color-conversion table describing the correspondence between input values in a printer-independent color space and colorimetric values, and uses this table along with a predetermined second color-conversion table to convert input signal values efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a color conversion table is generated by numerically solving conversion conditions based on colorimetric results, then color reproducibility is improved, but the time required for color conversion becomes long
Solution Approach 1:
The patent pre-calculates and stores color conversion tables (first color conversion table mapping input values to colorimetric values, and second color conversion table mapping colorimetric values to output signal values) before actual color conversion is needed. This preliminary preparation allows rapid color conversion during normal operation without performing time-consuming numerical solving at runtime, thus resolving the contradiction between achieving accurate color reproduction and maintaining fast conversion speed.
2Productivity
If colorimetric matching is not considered during conversion, then conversion speed is maintained, but color reproducibility of the printer is reduced
Solution Approach 1:
The patent performs colorimetric matching calculations in advance during table generation, not during real-time conversion. By pre-computing the first color conversion table that incorporates colorimetric value correspondences and the second color conversion table that maps to printer signal values, the system achieves both accurate color reproduction and fast conversion speed. The colorimetric matching is done once during table creation, then lookup operations are performed during actual conversion, eliminating the trade-off.
3Measurement precision
If numerical solving is performed to generate color conversion tables, then colorimetric accuracy is improved, but processing time increases
Solution Approach 1:
The patent performs the time-consuming numerical solving and colorimetric accuracy calculations during the table generation phase, not during actual color conversion. The first color conversion table stores the precise mapping between input values and colorimetric values, while the second color conversion table stores the mapping to output signal values. Once these tables are pre-computed with high accuracy, subsequent color conversion operations use simple table lookup, achieving both high measurement precision and fast processing.
Solution Approach 2:
The patent creates lookup tables that copy pre-calculated color conversion data into a format suitable for rapid retrieval. Instead of performing complex numerical solving during each conversion operation, the system uses pre-computed table data that replicates the accurate colorimetric relationships in a form that enables instant access during actual conversion, thus separating the computationally intensive table generation from the fast lookup operations.
Data Source
AI summary
A color conversion apparatus includes a processor configured to: generate a first color-conversion table describing a correspondence between an input value in a first color space and a colorimetric value in the first color space, the first color space being independent of a printer, the colorimetric value being a result of color measurement of a printed image obtained by the printer printing a signal value in a second color space, the second color space being dependent of the printer, the signal value in the second color space being a conversion result of the input value; and convert an input signal value in the first color space to a signal value in the second color space by using the first color-conversion table and a second color-conversion table, the second color-conversion table being predetermined in accordance with the printer and being used to convert a signal value in the first color space to a signal value in the second color space.