Tile-Based Color Space Transformation for L*a*b* to CMYK Conversion
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Solution Overview
Problem
Color space transformations from L*a*b* to CMYK in digital copiers and multifunction devices are computationally expensive and time-consuming, affecting system performance and image quality.
Innovation Solution
A tile-type based color space transformation method that uses 1D look-up tables for neutral tiles and chrominance adjustment followed by tetrahedral interpolation for tiles with color content, reducing processing time and avoiding switching artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex color space transformation methods (e.g., tetrahedral interpolation) are used to convert from L*a*b* to CMYK, then color accuracy is improved, but processing time increases significantly
Solution Approach 1:
The image is divided into multiple tiles, and each tile is processed independently. Neutral tiles are identified and processed using fast 1D look-up tables, while color-containing tiles are processed using accurate but slower tetrahedral interpolation. This segmentation allows the system to apply different processing strategies to different regions, optimizing both speed and accuracy.
Solution Approach 2:
Different processing methods are applied to different regions of the image based on their color characteristics. Neutral regions (grayscale areas) use simple 1D look-up tables for fast processing, while color regions use complex tetrahedral interpolation for accurate color transformation. This local differentiation ensures that computational resources are focused only where needed.
2Productivity
If 1D look-up tables are used for color space transformation, then processing speed is improved, but color accuracy deteriorates
Solution Approach 1:
The processing method is dynamically selected based on the content of each tile. The system first analyzes each tile to determine whether it contains color information or is neutral. Based on this dynamic assessment, it switches between two processing modes: fast 1D look-up table conversion for neutral tiles and accurate tetrahedral interpolation for color tiles. This dynamic adaptation allows the system to optimize performance for each specific region.
3Productivity
If different transformation methods are used for neutral and color tiles, then processing efficiency is improved, but switching artifacts may occur
Solution Approach 1:
Before applying different transformation methods to neutral and color tiles, the system performs a preliminary chroma detection on each tile. This preliminary action identifies which tiles contain color information and which are neutral, allowing the system to pre-plan the processing strategy for each tile. Additionally, chroma adjustment is applied to neutral pixels in color tiles to ensure they are treated consistently, preventing switching artifacts at tile boundaries.
Data Source
AI summary
A system and method for tile type based color space transformation improves the performance and image quality of multifunction devices. The disclosed embodiments transform an input image on a tile by tile basis. If a tile is detected as neutral, simple 1D L* to CMYK Tone Reproduction Curves or Look-Up-Tables are used to convert the input pixels of the tile in L*a*b* to output pixels in CMYK. If a tile is detected as containing color content, then the input pixels are chrominance adjusted and subsequently converted to CMYK using regular tetrahedral interpolation.