Dithering Based Color Conversion for Thermal Printers
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Solution Overview
Problem
Existing thermal printing technologies face challenges in mathematically interpolating discrete 3D LUT values for color conversion, particularly when dealing with thermal photo paper, as each node contains a unique pulse pattern, making linear combination of non-linearly combinable output nodes difficult.
Innovation Solution
Implementing halftone dithering for multi-dimensional look-up-table (LUT) output nodes using interpolation techniques like tri-linear and tetrahedral interpolation, where weights are interpreted as probabilities to determine the likelihood of each node being printed, ensuring accurate color representation and dot distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If discrete 3D LUT values are used for color conversion in thermal printing, then color space conversion is achieved, but mathematical interpolation of output nodes becomes difficult due to unique pulse patterns at each node
Solution Approach 1:
The patent introduces dithering as an intermediary technique between the discrete 3D LUT and the thermal printing process. By using dithering matrices with probabilistic threshold values, the system enables mathematical interpolation of LUT output nodes without directly combining their unique pulse patterns. The dithering process acts as a mediator that translates the discrete node selections into printable dot patterns, resolving the interpolation difficulty while preserving color conversion accuracy.
Solution Approach 2:
The patent changes the parameter representation from direct pulse pattern combination to probabilistic dot distribution. Instead of attempting to mathematically combine the unique pulse patterns at each LUT node, the system transforms the problem into selecting nodes based on interpolated weights and then using dithering to probabilistically distribute dots. This parameter transformation makes the interpolation process feasible while maintaining color fidelity.
2Adaptability or versatility
If linear combination of LUT output nodes is attempted, then intermediate colors can be represented, but the unique pulse patterns at each node make non-linear combination difficult
Solution Approach 1:
The patent replaces the mechanical approach of directly combining pulse patterns with a computational dithering system. Instead of attempting to physically or mathematically merge the unique pulse patterns from multiple LUT nodes, the system uses algorithmic dithering to probabilistically select and distribute dots corresponding to each node. This substitution of mechanical combination with computational probability simplifies the processing while enabling versatile color representation.
3Manufacturing precision
If dithering is applied to interpret weights as probabilities, then intermediate colors are accurately represented, but dot distribution control becomes more complex
Solution Approach 1:
The patent applies preliminary dithering processing to the LUT output weights before they are used to control dot distribution. By pre-calculating the dithered threshold values and comparing them against the interpolated weights, the system determines dot placement probabilities in advance. This preliminary action simplifies the real-time control complexity while achieving precise color fidelity through the probabilistic dot distribution.
Data Source
AI summary
In some examples, dithering based color conversion may include ascertaining an input color value. Based on conversion of the input color value to an output color space representation, a set of nodes that are to be analyzed to control operation of a printer may be determined. Based on a position of the input color value from each node of the set of nodes, a corresponding probability associated with each node of the set of nodes may be determined. Further, the operation of the printer may be controlled based on the determined probability associated with each node of the set of nodes.