Preserving Black Composition in Digital Printing Over Special Colors
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Solution Overview
Problem
In digital printing, preserving the black composition of objects overprinted on special colors results in reduced black values, leading to register errors and unreadable bar codes due to current color space transformation methods, which fail to maintain maximum black value accuracy.
Innovation Solution
A two-stage color transformation method where the special color and black object are processed separately, with the black proportion maximized in regions overprinted on special colors, ensuring a maximum black value is maintained in the CMYK process color space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a standard color space transformation is applied to convert black objects overprinted on special colors, then the color combination is calculated correctly according to colorimetric principles, but the black value is reduced below 100% causing register errors and unreadable bar codes
Solution Approach 1:
The patent applies different processing rules to different regions of the print image. Specifically, when a black object (with black value close to 100%) is detected to be overprinted on a special color, the system preserves the black value at 100% in that specific location, while other areas undergo standard color transformation. This local differentiation resolves the contradiction by maintaining black value stability where critical (on special colors) while preserving overall color accuracy.
Solution Approach 2:
The patent dynamically adjusts the black value parameter based on the underlying color. When the object color indicates a special color background, the black value is set to maximum (100%). Otherwise, standard color transformation rules apply. This parameter change strategy ensures that black objects maintain their required high contrast and readability when overprinting on special colors, while avoiding unnecessary deviations in other contexts.
2Reliability
If the black value is maximized to 100% for all black objects, then bar codes and high-contrast objects are preserved, but color accuracy is compromised in areas where black objects are not present
Solution Approach 1:
Rather than applying a global black value maximization, the patent uses local quality by detecting the specific color context beneath each black object. Only black objects overprinting on special colors receive the 100% black value treatment, while other regions maintain their colorimetrically accurate transformations. This selective approach preserves color accuracy in non-critical areas while ensuring reliability where needed.
3Manufacturing precision
If a two-stage transformation process is implemented to preserve black composition, then black value accuracy is maintained, but processing complexity increases
Solution Approach 1:
The patent segments the color transformation process into distinct stages: first identifying black objects with values close to 100%, then determining their underlying color, and finally applying conditional processing. This segmentation of the transformation workflow makes the complex process manageable and systematic, breaking down the overall task into discrete, controllable steps that can be implemented efficiently.
Solution Approach 2:
The patent performs preliminary identification and classification of black objects before executing the full color transformation. By pre-detecting which objects are black (close to 100% black value) and determining their spatial relationship to special colors, the system prepares the data structure needed for the conditional processing step. This preliminary action reduces the complexity of the subsequent transformation by pre-organizing the information needed for decision-making.
Data Source
AI summary
A method for preserving the black composition of at least one object positioned to overprint a special color in a print image for preprint color management of a printing operation using a computer, includes transforming the special color and the object into a combination of process colors of the printing operation during the color management process and then using this combination of process colors to generate the print image in a printing machine. The color transformation into the process colors of the printing operation is achieved in two stages. In a first stage, the color transformation into the process colors is carried out while keeping the special colors, then checking if the object is overprinted onto the special color, then removing the black proportion of the object and then in a second stage, transforming the special color into the process colors and subsequently maximizing the black proportion of the object.