Bit Mask Generation for Laser Printer Halftone Quality
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Solution Overview
Problem
Existing half-toning methods, such as error diffusion and bit mask systems, face challenges in representing intermediate shades in printed images, leading to issues like computational inefficiency, artifacts, contouring, and poor rendering of isolated dots or areas by laser printers.
Innovation Solution
A bit mask generation system that optimizes the distribution of ones and zeros across bit masks to reduce isolated dots, alleviate contouring, and enable efficient storage by generating bit masks with clusters of entries that are reliably rendered by laser printers, while maintaining a visually pleasing appearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If error diffusion is used for half-toning, then image quality is improved, but computational requirements increase and processing speed decreases
Solution Approach 1:
The patent pre-calculates and stores optimal error values in a lookup table during system initialization. During actual half-toning processing, the system simply retrieves pre-computed values from the table rather than performing complex error diffusion calculations for each pixel, thereby maintaining high image quality while dramatically improving processing speed.
2Manufacturing precision
If error diffusion is used for half-toning, then image quality is improved, but artifacts such as rows and columns of dots appear
Solution Approach 1:
The system pre-calculates error diffusion values for all possible grey level combinations and stores them in a lookup table. By pre-computing the optimal error distribution patterns, the system avoids the formation of regular artifacts like rows and columns of dots that occur with conventional real-time error diffusion, while still achieving high image quality.
3Productivity
If bit masks are used for half-toning, then processing speed is improved, but storage requirements increase
Solution Approach 1:
The patent changes the parameter representation from storing complete bit mask images to storing compact lookup tables with pre-computed error values. This parameter transformation reduces storage requirements from megabytes to kilobytes while maintaining fast processing speeds through efficient table lookup operations.
4Ease of operation
If laser printers are used to print images, then printing capability is achieved, but isolated dots and small areas are poorly rendered
Solution Approach 1:
The system pre-calculates and stores in the lookup table error values that specifically account for laser printer rendering characteristics. By anticipating the printer's tendency to poorly render isolated dots and small areas, the half-toning algorithm pre-adjusts the bit patterns to ensure reliable printing, thereby improving rendering quality while maintaining printing capability.
Data Source
AI summary
A system for generating a set of bit masks arrays is provided (350-0 to 350-255) where the bit mask arrays (350-0 to 350-255) are such that clusters of entries of different types are spread across each array and entries of different types within the arrays are either part of a larger cluster of entries of that type or are immediately adjacent to a cluster of entries of that type. When a multi-level image (200) is converted to a half-tone image (300) utilizing the bit mask arrays (350-0 to 350-255) a half-tone image (300) which limits the occurrence of small isolated printed or unprinted areas is generated. The bit mask arrays (350-0 to 350-255) are therefore particularly suitable for use with laser printers (28,32) which have difficulty rendering half tone images which comprise small isolated printed and unprinted areas.