Selective Halftone Smoothing for Text and Graphics

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Solution Overview

Problem

Conventional digital multifunction reprographic systems produce text and graphics with jagged edges due to halftoning, and struggle to smooth edges and maintain complex picture objects when using halftone patterns for both image paths, leading to suboptimal print quality.

Innovation Solution

The implementation of an image path with two parallel methods for rendering binary data into a frame buffer memory, using a high frequency checkerboard pattern to encode binary tile patterns, which are then decoded to restore the original halftone pattern and smooth edges, while preserving the intended shapes of objects and avoiding errors in edge positions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Shape

If a low frequency halftone screen (100-150 lines per inch) is used, then the shades appear smoother and more stable, but the edges become jagged and poorly formed

Engineering Contradiction:

Improveedge smoothnessVSAvoidedge definition

Core Design Contradiction:

ShapeVSManufacturing precision

Solution Approach 1:

The patent segments the halftoning process into two distinct paths: one for picture image data that preserves original halftone characteristics, and another for text/graphics data that applies encoding/decoding to smooth edges. This segmentation allows each path to be optimized independently for its specific requirements.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies different processing qualities to different regions of the image. Text and graphics objects receive edge smoothing treatment through encoding/decoding, while picture image data maintains its original halftone appearance. This local quality approach ensures that smoothing is applied only where needed without affecting other image regions.

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If a high frequency halftone screen is used, then the edges appear smoother, but the shades become less stable and the print quality deteriorates

Engineering Contradiction:

Improveedge definitionVSAvoidshade stability

Core Design Contradiction:

Manufacturing precisionVSShape

Solution Approach 1:

The patent introduces an intermediary encoding/decoding process that acts as a mediator between the halftone clusters and the final output. The encoding step adds a high frequency pattern that fills gaps between clusters, and the decoding step removes this pattern while preserving the smoothing effect, thereby bridging the gap between cluster separation and continuous edge appearance.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent performs preliminary encoding of the halftone pattern before final rendering. By pre-encoding the tile patterns with a high frequency checkerboard pattern and then decoding them during bitmap processing, the system prepares the edge smoothing information in advance, allowing the final output to achieve smooth edges without requiring high frequency halftone screens.

Inventive Principle:

Principle #10Preliminary action

3Adaptability or versatility

If halftone patterns are applied to both text/graphics and picture image data paths, then consistent processing is achieved, but text and graphics objects suffer from jagged edges and poor shape formation

Engineering Contradiction:

Improveprocessing consistencyVSAvoidobject shape quality

Core Design Contradiction:

Adaptability or versatilityVSShape

Solution Approach 1:

The patent implements a dynamic processing system that adapts the halftone application based on the type of data being processed. The system dynamically determines whether to apply encoding/decoding for text and graphics or to use direct halftoning for picture images, allowing the processing method to change according to the specific requirements of each data type rather than applying a static uniform approach.

Inventive Principle:

Principle #15Dynamics

4Reliability

If the gaps between halftone clusters are not bridged, then the original halftone pattern is preserved, but the edges of text and graphics remain jagged and poorly formed

Engineering Contradiction:

Improvehalftone pattern integrityVSAvoidedge smoothness

Core Design Contradiction:

ReliabilityVSShape

Solution Approach 1:

The patent temporarily discards the original halftone pattern information during the encoding step by overlaying a high frequency checkerboard pattern, then recovers the essential edge information during decoding by removing the encoded pattern while preserving the smoothed edge appearance. This discarding and recovering process allows the system to transform the jagged cluster-based pattern into a smooth continuous edge while maintaining the fundamental halftone structure.

Inventive Principle:

Principle #34Discarding and recovering

Data Source

PatentUS8368959B2Method and system for selective smoothing of halftoned objects using bitmap encoding

Publication Date: 2013.02.05 XEROX CORP

AI summary

An image processing system utilizes an image type classification circuit to identify inputted image data as picture image data or text/graphics image data. A halftone circuit, operatively connected to the image type classification circuit, converts the inputted image data, identified as picture image data, to halftone image data. Moreover, a tile pattern circuit, operatively connected to the image type classification circuit, to replace the inputted image data, identified as text/graphics image data, with tile patterns. Non-halftone cluster areas in the tile patterns are encoded with a predetermined pattern. A bitmap rendering circuit combines the halftone image data with the encoded tile patterns to render a bitmap, wherein the bitmap can be used by a print engine to reproduce the image.