Adaptive image enhancement filter

• US 6,834,124 B1
• Filed: 10/16/2000
• Issued: 12/21/2004
• Est. Priority Date: 10/16/2000
• Status: Expired due to Term

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Loce, Robert P., Lin, Ying-wei
• Primary Examiner(s): AHMED, SAMIR ANWAR
• Application Number:
  US09/687,111
• Time in Patent Office: 1,527 Days
• Field of Search: 382/260, 382/261, 382/266, 382/254, 382/256, 333/156-212, 359/885-892, 455/213, 455/286, 455/307, 455/339, 708/300, 348/606, 348/610, 348/619-624, 358/1.2, 358/1.9, 358/3.27, 358/3.24
• US Class Current: 382/261
• CPC Class Codes: G06T 5/00 Image enhancement or restoration
• CPC Class Codes: H04N 1/40 Picture signal circuits H04N1/387 takes precedence

Abstract

An adaptive image enhancement filter includes a template matching module for comparing an observed pixel pattern comprising a target pixel and one or more neighboring pixels to a set of templates to determine if the observed pixel pattern matches any of the templates. The template matching module generates a match identifier signal indicating which of the templates, if any, the observed pixel pattern is found to match. Based on this match identifier, a signal generation module provides an enhanced output signal for the target pixel. The template matching and/or the signal generation modules can be independently modified to adapt to changing conditions as identified by signals identifying image attributes and marking process attributes.

Claims

1. An adaptive image enhancement filter for receiving image data including a plurality of pixels and generating enhanced image data for driving a marking engine for each pixel within the image data, comprising:

a template matching processor receiving an observation pattern including a target pixel and at least one pixel neighboring the target pixel, the template matching module comparing the observation pattern to a set of templates and generating a match identification signal; and

a signal generation processor connected to receive the match identification signal and a marking process attribute signal, the signal generation processor including a plurality of sets of optimized signals, each set of optimized signals containing a plurality enhanced signals for driving the marking engine, the signal generation processor identifying one of the sets of optimized signals in response to the marking engine attribute signal and providing in response to the received match identification an enhanced signal from the identified set of optimized signals signal as enhanced image data for the target pixel.

2. The adaptive image enhancement filter of claim 1, wherein the marking process attribute signal identifies at least one of the attributes including type of marking process, nature of the marking process, identification of the photoreceptor, reproduction of line width and density, corner reproduction, jaggie reproduction, overlay printing, output maximum density, lead edge and trail edge performance characteristics, responsiveness to small high addressable events, and change in responsiveness in terms of output density.

3. The adaptive image enhancement filter of claim 1, wherein the signal generation processor is further responsive to an image attribute signal when identifying one of the sets of optimized signals.

4. The adaptive image enhancement filter of claim 1, wherein each set of optimized signals comprises a lookup table.

5. The adaptive image enhancement filter of claim 1, wherein:

the signal generation processor further includes a selection processor; and

each set of optimized signals receives the match identification signal and provides a corresponding enhanced signal to the selection processor.

6. The adaptive image enhancement filter of claim 1, further comprising

a template storage device storing a plurality of template sets, each template set including a plurality of templates wherein each template is designed to identify a specific image structure to be enhanced;

and

wherein the template matching processor is further responsive to at least one of an image attribute signal and a marking process attribute signal to identify one of the plurality of template sets to which the received observation pattern is compared.

7. The adaptive image enhancement filter of claim 6, wherein the image attribute signal identifies at least one of the attributes including image resolution, pixel type and image classification.

8. The adaptive image enhancement filter of claim 6, wherein the template matching processor is responsive to at least one of the attributes including image resolution, pixel type, image classification, reproduction of line width and density, corner reproduction, jaggie reproduction, overlay printing, output maximum density, lead edge and trail edge performance and noise characteristics.

9. A method of generating enhanced image data for driving a marking engine, comprising:

receiving a set of pixels to be printed, the set of pixels including an observation window identifying a target pixel and at least one neighboring pixel;

comparing the pixels within the observation window to a set of pixel templates;

generating a template match identifier in response to the comparing step;

selecting one of a plurality of sets of optimized drive signals, each set of optimized drive signals containing a plurality enhanced signals for driving the marking engine; and

using the match identifier select one of enhanced signals from the selected set of optimized drive signals as the enhanced image data.

10. The method of claim 9, further comprising receiving a marking process attribute signal;

wherein the step of selecting one of a plurality of sets of optimized drive signals is in response to the marking process attribute signal.

11. The method of claim 10, further comprising receiving an image attribute signal.

12. The method of claim 11, wherein the step of selecting one of a plurality of sets of optimized drive signals is further responsive to the image attribute signal.

13. The method of claim 11, further comprising:

selecting the set of pixel templates from a plurality of template sets based on the image attribute signal.

14. The method of claim 9, further comprising:

receiving an image attribute signal; and

selecting the set of pixel templates from a plurality of template sets based on the image attribute signal.

15. The method of claim 9, wherein the step of selecting one of a plurality of sets of optimized drive signals selects a set that compensates for a marking process characteristic.

16. The method of claim 15, wherein the step of selecting one of a plurality of sets of optimized drive signals compensates for at least one characteristic from the set of attributes including type of marking process, nature of the marking process, identification of the photoreceptor, reproduction of line width and density, output maximum density, lead edge and trail edge performance characteristics, responsiveness to small high addressable events, a change in responsiveness in output density and a change in responsiveness in output width.