Image rendering method and system using negative signals

1. A method of printing a digital image including:

receiving a stream of pixels representative of the digital image;

analyzing a set of the pixels for an image characteristic; and

based on the analyzing, assigning one of at least three different values to each pixel, wherein the three different values are selected from a set of values including at least one value representative of an attraction relative to a marking agent, at least one value representative of a repulsion relative to the marking agent, and at least one value representative of a neutrality relative to the marking agent.

2. The method of printing a digital image as set forth in claim 1 , where a particular assigned value indicates additional processing to be performed on a set of the stream of pixels, the method further comprising:

searching for the particular assigned value; and

based on the searching, performing the processing indicated by the particular assigned value.

3. The method of printing a digital image as set forth in claim 1 , where the analyzing includes template matching the stream of pixels to identify the image characteristic, the method further comprising:

assigning an overshoot value to a pixel on a border of the image characteristic.

4. The method of printing a digital image as set forth in claim 1 , where the analyzing includes halftoning the stream of pixels and comparing neighboring pixels to detect the image characteristic, the method further comprising:

assigning an overshoot value to a pixel adjacent to the detected image characteristic.

5. The method of printing a digital image as set forth in claim 1 , where the image characteristic comprises pixels rendered to compensate for spatial image variations induced by an imaging output device.

6. The method of printing a digital image as set forth in claim 1 , further including for each pixel, converting the assigned value to an associated electrostatic potential on a charge retentive surface.

7. The method of printing a digital image as set forth in claim 6 , where the image characteristic includes a boundary, the assigning comprising:

assigning a value representative of marking agent attraction to a pixel on one side of the boundary; and

assigning a value representative of marking agent repulsion to a pixel on an other side of the boundary, wherein opposing electrostatic potentials on the charge retentive surface sharpen the boundary of marking agent on the charge retentive surface.

8. The method of printing a digital image as set forth in claim 6 , where the converting comprises:

illuminating a portion of the charge retentive surface with a first writing device for assigned values representative of marking agent attraction; and

illuminating a portion of the charge retentive surface with a second writing device for assigned values representative of marking agent repulsion.

9. A charge on a charge retentive surface in a xerographic marking device, the charge comprising:

a positive charge, greater than an exposure bias, determined to electrostatically react with a charged monochrome marking agent in a first manner;

a negative charge, less than the exposure bias, determined to electrostatically react with the charged marking agent in a manner opposite the first manner and;

a super-negative charge, less than the negative charge which reacts with the marking agent in a manner opposite the first manner.

10. The charge on a charge retentive surface as set forth in claim 9 , further comprising a super-positive charge, greater than the positive charge, determined to electrostatically react with the charged marking agent in the first manner.

11. A xerographic marking device comprising:

a source of pixels representative of digitized image information;

a rendering image processor which analyzes the pixels for an image characteristic, and based on the analysis assigns one of at least three values to each pixel, wherein the three values are selected from a set of values including at least one value representing a positive relationship relative to a predetermined exposure bias, at least one value representing a negative relationship relative to the exposure bias, and at least one value representing a neutral relationship relative to the exposure bias; and

an imaging output device which converts the values assigned to the pixels into areas of selective exposure on a charge retentive surface.

12. The xerographic marking device as set forth in claim 11 , where the image characteristic indicates subsequent image processing to be performed on the pixel, the rendering image processor further comprising:

a processor which performs the subsequent image processing in response to receiving the pixel having the image characteristic.

13. The xerographic marking device as set forth in claim 11 , where the image characteristic comprises a compensation for variations attributable to an imaging output device, the processor further assigning values reflecting the compensation for the pixel.

14. The xerographic marking device as set forth in claim 11 , where the processor includes a template matching algorithm which identifies the image characteristic in the stream of pixels, the processor further assigning an overshoot value to a pixel bordering the identified image characteristic.

15. The xerographic marking device as set forth in claim 11 , where the processor includes a thresholding and error propagation algorithm, the processor further combining negative errors induced by thresholding and assigning a negative value representing the negative error.

16. The xerographic marking device as set forth in claim 11 , further comprising:

a super-positive charge on the photoreceptor in a location corresponding to the image characteristic, the super-positive charge electrostatically reacting with a marking agent in a first manner.

17. The xerographic marking device as set forth in claim 11 , further comprising:

a super-negative charge on the photoreceptor in a location corresponding to the image characteristic.

18. The xerographic marking device as set forth in claim 11 , further comprising:

a first charge altering writer having a first spot size which selectively alters a charge on a photoreceptor to electrostatically react with a marking agent in a first manner.

19. The xerographic marking device as set forth in claim 18 , further comprising:

a second charge altering writer having a second spot size which selectively alters the charge on the photoreceptor in other than the first manner.