Method and system for generating contone encoded binary print data streams

• US 7,580,569 B2
• Filed: 11/07/2005
• Issued: 08/25/2009
• Est. Priority Date: 11/07/2005
• Status: Expired due to Fees

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Nagarajan, Ramesh, Tse, Francis K.
• Primary Examiner(s): PERUNGAVOOR, SATHYANARAYA V
• Application Number:
  US11/268,147
• Publication Number:
  US 20070103731A1
• Time in Patent Office: 1,387 Days
• Field of Search: 382/180
• US Class Current: 382/180
• CPC Class Codes: H04N 1/4092 Edge or detail enhancement

Abstract

A method and system to convert an image described in a page description language to a contone image. The contone image is halftoned and encoded to generate image data including edge tag data and image data. A tagged state value of each pixel of image data within a predefined neighborhood of pixels is determined. The image data is filtered using a predetermined set of filter weighting values wherein each pixel of image data within the predefined neighborhood of pixels has an associated filter weighting value. A predetermined filtered image value is assigned to each pixel having a tagged state indicating an edge pixel. A summation of all filtered image values for the predefined neighborhood of pixels is assigned when the tagged state of the pixel is a non-edge pixel.

Claims

1. A method for converting a first pixel of image data to a first pixel of contone image data, comprising:

(a) electronically converting an image described in a page description language to a contone image;

(b) electronically halftoning and encoding the contone image to generate two bits of data;

(c) electronically determining a tagged state value for each pixel of a plurality of pixels of image data based upon the two bits of data and determining image data for a pixel based upon one of the two bits of data;

(d) electronically reconstructing a first pixel of image data to create reconstructed contone image data;

(e) electronically summing a plurality of tagged state value dependent weighted pixel values to create summed contone image data, each tagged state value dependent weighted pixel value corresponding to a pixel of image data within a predefined neighborhood of pixels of image data, the predefined neighborhood of pixels of image data having the first pixel of image data therein, a tagged state value dependent weighted pixel value being zero when the tagged state value of the corresponding pixel of image data indicates that the corresponding pixel of image data is an edge pixel and a tagged state value dependent weighted pixel value being equal to a product of a coefficient and a corresponding pixel value when the tagged state value of the corresponding pixel of image data indicates that the corresponding pixel of image data is a non-edge pixel;

(f) electronically selecting, when the tagged state value of the first pixel of image data indicates the first pixel of image data is a non-edge pixel, the summed contone image data as an image data value for the first pixel of contone image data; and

(g) electronically selecting, when the tagged state value of the first pixel of image data indicates the first pixel of image data is an edge pixel, the reconstructed contone image data as the image data value for the first pixel of contone image data.

2. The method as claimed in claim 1, wherein a tagged state value dependent weighted pixel value is equal to a product of a coefficient, a window coefficient, and a corresponding pixel value when the tagged state value of the corresponding pixel of image data indicates that the corresponding pixel of image data is a non-edge pixel, the window coefficient being equal to 1/n wherein n is a number pixels of image data within the predefined neighborhood of pixels having a tagged state value indicating that the pixel of image data is a non-edge pixel.

3. The method as claimed in claim 2, wherein each pixel of image data within the predefined neighborhood of pixels has an associated binary image value.

4. The method as claimed in claim 1, wherein a tagged state value dependent weighted pixel value is equal to a product of a coefficient, a window coefficient, and a corresponding pixel value when the tagged state value of the corresponding pixel of image data indicates that the corresponding pixel of image data is a non-edge pixel and each pixel position within the predefined neighborhood of pixels having a coefficient value assigned thereto, the window coefficient being equal to 1/S wherein S is a sum of all coefficient values within the predefined neighborhood of pixels.

5. The method as claimed in claim 4, wherein each pixel of image data within the predefined neighborhood of pixels has an associated binary image value.

6. The method as claimed in claim 1, further comprising:

(h) performing a tonal reproduction curve operation upon the selected image data value for the first pixel of contone image data when the tagged state value of the first pixel of image data indicates the first pixel of image data is a non-edge pixel.

7. The method as claimed in claim 1, wherein a tagged state value dependent weighted pixel value is equal to a product of a coefficient, a non-edge window coefficient, and a corresponding pixel value when the tagged state value of the corresponding pixel of image data indicates that the corresponding pixel of image data is a non-edge pixel and each pixel position within the predefined neighborhood of pixels having a coefficient value assigned thereto, the non-edge window coefficient being a value dependent upon a sum of all coefficients within the predefined neighborhood of pixels having a tagged state value of the corresponding pixel of image data indicating that the corresponding pixel of image data is a non-edge pixel.

8. The method as claimed in claim 1, wherein a tagged state value dependent weighted pixel value is equal to a product of a coefficient, an edge window coefficient, and a corresponding pixel value when the tagged state value of the corresponding pixel of image data indicates that the corresponding pixel of image data is a non-edge pixel and each pixel position within the predefined neighborhood of pixels having a coefficient value assigned thereto, the non-edge window coefficient being a value dependent upon a sum of all coefficients within the predefined neighborhood of pixels having a tagged state value of the corresponding pixel of image data indicating that the corresponding pixel of image data is an edge pixel.

9. The method of claim 1, wherein the determination of the tagged state value for each pixel of a plurality of pixels of image data is based upon a logical XOR operation of the two bits of data.

10. The method of claim 1, wherein the determination of the tagged state value for each pixel of a plurality of pixels of image data is based upon a logical NXOR operation of the two bits of data.

11. A system for converting a first pixel of image data to a first pixel of contone image data, comprising:

a conversion circuit to convert an image described in a page description language to a contone image;

an encoder circuit to halftone and encode the contone image data to generate two bits of data;

a conversion circuit to convert each pixel of two-bit data from said encoder circuit to edge tag data, having a tagged state value, based upon the two bits of data and image data based upon one of the two bits of data;

a reconstruction circuit to create reconstructed contone image data from a first pixel of image data;

a filtered summing circuit to sum a plurality of tagged state value dependent weighted pixel values to create summed contone image data, each tagged state value dependent weighted pixel value corresponding to a pixel of image data within a predefined neighborhood of pixels of image data, the predefined neighborhood of pixels of image data having the first pixel of image data therein, a tagged state value dependent weighted pixel value being zero when the tagged state value of the corresponding pixel of image data indicates that the corresponding pixel of image data is an edge pixel and a tagged state value dependent weighted pixel value being equal to a product of a coefficient and a corresponding pixel value when the tagged state value of the corresponding pixel of image data indicates that the corresponding pixel of image data is a non-edge pixel; and

a selection circuit, operatively connected to said filtered summing circuit and said reconstruction circuit, to select, when the tagged state value of the first pixel of image data indicates the first pixel of image data is a non-edge pixel, the summed contone image data as an image data value for the first pixel of contone image data and to select, when the tagged state value of the first pixel of image data indicates the first pixel of image data is an edge pixel, the reconstructed contone image data as the image data value for the first pixel of contone image data.

12. The system as claimed in claim 11, wherein a tagged state value dependent weighted pixel value is equal to a product of a coefficient, a window coefficient, and a corresponding pixel value when the tagged state value of the corresponding pixel of image data indicates that the corresponding pixel of image data is a non-edge pixel, the window coefficient being equal to 1/n wherein n is a number pixels of image data within the predefined neighborhood of pixels having a tagged state value indicating that the pixel of image data is a non-edge pixel.

13. The system as claimed in claim 11, wherein a tagged state value dependent weighted pixel value is equal to a product of a coefficient, a window coefficient, and a corresponding pixel value when the tagged state value of the corresponding pixel of image data indicates that the corresponding pixel of image data is a non-edge pixel and each pixel position within the predefined neighborhood of pixels having a coefficient value assigned thereto, the window coefficient being equal to 1/S wherein S is a sum of all coefficient values within the predefined neighborhood of pixels.

14. The system as claimed in claim 11, wherein a tagged state value dependent weighted pixel value is equal to a product of a coefficient, a non-edge window coefficient, and a corresponding pixel value when the tagged state value of the corresponding pixel of image data indicates that the corresponding pixel of image data is a non-edge pixel and each pixel position within the predefined neighborhood of pixels having a coefficient value assigned thereto, the non-edge window coefficient being a value dependent upon a sum of all coefficients within the predefined neighborhood of pixels having a tagged state value of the corresponding pixel of image data indicating that the corresponding pixel of image data is a non-edge pixel.

15. The system as claimed in claim 11, wherein a tagged state value dependent weighted pixel value is equal to a product of a coefficient, an edge window coefficient, and a corresponding pixel value when the tagged state value of the corresponding pixel of image data indicates that the corresponding pixel of image data is a non-edge pixel and each pixel position within the predefined neighborhood of pixels having a coefficient value assigned thereto, the non-edge window coefficient being a value dependent upon a sum of all coefficients within the predefined neighborhood of pixels having a tagged state value of the corresponding pixel of image data indicating that the corresponding pixel of image data is an edge pixel.

16. The system as claimed in claim 11, further comprising:

a tonal reproduction curve circuit, operatively connected to said filtered summing circuit, to perform a tonal reproduction curve operation upon the create summed contone image data to produce a corrected summed contone image data;

said selection circuit selecting, when the tag of the first pixel of image data indicates the first pixel of image data is a non-edge pixel, the corrected summed contone image data as an image data value for the first pixel of contone image data.

17. The system of claim 11, wherein said conversion circuit converts each pixel of two-bit data from said encoder circuit to edge tag data based upon a logical XOR operation of the two bits of data.

18. The system of claim 11, wherein said conversion circuit converts each pixel of two-bit data from said encoder circuit to edge tag data based upon a logical NXOR operation of the two bits of data.