Method and system for extending binary image data to contone image data

• US 20060257045A1
• Filed: 05/11/2005
• Published: 11/16/2006
• Est. Priority Date: 05/11/2005
• Status: Active Grant

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: McCandlish, Peter D.
• Granted Patent: US 7,787,703 B2
• Time in Patent Office: Days
• US Class Current: 382/261
• CPC Class Codes: G06T 2207/20192 Edge enhancement; Edge preservation
• CPC Class Codes: G06T 5/003 Deblurring; Sharpening vibration or motion blur correction for cameras comprising an electronic image sensor H04N23/682
• CPC Class Codes: G06T 5/20 using local operators
• CPC Class Codes: G06T 5/73 Deblurring; Sharpening
• CPC Class Codes: G06T 7/12 Edge-based segmentation
• CPC Class Codes: H04N 1/4092 Edge or detail enhancement

Abstract

A method and system converts a binary image into an analog image by first tagging pixels that are part of edges in the digital image and using this tagging information to eliminate such tagged pixels from the digital filtering process. The elimination of such tagged pixels from the digital filtering process substantially eliminates artifacts near the edges, thereby reducing any distraction from the perceived quality of the output image.

Claims

1. A method for converting edge-tagged pixels of image data to pixels of contone image data, comprising:

(a) determining a tagged state value of each pixel of image data within a predefined neighborhood of pixels, each pixel of image data within the predefined neighborhood of pixels having an associated image value, a first pixel of image data within the predefined neighborhood of pixels being associated a first pixel of contone image data;

(b) filtering, 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, each image value of each pixel 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 to generate a filtered image value for each pixel 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;

(c) assigning, a predetermined filtered image value to each pixel of image data within the predefined neighborhood of pixels having a tagged state value indicating that the pixel of image data is an edge pixel;

(d) summing all filtered image values for the predefined neighborhood of pixels to produce an image data sum value; and

(e) assigning, 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 image data sum value as an image data value for the first pixel of contone image data.

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

(f) assigning, when the tagged state value of the first pixel of image data indicates the first pixel of image data is an edge pixel, the image data value of the first pixel of image data as an image data value for the first pixel of contone image data.

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

(f) determining a number, N, 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;

(g) modifying, when the tagged state value of the first pixel of image data indicates the first pixel of image data is a non-edge pixel, 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, such that each filter weighting value associated with 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 is equal to 1/N and each filter weighting value associated with pixels of image data within the predefined neighborhood of pixels having a tagged state value indicating that the pixel of image data is an edge pixel is equal to 0; and

(h) modifying, when the tagged state value of the first pixel of image data indicates the first pixel of image data is an edge pixel, the predetermined set of filter weighting values such that the filter weighting value associated with the first pixel of image data is equal to 1 and each filter weighting value associated with a non-first pixel of image data within the predefined neighborhood of pixels is equal to 0;

wherein said filtering-uses the modified set of filter weighting values upon each pixel of image data within the predefined neighborhood of pixels to generate a filtered image value for each pixel of image data within the predefined neighborhood of pixels.

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

5. The method as claimed in claim 4, wherein said summing only sums filter weighting values that are associated with pixels within the predefined neighborhood of pixels having an image value indicating a non-zero intensity value to produce an image data sum value.

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

(f) determining a sum, S, of all filter weighting values within the predetermined set of filter weighting values associated with 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;

(g) modifying, when the tagged state value of the first pixel of image data indicates the first pixel of image data is a non-edge pixel, 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, such that each filter weighting value associated with 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 is equal to a product of the predetermined filter weighting value and 1/S and each filter weighting value associated with pixels of image data within the predefined neighborhood of pixels having a tagged state value indicating that the pixel of image data is an edge pixel is equal to 0; and

(h) modifying, when the tagged state value of the first pixel of image data indicates the first pixel of image data is an edge pixel, the predetermined set of filter weighting values such that the filter weighting value associated with the first pixel of image data is equal to 1 and each filter weighting value associated with a non-first pixel of image data within the predefined neighborhood of pixels is equal to 0;

wherein said filtering uses the modified set of filter weighting values upon each pixel of image data within the predefined neighborhood of pixels to generate a filtered image value for each pixel of image data within the predefined neighborhood of pixels.

7. The method as claimed in claim 6, wherein each pixel of image data within the predefined neighborhood of pixels has an associated binary image value.

8. The method as claimed in claim 7, wherein said summing only sums filter weighting values that are associated with pixels within the predefined neighborhood of pixels having an image value indicating a non-zero intensity value to produce an image data sum value.

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

(f) performing a tonal reproduction curve operation upon the assigned image data value for the first pixel of contone image data.

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

(f) producing a sum of predetermined filter weights for 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;

(g) applying the sum as an input to a lookup table; and

(h) using an output of the lookup table, corresponding to inputted sum, to modify the predetermined filter weights for 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.

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

(f) producing a sum of predetermined filter weights for pixels of image data within the predefined neighborhood of pixels having a tagged state value indicating that the pixel of image data is an edge pixel;

(g) applying the sum as an input to a lookup table; and

(h) using an output of the lookup table, corresponding to inputted sum, to modify the predetermined filter weights for 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.

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

(f) producing a sum of predetermined filter weights for 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;

(g) applying the sum as an input to a lookup table; and

(h) multiplying the image data sum value by an output value from the lookup table, corresponding to inputted sum to modify the image data sum value.

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

(f) producing a sum of predetermined filter weights for pixels of image data within the predefined neighborhood of pixels having a tagged state value indicating that the pixel of image data is an edge pixel;

(g) applying the sum as an input to a lookup table; and

(h) multiplying the image data sum value by an output value from the lookup table, corresponding to inputted sum to modify the image data sum value.

14. A system for converting edge-tagged pixels of image data to pixels of contone image data, comprising:

a selection circuit to determine a tagged state value of each pixel of image data within a predefined neighborhood of pixels, each pixel of image data within the predefined neighborhood of pixels having an associated image value, a first pixel of image data within the predefined neighborhood of pixels being associated a first pixel of contone image data;

a filter circuit to filter, 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, each image value of each pixel 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 to generate a filtered image value for each pixel 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; and

said selection circuit selecting a predetermined filtered image value for each pixel of image data within the predefined neighborhood of pixels having a tagged state value indicating that the pixel of image data is an edge pixel;

said selection circuit selecting said filtered image value from said filter circuit for each pixel 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;

an accumulator to sum all filtered image values for the predefined neighborhood of pixels to produce an image data sum value.

15. The system as claimed in claim 14, further comprising:

a filter weight modifier circuit to determine a tagged state value of each pixel of image data within a predefined neighborhood of pixels, each pixel of image data within the predefined neighborhood of pixels having an associated image value, a first pixel of image data within the predefined neighborhood of pixels being associated a first pixel of contone image data; and

said filter weight modifier circuit determining a number, N, 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;

said filter weight modifier circuit modifying, when the tagged state value of the first pixel of image data indicates the first pixel of image data is a non-edge pixel, 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, such that each filter weighting value associated with 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 is equal to 1/N and each filter weighting value associated with pixels of image data within the predefined neighborhood of pixels having a tagged state value indicating that the pixel of image data is an edge pixel is equal to 0;

said filter weight modifier circuit modifying, when the tagged state value of the first pixel of image data indicates the first pixel of image data is an edge pixel, the predetermined set of filter weighting values such that the filter weighting value associated with the first pixel of image data is equal to 1 and each filter weighting value associated with a non-first pixel of image data within the predefined neighborhood of pixels is equal to 0;

said filter circuit filtering, using the modified set of filter weighting values, each pixel of image data within the predefined neighborhood of pixels, to generate a filtered image value for each pixel of image data within the predefined neighborhood of pixels and to sum all filtered image values for the predefined neighborhood of pixels to produce an image data sum value an image data value for the first pixel of contone image data.

16. The system as claimed in claim 14, further comprising:

a filter weight modifier circuit to determine a tagged state value of each pixel of image data within a predefined neighborhood of pixels, each pixel of image data within the predefined neighborhood of pixels having an associated image value, a first pixel of image data within the predefined neighborhood of pixels being associated a first pixel of contone image data; and

said filter weight modifier circuit determining a sum, S, of all filter weighting values within the predetermined set of filter weighting values associated with 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;

said filter weight modifier circuit modifying, when the tagged state value of the first pixel of image data indicates the first pixel of image data is a non-edge pixel, 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, such that each filter weighting value associated with 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 is equal to a product of the predetermined filter weighting value and 1/S and each filter weighting value associated with pixels of image data within the predefined neighborhood of pixels having a tagged state value indicating that the pixel of image data is an edge pixel is equal to 0;

said filter weight modifier circuit modifying, when the tagged state value of the first pixel of image data indicates the first pixel of image data is an edge pixel, the predetermined set of filter weighting values such that the filter weighting value associated with the first pixel of image data is equal to I and each filter weighting value associated with a non-first pixel of image data within the predefined neighborhood of pixels is equal to 0;

said filter circuit filtering, using the modified set of filter weighting values, each pixel of image data within the predefined neighborhood of pixels, to generate a filtered image value for each pixel of image data within the predefined neighborhood of pixels and to sum all filtered image values for the predefined neighborhood of pixels to produce an image data sum value as an image data value for the first pixel of contone image data.

17. The system as claimed in claim 14, further comprising:

a filter weight modifier circuit to determine a tagged state value of each pixel of image data within a predefined neighborhood of pixels, each pixel of image data within the predefined neighborhood of pixels having an associated image value, a first pixel of image data within the predefined neighborhood of pixels being associated a first pixel of contone image data; and

said filter weight modifier circuit determining a number, N, 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;

said filter weight modifier circuit modifying, when the tagged state value of the first pixel of image data indicates the first pixel of image data is a non-edge pixel, 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, such that each filter weighting value associated with 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 is equal to 1/N and each filter weighting value associated with pixels of image data within the predefined neighborhood of pixels having a tagged state value indicating that the pixel of image data is an edge pixel is equal to 0;

said filter weight modifier circuit modifying, when the tagged state value of the first pixel of image data indicates the first pixel of image data is an edge pixel, the predetermined set of filter weighting values such that the filter weighting value associated with the first pixel of image data is equal to 1 and each filter weighting value associated with a non-first pixel of image data within the predefined neighborhood of pixels is equal to 0;

said filter circuit filtering, using the modified set of filter weighting values, each pixel of image data within the predefined neighborhood of pixels, to generate a filtered image value for each pixel of image data within the predefined neighborhood of pixels and to sum, only filter weighting values that are associated with pixels within the predefined neighborhood of pixels having an image value indicating a non-zero intensity value, to produce an image data sum value as an image data value for the first pixel of contone image data.

18. The system as claimed in claim 14, further comprising:

a filter weight modifier circuit to determine a tagged state value of each pixel of image data within a predefined neighborhood of pixels, each pixel of image data within the predefined neighborhood of pixels having an associated image value, a first pixel of image data within the predefined neighborhood of pixels being associated a first pixel of contone image data; and

said filter weight modifier circuit determining a sum, S, of all filter weighting values within the predetermined set of filter weighting values associated with 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;

said filter weight modifier circuit modifying, when the tagged state value of the first pixel of image data indicates the first pixel of image data is a non-edge pixel, 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, such that each filter weighting value associated with 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 is equal to a product of the predetermined filter weighting value and 1/S and each filter weighting value associated with pixels of image data within the predefined neighborhood of pixels having a tagged state value indicating that the pixel of image data is an edge pixel is equal to 0;

said filter weight modifier circuit modifying, when the tagged state value of the first pixel of image data indicates the first pixel of image data is an edge pixel, the predetermined set of filter weighting values such that the filter weighting value associated with the first pixel of image data is equal to 1 and each filter weighting value associated with a non-first pixel of image data within the predefined neighborhood of pixels is equal to 0;

said filter circuit filtering, using the modified set of filter weighting values, each pixel of image data within the predefined neighborhood of pixels, to generate a filtered image value for each pixel of image data within the predefined neighborhood of pixels and to sum, only filter weighting values that are associated with pixels within the predefined neighborhood of pixels having an image value indicating a non-zero intensity value, to produce an image data sum value as an image data value for the first pixel of contone image data.

19. The system as claimed in claim 14, further comprising:

a tonal reproduction curve circuit to perform a tonal reproduction curve operation upon the produced image data sum value.