Self-timed two-dimensional filter

• US 5,751,862 A
• Filed: 05/08/1996
• Issued: 05/12/1998
• Est. Priority Date: 05/08/1996
• Status: Expired due to Term

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Schweid, Stuart A., Williams, Dawn M.
• Primary Examiner(s): Lee, Thomas D.
• Application Number:
  US08/643,427
• Time in Patent Office: 734 Days
• Field of Search: 382/260, 382/261, 382/262, 382/263, 382/264, 382/265, 382/254, 358/447, 358/448, 358/455, 358/456, 358/458
• US Class Current: 382/260
• CPC Class Codes: H03H 17/0202 Two or more dimensional filters; Filters for complex signals multidimensional convolutions G06F17/153
• CPC Class Codes: H04N 1/40062 Discrimination between different image types, e.g. two-tone, continuous tone
• CPC Class Codes: H04N 1/405 Halftoning, i.e. converting the picture signal of a continuous-tone original into a corresponding signal showing only two levels

Abstract

A filter for filtering digital image data includes a timing circuit to convert received line sync signal and a received page sync signal to a new line sync signal and a new page sync signal and a N×M filter to filter digital data based on the new line sync signal, the new video valid signal and the new page sync signal. N is a value representing a filter dimension in a slow scan direction, and M is a value representing a filter dimension in a fast scan direction. The timing circuit causes the self-timed image processing device to output (N-1)/2 scanlines of unfiltered digital image data after the received page sync signal indicates an end of an input page.

Claims

1. A self-timed image processing device for filtering digital image data, comprising:

a timing circuit to convert a received line sync signal and a received page sync signal to a new line sync signal and a new page sync signal; and

a N×

M filter to filter digital data based on said new line sync signal and said new page sync signal;

N being a value representing a filter dimension in a slow scan direction, M being a value representing a filter dimension in a fast scan direction;

said timing circuit causing the self-timed image processing device to output (N-1)/2 scanlines of unfiltered digital image data after the received page sync signal indicates an end of an input page.

2. The self-timed image processing device as claimed in claim 1, wherein said timing circuit causes the self-timed image processing device to output unfiltered digital image data after ((N-1)/2)+1 received line sync signals have been received and the received page sync signal indicates a beginning of an input page.

3. The self-timed image processing device as claimed in claim 2, wherein said timing circuit causes the self-timed image processing device to output filtered digital image data after N received line sync signals have been received and the received page sync signal indicates a beginning of an input page.

4. The self-timed image processing device as claimed in claim 1, further comprising:

a plurality of scanline buffers to buffer scanlines of digital image data prior to filtering.

5. A method for filtering digital image data, comprising the steps of:

(a) receiving line sync signals;

(b) receiving a page sync signal;

(c) receiving a plurality of scanlines of digital image data;

(d) filtering, using a N×

M filter, the received scanlines of digital image data and outputting filtered digital image data; and

(e) bypassing said step (d) when the received page sync signal indicates a beginning of an input page and ((N-1)/2)+1 line sync signals have been received.

6. The method as claimed in claim 5, further comprising the steps of:

(f) bypassing said steps (d) and outputting (N-1)/2 scanlines of unfiltered digital image data when the received page sync signal indicates an end of an input page.

7. The method as claimed in claim 6, further comprising the set of:

(g) bypassing said step (d) and outputting no digital image data when the received page sync signal indicates the beginning of the input page and before ((N-1)/2)+1 line sync signals have been received.

8. The method as claimed in claim 7, further comprising the step of:

(h) buffering the received plurality of scanlines of digital image data.

9. A filter, comprising:

a plurality of buffers to receive digital image data to be filtered; and

filter means for filtering the buffered digital image data and outputting the digital image data based on a state of a received page sync signal and received line sync signals;

said filter means filtering the buffered digital data and outputting filtered digital image data when the received page sync signal indicates an input page is being received and when N line sync signals have been received, N being a value representing a filter dimension in a slowcan direction;

said filter means bypasses the filtering operation and outputs unfiltered digital image data when the received page sync signal indicates when the input page is being received and when ((N-1)/2)+1 line sync signals have been received.

10. The filter as claimed in claim 9, wherein said filter means bypasses the filtering operation and outputs (N-1)/2 scanlines of unfiltered digital image data when the received page sync signal indicates an end of the input page.

11. The filter as claimed in claim 10, wherein said filter means bypasses the filtering operation and outputs no digital image data when the received page sync signal indicates when the input page is being received and before ((N-1)/2)+1 line sync signals are received.

12. A method for filtering comprising the steps of:

(a) buffering received digital image data;

(b) filtering the buffered digital data;

(c) outputting filtered digital image data when a received page sync signal indicates an input page is being received and when N line sync signals have been received, N being a value representing a filter dimension in a slowscan direction; and

(d) bypassing said steps (b) and (c) and outputting unfiltered digital image data when the received page sync signal indicates when the input page is being received and when ((N-1)/2)+1 line sync signals have been received.

13. The method as claimed in claim 12, further comprising the step of:

(e) bypassing said steps (b), (c), and (d) and outputting (N-1)/2 scanlines of unfiltered digital image data when the received page sync signal indicates an end of the input page.

14. The method as claimed in claim 13, further comprising the step of:

(f) bypassing said steps (b), (c), (d), and (e), and outputting no digital image data when the received page sync signal indicates when the input page is being received and before ((N-1)/2)+1 line sync signals are received.