Method and an apparatus for generating a video binary signal for a video image having a matrix of pixels

• US 5,189,710 A
• Filed: 09/17/1990
• Issued: 02/23/1993
• Est. Priority Date: 09/17/1990
• Status: Expired due to Term

• Current Assignee: Rocket Software Incorporated
• Original Assignee: Teknekron Communications Systems Incorporated
• Inventors: Holt, Kenneth C.
• Primary Examiner(s): Moore, David K.
• Application Number:
  US07/583,444
• Time in Patent Office: 890 Days
• Field of Search: 382/22, 382/50, 382/52, 358/99
• US Class Current: 382/273
• CPC Class Codes: H04N 1/403 Discrimination between the two tones in the picture signal of a two-tone original

Abstract

In the present invention, a method and an apparatus for dynamically setting a discrimination threshold for the processing of an image is disclosed. The image is composed of a matrix of pixels with each pixel having a grey scale value. The pixels are arranged in a plurality of lines with each line having a plurality of pixels. The plurality of pixels are supplied to a line buffers memory. From the line buffers memory, the white peak line and the black minimum line are supplied to a peak and minimum detectors which determine the white peak value and the black minimum value associated with an edge. The white peak value and the black minimum values are stored. The stored white peak and black minimum values are supplied to a threshold calculator to which a user selectable input is also supplied. The output of a threshold calculator is a threshold level which is used by comparator. Another input to the comparator is the grey scale value of the pixel from the image. The output of the comparator is a binary video signal.

Claims

1. An apparatus for dynamically setting a discrimination threshold for the processing of an image having one or more edges said image is composed of a plurality of lines, each having a plurality of pixels, each pixel having a grey value, said apparatus comprising:

means for receiving a plurality of said lines of pixels;

means for determining the pixel ("instantaneous maximum pixel") having the maximum grey value among the plurality of pixels received;

means for receiving said instantaneous maximum pixel and for storing its grey value in the event said instantaneous maximum pixel is associated with one of said edges of said image;

means for determining the pixel ("instantaneous minimum pixel") having the minimum grey value among the plurality of pixels received;

means for receiving said instantaneous minimum pixel and for storing its grey value in the event said instantaneous minimum pixel is associated with one of said edges of said image;

means for setting a grey scale threshold based upon the stored minimum grey value and the stored maximum grey value; and

means for comparing the grey value of each pixel of said image to said grey scale threshold to produce a first binary output for each pixel.

2. The apparatus of claim 1 wherein said setting means is responsive to a user selectable input to set the grey scale threshold between the stored minimum grey value and the stored maximum grey value based upon said user selectable input.

3. The apparatus of claim 2 wherein said setting means further comprises:

means for subtracting the stored minimum grey value from the stored maximum grey value to produce a difference value;

means for multiplying said difference value by said user selectable input expressed as a percentage to produce an intermediate value; and

means for summing said intermediate value to said stored minimum grey value to produce said grey scale threshold.

4. The apparatus of claim 1 further comprising means for delaying said pixels prior to being supplied to said comparing means.

5. The apparatus of claim 1 further comprising means for filtering said pixels prior to being supplied to the determining means.

6. The apparatus of claim 1 further comprising:

means for generating a high frequency binary output for each pixel;

means for receiving said first binary output and said high frequency binary output; and

means for detecting an edge and for switching the output of said apparatus between said first binary output and said high frequency binary output, in response to said edge detected.

7. The apparatus of claim 6 wherein said means for detecting an edge further comprises:

a plurality of different types of edge detecting means, each for generating an output upon the detecting of an edge different from the other;

means for receiving the plurality of outputs from the different types of edge detecting means;

said receiving means also responsive to a user selectable input for switching the output of said apparatus in response to said user selectable input selecting one of said type of edge detecting means.

8. A method of generating a video binary signal for a video image having one or more edges, said image having a plurality of lines each having a plurality of pixels with each pixel having a grey scale value, said method comprising:

receiving a plurality of lines of pixels;

determining the first pixel having the maximum grey value among the plurality of pixels received;

storing the maximum grey value determined in the event the first pixel determined is associated with one of said edges of said image;

determining the second pixel having the minimum grey value among the plurality of pixels received;

storing the minimum grey value determined in the event the second pixel determined is associated with one of said edges of said image;

setting a grey scale threshold based upon the stored minimum grey value and the stored maximum grey value; and

comparing the grey value of each pixel of said video image to said grey scale threshold to produce said video binary signal.

9. The method of claim 8 wherein said setting step further comprises the steps of:

receiving a user input; and

generating the grey scale threshold between the stored minimum grey value and the stored maximum grey value based upon the user input.

10. The method of claim 9 wherein said generating step further comprising:

subtracting the stored minimum grey value from the stored maximum grey value to produce a difference value;

multiplying said difference value by said user selectable input expressed as a percentage to produce an intermediate value; and

summing said intermediate value to said stored minimum grey value to produce said grey scale threshold.

11. The method of claim 8 further comprising:

delaying the pixels of the image prior to the comparing step.

12. The method of claim 8 further comprising:

filtering the pixels prior to the determining step.

13. The method of claim 8 further comprising:

generating a high frequency binary output signal for each pixel;

receiving the video binary signal and the high frequency binary output signal by a combiner;

detecting an edge in said image; and

switching the output of the combiner between the video binary signal and the high frequency binary output signal in response to the edge detected in the image.

14. An apparatus for dynamically setting a discrimination threshold for the processing of an image having one or more edges, said image is composed of a plurality of lines, each having a plurality of pixels, each pixel having a grey value, said apparatus comprising:

means for receiving a plurality of said lines of pixels;

first means for detecting an edge of said image among the plurality of said lines of pixels;

first means for determining the maximum grey value of the pixels in the region of said edge detected;

second means for determining the minimum grey value of the pixels in the region of said edge detected;

means for storing said minimum and maximum grey values;

means for setting a grey scale threshold based upon the stored minimum grey value and the stored maximum grey value; and

means for comparing the grey value of each pixel of said image to said grey scale threshold to produce a first binary output for each pixel.

15. The apparatus of claim 14 further comprising:

means for generating a high frequency binary output for each pixel;

means for receiving said first binary output and said high frequency binary output; and

second means for detecting an edge and for switching the output of said apparatus between said first binary output and said high frequency binary output in response to said edge detected by said second detecting means.

16. The apparatus of claim 15 wherein said second means for detecting an edge further comprises:

a plurality of different types of edge detecting means, each for generating an output upon the detecting of an edge different from the other; and

means for receiving the plurality of outputs from the different types of edge detecting means;

said receiving means responsive to a user selectable input for switching the output of said apparatus in response to said user selectable input selecting one of said type of edge detecting means.

17. The apparatus of claim 14 wherein said edge detected has a first side having light grey values associated therewith, and a second side, having dark grey values associated therewith.

18. The apparatus of claim 17 wherein said first determining means determines the maximum grey value of the pixels on said first side and said second determining means determines the minimum grey value of the pixels on said second side.

19. The apparatus of claim 14 wherein said setting means comprises a plurality of different means for calculating said grey scale threshold and wherein said setting means is further responsive to a user selectable input to select one of said calculating means to calculate said grey scale threshold.