Automatic image segmentation with smoothing

• US 5,327,262 A
• Filed: 05/24/1993
• Issued: 07/05/1994
• Est. Priority Date: 05/24/1993
• Status: Expired due to Term

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Williams, Leon C.
• Primary Examiner(s): BRINICH, STEPHEN M
• Application Number:
  US08/076,651
• Time in Patent Office: 407 Days
• Field of Search: 358/530, 358/462, 358/464, 358/538, 358/467, 382/51, 382/9, 382/50
• US Class Current: 358/462
• CPC Class Codes: G06T 5/30 Erosion or dilatation, e.g. thinning
• CPC Class Codes: H04N 1/40062 Discrimination between different image types, e.g. two-tone, continuous tone

Abstract

In conjunction with an image segmentation arrangement, in which the image is processed with an image type detection arrangement, the output of which controls an image processing of the image, there is provided a morphological filtering operation, which initially provides a noise removal filter operating on the image detection signal, to remove noise within an area of the image detection signal, and subsequently provides hole filling filter, which bridges small gaps in the image type detection results.

Claims

1. In a digital image processing system providing circuits for processing a digital image in accordance with one of a plurality of image types in accordance with an image type detection signal received at an image processing controller, a method for improving uniformity in image type detection, the steps comprising:

receiving from an image source a document image represented in a digital image signal format, having an unknown combination of the image types in the document image, and storing digital image signals representing an area of the document image in a data buffer;

with an image segmentation circuit, receiving digital image signals from the data buffer and determining image types present in an area of the document image therefrom, said image segmentation circuit producing a detection signal for each digital image signal representing the image type at a corresponding location within the image;

converting the detection signals into a plurality of binary signals, each binary signal representing detection or non detection of a single image type;

for binary detection signals of a single image type, providing a first filter processing said binary detection signals to provide a first state thereof whenever all the binary detection signals in a predetermined set thereof have a first state, and producing a first filtered binary detection signal indicative thereof;

for each binary detection signal of a single image type, providing a second filter, processing said first filtered binary detection signal to provide a first state thereof whenever any of the first filtered binary detection signals in a predetermined set thereof have a first state and producing a second filtered binary detection signal;

directing said second binary filtered detection signals to the image processing controller to control the circuits for processing plural image types in accordance with the determined image type.

2. The method as described in claim 1, where the image types include low frequency halftones, high frequency halftones, lines and text, and continuous tones.

3. The method as described in claim 1, where each detection signal represents an image type including one of low frequency halftones, high frequency halftones, lines and text, and continuous tones.

4. The method as described in claim 3, wherein the step of converting each detection signal into a plurality of binary signals, converts each detection signal into four binary signals, each representing detection or non detection of a single image type.

5. The method of claim 1, wherein the first and second filters are operative on a structuring element including a predetermined neighborhood of pixels.

6. The method of claim 5, wherein the structuring element differs between at least two image types.

7. The method as described in claim 1, wherein the predetermined set of binary detection signals includes a binary detection signal to be processed and a plurality of binary detection signals, together corresponding to a first predetermined area of the document image.

8. The method as described in claim 1, wherein the predetermined set of first filtered binary detection signals includes a first filtered binary detection signal to be processed and a plurality of first filtered binary detection signals, together corresponding to a second predetermined area of the document image.

9. The method as described in claim 1, wherein the image processing controller is responsive to a digital detection signal representing a combination of image type detection signals, and including the further step of:

combining the second binary filtered detection signal for each image type into a processed image type detection signal.

10. The method as described in claim 9, and including the step of:

comparing each processed image type detection signal with a set of valid signal quantities to determine if the signal is valid, and repeating the last valid signal if the signal is determined invalid.

11. A digital image processing system for controlling the processing of digital images in accordance with detected image types, comprising:

a buffer memory for receiving and storing at least a portion of the document image represented in a digital image signal format, having an unknown combination of the image types in the document image from an image source;

a plurality of image processing circuits, each processing the digital image for a particular image type;

an image processing controller producing a control signal controlling the output of said plurality of image processing circuits in accordance with the detected image type;

an image segmentation circuit, receiving digital image signals from the data buffer, and detecting image types present in an area of the document image, and producing a detection signal for each digital image signal representing a detected image type at a corresponding location within the image;

means for converting the detection signals into a plurality of binary signals representing detection or non detection of a single image type;

a first filter, receiving binary detection signals from said converting means and processing the binary detection signals to provide a first state thereof whenever all the binary detection signals in a predetermined set thereof have a first state, and producing a first filtered binary detection signal indicative thereof.

12. The device as described in claim 11, where the image types include low frequency halftones, high frequency halftones, lines and text, and continuous tones.

13. The device as described in claim 11, where each detection signal represents an image type including one of low frequency halftones, high frequency halftones, lines and text, and continuous tones.

14. The device as described in claim 13, wherein the means for converting each detection signal into a plurality of binary signals, converts each detection signal into four binary signals, each representing detection or non detection of a single image type.

15. The device as described in claim 11, wherein the first and second filters are operative on a structuring element including a predetermined neighborhood of pixels.

16. The device as described in claim 15, wherein the structuring element differs between at least two image types.

17. The device as described in claim 11, wherein the predetermined set of binary detection signals includes a binary detection signal to be processed and a plurality of binary detection signals, together corresponding to a first predetermined area of the document image.

18. The device as described in claim 11, wherein the predetermined set of first filtered binary detection signals includes a first filtered binary detection signal to be processed and a plurality of first filtered binary detection signals, together corresponding to a second predetermined area of the document image.

19. The device as described in claim 11, wherein the image processing controller is responsive to a digital detection signal representing a combination of image type detection signals, and further including:

means for combining the second binary filtered detection signal for each image type into a processed image type detection signal.

20. The device as described in claim 19, and further including:

means for comparing each processed image type detection signal with a set of valid signal quantities stored in a memory device functionally connected thereto, to determine if the signal is valid, and repeating the last valid signal if the signal is determined invalid;

a second filter, receiving said first filtered binary detection signals from said first filter and processing the first filtered binary detectio signals to provide a first state thereof whenever any of the first filtered binary detection signals in a predetermined set thereof have a first state and producing a second filtered binary detection signal;

said second filter functionally connected to the image processing controller and directing to the image processing controller the second filtered binary detection signal as an indication of the detected image type.