Image processing method and image processing device

• US 5,764,813 A
• Filed: 06/07/1995
• Issued: 06/09/1998
• Est. Priority Date: 07/25/1994
• Status: Expired due to Term

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Kuwata, Naoki, Aoki, Mikio, Murayama, Yasuhiko
• Primary Examiner(s): Bost, Dwayne
• Assistant Examiner(s): JOHNSON, BRIAN
• Application Number:
  US08/480,869
• Time in Patent Office: 1,098 Days
• Field of Search: 382/260, 382/261, 382/270, 382/271, 382/272, 382/273, 382/275, 382/112, 382/254, 382/176, 382/309, 358/401, 358/405, 358/406, 358/462, 358/465, 358/466
• US Class Current: 382/271
• CPC Class Codes: G06T 2207/10008 from scanner, fax or copier
• CPC Class Codes: G06T 2207/20021 Dividing image into blocks, subimages or windows
• CPC Class Codes: G06T 2207/30144 Printing quality
• CPC Class Codes: G06T 2207/30176 Document
• CPC Class Codes: G06T 5/70 Denoising; Smoothing
• CPC Class Codes: G06T 5/77 Retouching; Inpainting; Scratch removal
• CPC Class Codes: G06T 7/0002 Inspection of images, e.g. flaw detection
• CPC Class Codes: G06T 7/11 Region-based segmentation
• CPC Class Codes: G06T 7/136 involving thresholding
• CPC Class Codes: G06T 7/168 involving transform domain methods
• CPC Class Codes: G06V 30/10 Character recognition
• CPC Class Codes: G06V 30/162 Quantising the image signal
• CPC Class Codes: G06V 30/168 Smoothing or thinning of the pattern; Skeletonisation

Abstract

An image processing method and device computes the image quality as an evaluation value, determine the image quality based on this evaluation value, and employ a restoration process in accordance with image quality when this image quality is poor. The image processing device includes an image quality computation unit to extract a characteristic amount to determine the image quality of the image data entered by an image input device and to compute the characteristic amount as the evaluation value, a binary threshold determination unit to determine a binary threshold value for the image to be processed using an evaluation value obtained by the image quality computation unit, and an image quality improvement unit to determine candidates for image quality improvement unit by extracting sections which have the possibility of image quality deterioration based on the characteristics and to perform image quality improvement on candidates for image quality improvement processing using the evaluation value obtained by said image quality computation unit. The image quality computation unit extracts a characteristic amount of the image in sections with the possibility of image quality deterioration unit determines the image quality using this characteristic amount as an evaluation value; the binary threshold value determination means determines the optimum binary threshold value on the basis of this evaluation value; and the image quality improvement unit extracts candidates for and performs the image quality improvement process only when image quality improvement is necessary.

Claims

1. An image processing method for an image processing device, comprising steps of:

inputting binary coded pixel character image data to said image processing device;

determining a first characteristic amount from said binary coded pixel character image data, wherein the first characteristic amount is based on a count of horizontally convex shapes and a count of black/white pixel transitions;

determining a first evaluation value based on said first characteristic amount;

determining a first plurality of sections of the binary coded pixel character image data as potential deteriorated sections;

modifying the binary coded pixel character image data, based on said first evaluation value, in at least some of said first plurality of sections to produce modified binary coded pixel character image data; and

outputting said modified binary coded pixel character image data.

2. A method according to claim 1, further comprising the step of determining a second plurality of sections of said first plurality of sections,

wherein said step of modifying the binary coded pixel character image data comprises modifying image data in said second plurality of sections by interpolating pixels in said second plurality of sections.

3. A method according to claim 1, further comprising the steps of:

determining each of a plurality of patterns of binary coded pixel characteristics as characteristic points;

determining a second plurality of sections from said first plurality of sections based on characteristic points in said second plurality of sections and image data in said second plurality of sections corresponding to image positions between image positions corresponding to said characteristic points.

4. A method according to claim 1, further comprising the steps of:

determining a threshold value of image deterioration based on said first evaluation value;

determining a section of image data for potential interpolation of pixels;

determining a pixel interval corresponding to said section;

comparing said threshold value to said pixel interval; and

determining whether to perform interpolation of pixels in said portion based on the comparison.

5. A method according to claim 1, further comprising the step of determining portions of image data where said step of modifying the binary coded pixel character image data will not be performed independent of the binary coded pixel character image data corresponding to image positions adjacent the image positions corresponding to any pixel of said portions.

6. An image processing method according to claim 1, wherein said inputting step comprises the step of scanning a document including characters.

7. An image processing method according to claim 1,

further comprising the step of determining a second characteristic value based on said first binary coded pixel character image data, wherein the second characteristic value is a function of a count of continuous black pixel segments longer than a threshold value,

and wherein said first evaluation value is based on both said first and second characteristic values.

8. An image processing method for an image processing device, comprising:

(a) inputting binary coded pixel character image data to said image processing device based on a first binary threshold value;

(b) determining a characteristic amount from the binary coded pixel character image data, wherein the characteristic amount is based on a count of continuous black pixel segments longer than the first binary threshold value;

(c) determining a first evaluation value based on said first characteristic amount;

(d) comparing said first binary threshold value with said first evaluation value;

(e) determining, based on said comparison, whether to replace the binary threshold value on which the input of the binary coded pixel character image data is based with a second binary threshold value;

(f) determining a plurality of second evaluation values;

(g) determining said first evaluation value in step (c) based on said plurality of second evaluation values; and

(h) replacing the binary threshold value on which the input of the binary coded pixel character image data is based with different binary threshold values by repeating steps (a) through (g), until the last determined first evaluation value corresponds to a predetermined optimum imaging value.

9. An image processing method according to claim 8, wherein said inputting step comprises the step of scanning a document including characters.

10. An image processing method for an image processing device, comprising steps of:

(a) inputting binary coded pixel character image data to said image processing device based on a binary threshold value;

determining a first characteristic amount from the binary coded pixel character image data, wherein the first characteristic amount is based on a count of continuous black pixel segments longer than the binary threshold value;

(b) determining an evaluation value based on said first characteristic amount;

(c) comparing said binary threshold value with said evaluation value;

(d) determining, based on said comparison, whether to repeat steps (a) through (d) based on a different binary threshold value;

(e) repeating steps (a) through (d) with a different binary threshold value if a determination is made in step (d) to repeat to steps (a) through (d);

(f) determining a plurality of sections of most recently inputted binary coded pixel character image data as potential deteriorated sections when a determination is made in step (d) not to repeat steps (a) through (d);

(g) modifying the most recently inputted binary coded pixel character image data, based on the last determined evaluation value, in at least some of said plurality of sections to produce modified binary coded pixel image data; and

(h) outputting said modified binary coded pixel character image data from said image processing device.

11. An image processing method according to claim 10, wherein said inputting step comprises the step of scanning a document including characters.

12. A method according to claim 10, wherein the different binary threshold value is based on an average length of continuous black pixel segments longer than the binary threshold value.

13. An image processing device comprising:

an image input device that inputs binary coded pixel character image data to said image processing device;

an image quality computation unit that determines a first characteristic amount based on a count of horizontally convex shapes and a count of black/white pixel transitions from the binary coded pixel character image data, determines a first evaluation value based on said first characteristic amount, and determines quality of the binary coded pixel character image based on said first evaluation value;

an image quality improvement unit that determines a first plurality of sections of the binary coded pixel character image data as potential deteriorated sections, and modifies the binary coded pixel character image data, based on said first evaluation value, in at least some of said first plurality of sections to produce modified binary coded pixel image data; and

an image output device that outputs said modified binary coded pixel image data.

14. An image processing device according to claim 13, wherein said image quality improvement unit determines a second plurality of sections of said first plurality of sections, and modifies the binary coded pixel character image data in said second plurality of sections by interpolating pixels in said second plurality of sections.

15. An image processing device according to claim 13, wherein said image quality improvement unit comprises a processing candidate extraction device that includes:

a characteristic point extraction device that determines each of a plurality of patterns of binary coded pixel characteristics as characteristic points; and

a candidate determination device that determines a second plurality of sections from said first plurality of sections based on characteristic points in said second plurality of sections and image data in said second plurality of sections corresponding to image positions between image positions corresponding to said characteristic points.

16. An image processing device according to claim 13, wherein said image quality improvement unit comprises:

a pixel processing device that includes a threshold value computation device that determines a threshold value of image deterioration based on said first evaluation value;

a processing candidate extraction device that determines a second plurality of sections from said first plurality of sections and a pixel interval for potential interpolation of pixels in each of said second plurality of sections, wherein said pixel processing device determines whether to perform interpolation of pixels in each said pixel interval based a comparison of said threshold value to the length of said pixel interval.

17. An image processing device according to claim 13, wherein said image input device comprises a scanner for scanning documents including characters.

18. An image processing device according to claim 13, wherein said image quality computation unit further determines a second characteristic value based on a count of continuous black pixel segments longer than a threshold value;

and determines said first evaluation value based on both said first and second characteristic values.

19. An image processing device according to claim 13, wherein said image improvement unit comprises a pixel processing device that includes a character cut-out device that excludes a plurality of portions of said binary coded pixel character image data from image modification independent of the binary coded pixel character image data corresponding to image positions adjacent the image positions corresponding to any pixel of said portions.

20. An image processing device comprising:

an image input device that inputs binary coded pixel character image data to said image processing device based on a binary threshold value;

an image quality computation unit that determines a first characteristic amount from the binary coded pixel character image data based on a count of continuous black pixel segments longer than the binary threshold value, and determines a first evaluation value based on said first characteristic amount; and

a binary threshold determination device that compares said binary threshold value with said first evaluation value and determines, based on the comparison, whether to replace the binary threshold value on which the input of the binary coded pixel character image data is based with a different binary threshold value, said binary threshold determination device including;

means for determining a plurality of second evaluation values on which said first evaluation value is based; and

means for changing the binary threshold value on which the input of the binary coded pixel character image data is based to successively different binary threshold values until said first evaluation value reaches a value corresponding to optimum image processing.

21. An image processing device according to claim 20, wherein said image input device comprises a scanner for scanning documents including characters.

22. An image processing device, comprising:

an image input device that inputs binary coded pixel character image data to said image processing device based on a binary threshold value;

an image quality computation unit that determines a characteristic amount from the binary coded pixel character image data, wherein the characteristic amount is based on a count of continuous black pixel segments longer than the binary threshold value, and determines an evaluation value based on said characteristic amount;

a binary threshold determination device that compares a binary threshold value with said evaluation value and determines, based on the comparison, whether to replace the binary threshold value on which the input of the binary coded pixel character image data is based with a different binary threshold value;

an image quality improvement unit that includes (1) a processing candidate extraction device that determines a plurality of sections of the inputted binary coded pixel character image data as potential deteriorated sections, and (2) a pixel processing device that modifies the binary coded pixel character image data, based on said evaluation value, in at least some of said plurality of sections to produce modified binary coded pixel character image data; and

an image output device that outputs said modified binary coded pixel character image data from said image processing device.

23. An image processing device according to claim 22, wherein said image input device comprises a scanner for scanning documents including characters.

24. An image processing device according to claim 22, further comprising means for replacing the binary threshold value with the different binary threshold value, wherein the different binary threshold value is based on an average length of continuous black pixel segments longer than the binary threshold value.

25. An image processing method for an image processing device, comprising:

inputting binary coded pixel character image data to said image processing device based on a first binary threshold value;

determining a characteristic amount from the binary coded pixel character image data, wherein the characteristic amount is based on a count of continuous black pixel segments longer than the first binary threshold value;

determining a first evaluation value based on said first characteristic amount;

comparing said first binary threshold value with said first evaluation value;

determining, based on said comparison, whether to replace the binary threshold value on which the input of the binary coded pixel character image data is based with a second binary threshold value; and

replacing the binary threshold value on which the input of the binary coded pixel character image data is based with the second binary threshold value, wherein the second binary threshold value is based on an average length of continuous black pixel segments longer than the first binary threshold value.

26. An image processing device comprising:

an image input device that inputs binary coded pixel character image data to said image processing device based on a binary threshold value;

an image quality computation unit that determines a first characteristic amount from the binary coded pixel character image data based on a count of continuous black pixel segments longer than the binary threshold value, and determines a first evaluation value based on said first characteristic amount;

a binary threshold determination device that compares said binary threshold value with said first evaluation value and determines, based on the comparison, whether to replace the binary threshold value on which the input of the binary coded pixel character image data is based with a different binary threshold value; and

means for calculating the different binary threshold value as a function of an average length of continuous black pixel segments longer than the binary threshold value.