Image processing method and image processing device

• US 5,940,524 A
• Filed: 02/19/1998
• Issued: 08/17/1999
• 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: Aoki, Mikio, Kuwata, Naoki, Murayama, Yasuhiko
• Primary Examiner(s): Mancuso, Joseph
• Assistant Examiner(s): Bali, Vikkram
• Application Number:
  US09/025,800
• Time in Patent Office: 544 Days
• Field of Search: 382/248, 382/250, 382/260, 382/261, 382/270, 382/271, 382/272, 382/112, 382/176, 382/273, 375/240, 358/401, 358/405, 358/406, 358/462, 358/465, 358/466
• US Class Current: 382/112
• 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:

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

dividing the binary coded pixel character image data into a plurality of data blocks representative of blocks of pixels of an image;

performing a first orthogonal transformation with respect to the data blocks;

determining an evaluation value based on the first orthogonal transformation performed with respect to the data blocks;

modifying pixel values of the binary coded pixel character image data based on the evaluation value to produce modified binary coded pixel character image data; and

outputting the modified binary coded pixel character image data.

2. A method according to claim 1, further including performing a second orthogonal transformation with respect to said data blocks, wherein said evaluation value is a function of one of:

a sum of the first and second orthogonal transformations; and

a difference between the first and second orthogonal transformations.

3. A method according to claim 1, wherein modifying the pixel values of the binary coded pixel character image data comprises correcting the pixel values of the binary coded pixel character image data based on the evaluation value to produce corrected binary coded pixel character image data that more closely corresponds to an ideal version of the image.

4. A method according to claim 1, wherein the modified binary coded pixel character image data is corrected binary coded pixel character image data that more closely corresponds to an ideal version of the image.

5. A method according to claim 1, wherein modifying the pixel values of the binary coded pixel character image data comprises improving the pixel values of the binary coded pixel character image data based on the evaluation value to produce improved binary coded pixel character image data that more closely corresponds to an ideal version of the image.

6. A method according to claim 1, wherein the modified binary coded pixel character image data is improved binary coded pixel character image data that more closely corresponds to an ideal version of the image.

7. An image processing device comprising:

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

an image quality computation unit that divides a plurality of pixels of the binary coded pixel character image data into blocks of pixels, determines an evaluation value based on an orthogonal transformation performed with respect to the blocks of pixels, and determines input image quality based on the 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 pixel values of the binary coded pixel character image data in at least some of said first plurality of sections to produce modified binary coded pixel character image data based on said evaluation value; and

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

8. An image processing device according to claim 7, wherein said evaluation value is a function of one of a sum and a difference of orthogonal transformations performed with respect to the blocks of pixels.

9. An image processing device according to claim 7, wherein the image quality improvement unit corrects the pixel values of the binary coded pixel character image data in at least some of said first plurality of sections based on said evaluation value to produce corrected binary coded pixel character image data that more closely corresponds to an ideal version of the image.

10. An image processing device according to claim 7, wherein the modified binary coded pixel character image data is corrected binary coded pixel character image data that more closely corresponds to an ideal version of the image.

11. An image processing device according to claim 7, wherein the image quality improvement unit improves the pixel values of the binary coded pixel character image data in at least some of said first plurality of sections based on said evaluation value to produce improved binary coded pixel character image data that more closely corresponds to an ideal version of the image.

12. An image processing device according to claim 7, wherein the modified binary coded pixel character image data is improved binary coded pixel character image data that more closely corresponds to an ideal version of the image.

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

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

dividing the binary coded pixel character image data into a plurality of data blocks representative of blocks of pixels of an image;

performing a first orthogonal transformation with respect to the data blocks;

determining an evaluation value based on the first orthogonal transformation performed with respect to the data blocks;

correcting the binary coded pixel character image data based on the evaluation value to produce corrected binary coded pixel character image data that more closely corresponds to an ideal version of the image; and

outputting the corrected binary coded pixel character image data.

14. An image processing device comprising:

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

an image quality computation unit that divides a plurality of pixels of the binary coded pixel character image data into blocks of pixels, determines an evaluation value based on an orthogonal transformation performed with respect to the blocks of pixels, and determines input image quality based on the 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 corrects the binary coded pixel character image data in at least some of said first plurality of sections to produce, based on said evaluation value, corrected binary coded pixel character image data that more closely corresponds to an ideal version of the image; and

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

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

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

dividing the binary coded pixel character image data into a plurality of data blocks representative of blocks of pixels of an image;

performing a first orthogonal transformation with respect to the data blocks;

determining an evaluation value based on the first orthogonal transformation performed with respect to the data blocks;

improving the binary coded pixel character image data based on the evaluation value to produce improved binary coded pixel character image data that more closely corresponds to an ideal version of the image; and

outputting the corrected binary coded pixel character image data.

16. An image processing device comprising:

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

an image quality computation unit that divides a plurality of pixels of the binary coded pixel character image data into blocks of pixels, determines an evaluation value based on an orthogonal transformation performed with respect to the blocks of pixels, and determines input image quality based on the 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 improves the binary coded pixel character image data in at least some of said first plurality of sections to produce, based on said evaluation value, improved binary coded pixel character image data that more closely corresponds to an ideal version of the image; and

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