Method and apparatus for enhancement of digital image quality

• US 20040017579A1
• Filed: 02/21/2003
• Published: 01/29/2004
• Est. Priority Date: 07/27/2002
• Status: Abandoned Application

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Lim, Sung-hyun
• Application Number:
  US10/370,110
• Publication Number:
  US 20040017579A1
• Time in Patent Office: Days
• US Class Current: 358/1.9
• CPC Class Codes: H04N 1/40062 Discrimination between different image types, e.g. two-tone, continuous tone
• CPC Class Codes: H04N 1/56 Processing of colour picture signals H04N1/52 takes precedence

Abstract

A digital image quality enhancement method and apparatus convert RGB color data of a pixel of interest into color data having a brightness component and a saturation component, and segment the pixel of interest into a background pixel, an image pixel, or a text pixel using the brightness component and the saturation component. The method and apparatus label the pixel of interest as a text area, a background area, or an image area using history information regarding the pixel of interest, where the history information is a number of successive background pixels or image pixels before the pixel of interest. An image quality of the pixel of interest is enhanced to degrees corresponding to the area labeled and the method determines whether the pixel of interest is a final pixel of which an image quality is to be improved.

Claims

1. A digital image quality enhancement method where image data comprising pixels with a predetermined resolution is obtained by scanning a script comprising a combination of a background, a text, and an image, the method comprising:

converting RGB color data of a pixel of interest into color data having a brightness component and a saturation component;

classifying the pixel of interest into any of a background pixel, an image pixel, and a text pixel using the brightness component and the saturation component;

storing a number of successive background pixels or image pixels before the pixel of interest and the pixel of interest, as history information regarding the pixel of interest;

labeling the pixel of interest as any of a text area, a background area, and an image area using the history information regarding the pixel of interest;

enhancing an image quality of the pixel of interest to different degrees depending on the area labeled; and

determining whether the pixel of interest is a final pixel of which the image quality is to be improved.

2. The digital image quality enhancement method of claim 1, wherein, in the conversion of the RGB color data, the RGB color data is converted into YCbCr color data, where a Y component is adopted as the brightness component, and the saturation component is obtained from Cb and Cr components.

3. The digital image quality enhancement method of claim 2, wherein the saturation component is a sum of absolute values of the Cb and Cr components.

4. The digital image quality enhancement method of claim 2, wherein the saturation component is a root mean square (RMS) of the Cb and Cr components.

5. The digital image quality enhancement method of claim 1, wherein the pixel of interest is classified into any of the background pixel, the image pixel, and the text pixel by using one of a predetermined brightness threshold for the brightness component and a predetermined saturation threshold for the saturation component.

6. The digital image quality enhancement method of claim 5, wherein the pixel of interest is classified into any of the background pixel, the image pixel, and the text pixel by using one of a high brightness threshold and a low brightness threshold as the predetermined brightness threshold.

7. The digital image quality enhancement method of claim 6, wherein when the brightness component of the pixel of interest is greater than the high brightness threshold and the saturation component is smaller than the saturation threshold, the pixel of interest is classified into the background pixel.

8. The digital image quality enhancement method of claim 7, wherein when the brightness component of the pixel of interest is greater than the high brightness threshold or the saturation component is greater than the saturation threshold, the pixel of interest is classified into the image pixel.

9. The digital image quality enhancement method of claim 8, wherein when the pixel of interest is classified into neither the background pixel nor the image pixel, the pixel of interest is classified into the text pixel.

10. The digital image quality enhancement method of claim 1, further comprising:

performing smoothing to reduce a high frequency component of the brightness component.

11. The digital image quality enhancement method of claim 1, wherein when the pixel of interest is classified as the background pixel, the pixel of interest and the number of successive background pixels that continue in the upper direction of the pixel of interest are stored as a background history information of the pixel of interest.

12. The digital image quality enhancement method of claim 11, wherein when the pixel of interest is classified as the background pixel and the pixel of interest and the number of successive background pixels that continue in the upper direction of the pixel of interest are a predetermined number of m or greater, the number m is stored as the background history information of the pixel of interest.

13. The digital image quality enhancement method of claim 1, wherein when the pixel of interest is classified as the image pixel, the pixel of interest and the number of successive image pixels that continue in an upper direction of the pixel of interest are stored as an image history information of the pixel of interest.

14. The digital image quality enhancement method of claim 13, wherein when the pixel of interest is classified as the image pixel and the pixel of interest and the number of image pixels that continue in the upper direction of the pixel of interest are a predetermined number of p or greater, the number p is stored as the image history information of the pixel of interest.

15. The digital image quality enhancement method of claim 1, wherein when the pixel of interest is classified as a non-background pixel, the pixel of interest and a number of non-background pixels that continue in a left direction of the pixel of interest are stored as an image history information of the pixel of interest.

16. The digital image quality enhancement method of claim 15, wherein when the pixel of interest is classified as the non-background pixel and the number of non-background pixels and the pixel of interest that continue in the left direction of the pixel of interest are a predetermined number of r or greater, the number r is stored as the image history information of the pixel of interest.

17. The digital image quality enhancement method of claim 1, wherein the labeling of the pixel of interest comprises:

classifying the pixel of interest into any of a background feature pixel connected to the successive background pixels and an image feature pixel connected to the successive image pixels by using the history information stored regarding the pixel of interest;

background-labeling the pixel of interest classified into the background feature pixel where the pixel of interest belongs to the background area; and

image-labeling the pixel of interest classified into the image feature pixel where the pixel of interest belongs to the image area.

18. The digital image quality enhancement method of claim 17, wherein, when the pixel of interest on the line of interest is classified into the image feature pixel the labeling of the pixel of interest further comprises:

propagating image labeling leftward of the pixel of interest where consecutive pixels before the pixel of interest, based on the pixel of interest being classified into the image feature pixel, belong to the image area.

19. The digital image quality enhancement method of claim 17, wherein, when the pixel of interest is classified into neither the background feature pixel nor the image feature pixel and a pixel directly above the pixel of interest on a line of interest is image-labeled, the labeling of the pixel of interest further comprises:

propagating image labeling downward the pixel above the pixel of interest where the pixel of interest belongs to the image area.

20. The digital image quality enhancement method of claim 19, wherein when the pixel of interest is classified into neither the background feature pixel nor the image feature pixel, and the pixel directly above the pixel of interest is not image-labeled, the labeling of the pixel interest further comprises:

text-labeling the pixel of interest where the pixel of interest belongs to the text area.

21. The digital image quality enhancement method of claim 17, wherein, when the pixel of interest is classified into the image feature pixel, the labeling of the pixel of interest further comprises:

propagating image labeling rightward of the pixel of interest where all of the pixels that exist after the pixel of interest and before the background feature pixel belong to the image area.

22. The digital image quality enhancement method of claim 17, wherein, when a pixel before the pixel of interest on the line of interest is background-labeled, the labeling of the pixel of interest further comprises:

background-labeling the pixel of interest when the pixel of interest belongs to the background area, and the pixel of interest is the background pixel, and text-labeling the pixel of interest when the pixel of interest belongs to the text area, and the pixel of interest is not the background pixel.

23. The digital image quality enhancement method of claim 17, wherein when a predetermined number, n, of pixels, which comprise each of the pixels in which a size of the background history information is a predetermined number m or greater, continue in a left direction of the pixel of interest, the pixel of interest is classified into the background feature pixel.

24. The digital image quality enhancement method of claim 17, wherein when a predetermined number, q, of pixels, which comprise each of the pixels in which a size of the image history information is a predetermined number p or greater, continue in a left direction of the pixel of interest, the pixel of interest is classified into the image feature pixel.

25. The digital image quality enhancement method of claim 17, wherein when the pixel of interest has the image history information with a size being a predetermined number r or greater and r or more pixels not classified into background pixels exist on a left side of the pixel of interest, the pixel of interest is classified into the image feature pixel.

26. The digital image quality enhancement method of claim 1, wherein, in the enhancement of the image quality, different image quality enhancements are applied according to a brightness of the pixel of interest designated as the text area.

27. The digital image quality enhancement method of claim 26, wherein the enhancement of the image quality comprises classifying the brightness of the pixel of interest into three brightness groups based on brightness thresholds, processing a brightest pixel to be complete white, processing a darkest pixel to be complete black, and sharpening a middle bright pixel.

28. The digital image quality enhancement method of claim 27, wherein unsharpened masking is performed by determining an emphasis coefficient to be at least a predetermined value to increase an edge emphasis effect.

29. The digital image quality enhancement method of claim 1, wherein the enhancement of the image quality comprises unsharpened masking with respect to the pixel of interest designated as the image area.

30. The digital image quality enhancement method of claim 29, wherein the unsharpened masking is performed by determining an emphasis coefficient to be a predetermined value or less.

31. A digital image quality enhancement method, the method comprising:

converting RGB color data of a pixel of interest into color data having a brightness component and a saturation component;

segmenting the pixel of interest into a background pixel, an image pixel, or a text pixel using the brightness component and the saturation component;

labeling the pixel of interest as a text area, a background area, or an image area using history information regarding the pixel of interest, wherein the history information is a number of successive background pixels or image pixels before the pixel of interest;

enhancing an image quality of the pixel of interest to degrees corresponding to the area labeled; and

determining whether the pixel of interest is a final pixel of which an image quality is to be improved.

32. The digital image quality enhancement method of claim 31, further comprising:

smoothing the color data to reduce a high frequency component in the brightness component.

33. The digital image quality enhancement method of claim 31, wherein the pixel of interest is segmented as the background pixel, the image pixel, or the text pixel using a predetermined high brightness threshold and a predetermined low brightness threshold.

34. The digital image quality enhancement method of claim 31, wherein when the brightness component of the pixel of interest is greater than the high brightness threshold and the saturation component is smaller than a saturation threshold, the pixel of interest is segmented as the background pixel.

35. The digital image quality enhancement method of claim 31, wherein when the brightness component of the pixel of interest is greater than the low brightness threshold or the saturation component of the pixel of interest is greater than the saturation threshold while the pixel of interest is not segmented as the background pixel, the pixel of interest is segmented as the image pixel.

36. The digital image quality enhancement method of claim 31, wherein when the brightness component of the pixel of interest is smaller than the low brightness threshold or greater than the high brightness threshold or the saturation component of the pixel of interest is greater than the saturation threshold, the pixel of interest is segmented as the image pixel.

37. The digital image quality enhancement method of claim 31, wherein when the pixel of interest is segmented as neither the background pixel nor the image pixel, the pixel of interest is segmented as the text pixel.

38. The digital image quality enhancement method of claim 31, wherein, in the conversion of the RGB color data, the RGB color data is converted into YCbCr color data, where a Y component is adopted as the brightness component, and the saturation component is obtained from Cb and Cr components.

39. The digital image quality enhancement method of claim 31, wherein when the pixel of interest is classified as the background pixel, the pixel of interest and the number of successive background pixels that continue in the upper direction of the pixel of interest are stored as a background history information of the pixel of interest.

40. The digital image quality enhancement method of claim 39, wherein when the pixel of interest is classified as the background pixel and the number of successive background pixels that continue in the upper direction of the pixel of interest are a predetermined number of m or greater, the number m is stored as the background history information of the pixel of interest.

41. The digital image quality enhancement method of claim 31, wherein when the pixel of interest is classified as the image pixel, the pixel of interest and the number of successive image pixels and that continue in an upper direction of the pixel of interest are stored as an image history information of the pixel of interest.

42. The digital image quality enhancement method of claim 41, wherein when the pixel of interest is classified as the image pixel and the number of image pixels that continue in the upper direction of the pixel of interest are a predetermined number of p or greater, the number p is stored as the image history information of the pixel of interest.

43. The digital image quality enhancement method of claim 31, wherein when the pixel of interest is classified as a non-background pixel, the pixel of interest and a number of non-background pixels and the pixel of interest that continue in a left direction of the pixel of interest are stored as an image history information of the pixel of interest.

44. The digital image quality enhancement method of claim 43, wherein when the pixel of interest is classified as the non-background pixel and the pixel of interest and the number of non-background pixels that continue in the left direction of the pixel of interest are a predetermined number of r or greater, the number r is stored as the image history information of the pixel of interest.

45. The digital image quality enhancement method of claim 31, wherein the labeling of the pixel of interest comprises:

classifying the pixel of interest into any of a background feature pixel connected to the successive background pixels and an image feature pixel connected to the successive image pixels by using the history information stored regarding the pixel of interest;

background-labeling the pixel of interest classified into the background feature pixel where the pixel of interest belongs to the background area; and

image-labeling the pixel of interest classified into the image feature pixel where the pixel of interest belongs to the image area.

46. A digital image quality enhancement apparatus, comprising:

a classification unit classifying a pixel of interest in image data comprising pixels with a predetermined resolution and obtained by scanning a script comprising a combination of a background, a text, and an image into any of a text area, a background area, and an image area; and

an image quality enhancement unit enhancing a quality of an image to different degrees according to an area to which the pixel of interest belongs, wherein the classification unit comprises;

a color data conversion unit converting RGB color data of the pixel of interest into brightness/saturation data having a brightness component and a saturation component;

a pixel segmentation unit classifying the pixel of interest into any of a background pixel, an image pixel, and a text pixel by using the brightness/saturation data and outputting a result of the classification as a pixel segmentation signal;

a history information storage unit counting a number of successive background pixels before the pixel of interest using the pixel segmentation signal and storing the counted number of background pixels as background history information in a predetermined address corresponding to the pixel of interest, or counting a number of successive image pixels before the pixel of interest and storing the counted number of image pixels as image history information in the address corresponding to the pixel of interest; and

an area segmentation unit receiving the background or image history information regarding the pixel of interest from the history information storage unit, classifying the pixel of interest into any of the text area, the background area, and the image area by using the received background or image history information, labeling the pixel of interest as the text when the pixel of interest is classified into the text area, labeling the pixel of interest as the background when the pixel of interest is classified into the background area, and labeling the pixel of interest as the image when the pixel of interest is classified into the image area.

47. The digital image quality enhancement apparatus of claim 46, wherein the image quality enhancement unit improves the quality of the image by receiving a text labeling signal for the pixel of interest, a background labeling signal for the pixel of interest, or an image labeling signal for the pixel of interest from the area segmentation unit and classifies the brightness/saturation data of the text-labeled pixel of interest into at least two classes based on a predetermined brightness threshold.

48. The digital image quality enhancement apparatus of claim 46, wherein the image quality enhancement unit receives a text labeling signal of the pixel of interest, a background labeling signal of the pixel of interest, or an image labeling signal of the pixel of interest from the area segmentation unit and improves the image quality of an image-labeled pixel of interest using an unsharpened mask.

49. The digital image quality enhancement apparatus of claim 46, further comprising:

a smoothing unit performing smoothing to reduce a high frequency component of the brightness component of the brightness/saturation data using a low pass filter and outputting new brightness/saturation data having a smoothed brightness component,

wherein the pixel segmentation unit classifies the pixel of interest into one of the background pixel, the image pixel, and the text pixel using the new brightness/saturation data and outputting a result of the classification as a pixel segmentation signal.

50. A digital image quality enhancement apparatus, comprising:

a color data conversion unit converting RGB color data of a pixel of interest into color data having a brightness component and a saturation component;

a pixel segmentation unit segmenting the pixel of interest into a background pixel, an image pixel, or a text pixel using the brightness component and the saturation component;

a history information storage unit labeling the pixel of interest as a text area, a background area, or an image area using history information regarding the pixel of interest, wherein the history information is a number of successive background pixels or image pixels before the pixel of interest;

an image quality enhancement unit enhancing an image quality of the pixel of interest to degrees corresponding to the area labeled; and

an area segmentation unit determining whether the pixel of interest is a final pixel of which an image quality is to be improved.