Image display apparatus and method employing selective smoothing

Abstract

An image display device detects mutually adjacent bright and dark parts of an image and detects fine bright lines in the image. Bright parts of the image that are not fine bright lines are smoothed if they are adjacent to dark parts. This smoothing scheme improves the visibility of dark features on bright backgrounds without impairing the visibility of fine bright lines on dark backgrounds.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

In the attached drawings:

FIG. 1 is a block diagram showing an image display device in a first embodiment of the invention;

FIG. 2 is a block diagram showing an exemplary structure of the feature detection unit in FIG. 1;

FIG. 3 is a block diagram showing an exemplary structure of the white line detection unit in FIG. 1;

FIGS. 4A and 4B respectively illustrate the operation of the second-order differentiator and the comparator in FIG. 3;

FIG. 5 is a block diagram showing an exemplary structure of the control signal modification unit in FIG. 1;

FIG. 6 is a block diagram showing an exemplary structure of one of the smoothing units in FIG. 1;

FIG. 7 is a block diagram showing an exemplary structure of a generic filter usable in the smoothing unit in FIG. 6;

FIG. 8 illustrates the filtering characteristic of the generic filter in FIG. 7;

FIGS. 9A, 9B, and 9C show exemplary gray levels that would be displayed without smoothing;

FIGS. 10A and 10B show the filtering characteristic in FIG. 8 applied to red, green, and blue cells;

FIGS. 11A, 11B, and 11C show exemplary image data obtained by selectively smoothing the image data in FIGS. 9A, 9B, and 9C;

FIG. 12 is a flowchart illustrating the operation of the image display device in the first embodiment;

FIG. 13 is a block diagram showing an image display device in a second embodiment;

FIG. 14 is a block diagram showing an exemplary structure of the white line detection unit in FIG. 13;

FIG. 15 is a block diagram showing an image display device in a third embodiment;

FIG. 16 is a block diagram showing an image display device in a fourth embodiment;

FIG. 17 is a block diagram showing an image display device in a fifth embodiment;

FIG. 18 is a block diagram showing an exemplary structure of the feature detection unit in FIG. 17;

FIG. 19 is a block diagram showing an image display device in a sixth embodiment;

FIG. 20 is a block diagram showing an image display device in a seventh embodiment;

FIG. 21 is a block diagram showing an image display device in an eighth embodiment;

FIG. 22 is a block diagram showing an exemplary structure of the feature detection unit in FIG. 21;

FIGS. 23A, 23B, and 23C show exemplary gray levels that would be displayed without smoothing;

FIGS. 24A, 24B, and 24C illustrate pixel brightnesses obtained from image data in FIGS. 23A, 23B, and 23C;

FIGS. 25A, 25B, and 25C show exemplary image data obtained by selectively smoothing the image data in FIGS. 23A, 23B, and 23C; and

FIG. 26 is a flowchart illustrating the operation of the image display device in the eighth embodiment.

Claims

1. An image display device for displaying an image according to image data, comprising: a feature detection unit for detecting, from the image data, bright parts of the image that are adjacent to dark parts of the image, the bright parts having a higher brightness than the dark parts, and thereby generating a first selection control signal;a white line detection unit for detecting parts of the image that are adjacently between darker parts of the image, and thereby generating a white line detection signal;a control signal modification unit for modifying the first selection control signal according to the white line detection signal and thereby generating a second selection control signal;a smoothing unit for selectively performing a smoothing process on the input image data according to the second selection control signal, thereby generating selectively smoothed image data; anda display unit for displaying the image according to the selectively smoothed image data.

2. The image display device of claim 1, wherein the control signal modification unit generates the second selection control signal so that when the first selection control signal indicates a bright part adjacent to a dark part and the white line detection signal does not indicate detection of a white line, the smoothing unit processes the image data with a first filtering characteristic, and when the first selection control signal indicates a bright part adjacent to a dark part and the white line detection signal indicates detection of a white line, the smoothing unit processes the image data with a second filtering characteristic having less smoothing effect than the first filtering characteristic.

3. The image display device of claim 2, wherein the second filtering characteristic has no smoothing effect.

4. The image display device of claim 1, wherein the white line detection unit generates the white line detection signal according to luminance data in the image data.

5. The image display device of claim 4, wherein the white line detection unit takes a second derivative of the luminance data.

6. The image display device of claim 1, wherein: the feature detection unit generates a separate first selection control signal for each of three colors in the image data;the control signal modification unit modifies the first selection control signal of each of the three colors according to the white line detection signal and thereby generates a separate second selection control signal for each of the three colors; andthe smoothing unit performs the smoothing process on the image data of each of the three colors according to the corresponding second selection control signal.

7. The image display device of claim 1, wherein the feature detection unit generates the first selection control signal according to luminance data in the image data.

8. The image display device of claim 1, wherein the feature detection unit detects parts of the input image brighter than a threshold value that are adjacent to parts of the input image darker than the threshold value as said bright parts of the image that are adjacent to dark parts of the image.

9. The image display device of claim 1, wherein the feature detection unit detects parts of the image that are brighter than adjacent parts of the image as said bright parts of the image that are adjacent to dark parts of the image.

10. The image display device of claim 9, wherein the feature detection unit detects only parts of the image that are darker than a predetermined threshold value as said bright parts of the image that are adjacent to dark parts of the image.

11. A method of displaying an image according to image data, comprising: detecting, from the image data, bright parts of the image that are adjacent to dark parts of the image, the bright parts having a higher brightness than the dark parts, and thereby generating a first selection control signal;detecting parts of the image that are adjacently between darker parts of the image and thereby generating a white line detection signal;modifying the first selection control signal according to the white line detection signal and thereby generating a second selection control signal;selectively performing a smoothing process on the image data according to the second selection control signal, thereby generating selectively smoothed image data; anddisplaying the image according to the selectively smoothed image data.

12. The method of claim 11, wherein when the first selection control signal indicates a bright part adjacent to a dark part and the white line detection signal does not indicate detection of a white line, the second selection control signal causes the image data to be processed with a first filtering characteristic, and when the first selection control signal indicates a bright part adjacent to a dark part and the white line detection signal indicates detection of a white line, the second selection control signal causes the image data to be processed with a second filtering characteristic having less smoothing effect than the first filtering characteristic.

13. The method of claim 12, wherein the second filtering characteristic has no smoothing effect.

14. The method of claim 11, wherein the white line detection signal is generated according to luminance data in the image data.

15. The method of claim 14, wherein the white line detection signal is generated by taking a second derivative of the luminance data.

16. The method of claim 11, wherein: generating a first selection control includes generating a separate first selection control signal for each of three colors in the image data;modifying the first selection control signal includes modifying the first selection control signal of each of the three colors according to the white line detection signal, thereby generating a separate second selection control signal for each of the three colors; andselectively performing a smoothing process includes performing a smoothing process on the image data of each of the three colors according to the corresponding second selection control signal.

17. The method of claim 11, wherein the first selection control signal is generated according to luminance data in the image data.

18. The method of claim 11, wherein detecting bright parts of the image that are adjacent to dark parts of the image includes detecting parts of the image brighter than a threshold value that are adjacent to parts of the image darker than the threshold value.

19. The method of claim 11, wherein detecting bright parts of the image that are adjacent to dark parts of the image includes detecting parts of the image that are brighter than adjacent parts of the image.

20. The method of claim 19, wherein said parts of the image that are brighter than adjacent parts of the image are detected as said bright parts of the image that are adjacent to dark parts of the image only if they are darker than a predetermined threshold value.