Image processing method and apparatus and image display apparatus

Abstract

An image processing method extends n-bit input image data by α bits to generate (n+α)-bit source data, where n and α are positive integers, and smoothes the source data. The maximum difference between gray levels of the unsmoothed source data in an area localized around each pixel is calculated, and a mixing ratio is determined from the maximum difference. The smoothed and unsmoothed source data are mixed according to the mixing ratio to generate output image data. In areas with gradually changing gray levels, the output image data are weighted toward the smoothed source data, mitigating image degradation due to quantization and gamma correction. In areas with sharp edges, the output image data are weighted toward the unsmoothed source data, preventing a loss of edge sharpness.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

In the attached drawings:

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

FIGS. 2A to 2G are graphs illustrating the operation of the image display apparatus in the first embodiment;

FIG. 3 illustrates the operation of the data smoother in FIG. 1;

FIGS. 4A to 4C illustrate the operation of the maximum difference calculator in FIG. 1;

FIG. 5 is a block diagram showing the structure of the maximum difference calculator in FIG. 1;

FIGS. 6A and 6B are graphs illustrating the operation of the maximum difference calculator in FIG. 1;

FIGS. 7A to 7G illustrate the operation of the maximum difference calculator in FIG. 1;

FIGS. 8A and 8B are graphs illustrating the operation of the mixing ratio generator in FIG. 1;

FIGS. 9A to 9G are graphs illustrating the operation of the image display apparatus in the first embodiment;

FIG. 10 is a flowchart illustrating the operation of the image display apparatus in the first embodiment;

FIG. 11 is a block diagram showing the structure of an image display apparatus in a second embodiment;

FIG. 12 is a block diagram showing the structure of an image display apparatus in a third embodiment;

FIGS. 13A and 13B are graphs illustrating the operation of the mixing ratio smoother in FIG. 12;

FIG. 14 is a block diagram showing the structure of an image display apparatus in a fourth embodiment of the invention;

FIG. 15 is a block diagram showing the structure of an image display apparatus in a fifth embodiment;

FIGS. 16A to 16D and FIGS. 17A to 17E are graphs illustrating the operation of the fifth embodiment;

FIG. 18 is a flowchart illustrating the operation of the fifth embodiment;

FIG. 19 is a block diagram showing the structure of an image display apparatus in a sixth embodiment;

FIG. 20 is a block diagram showing the structure of an image display apparatus in a seventh embodiment;

FIG. 21 is a block diagram showing the structure of an image display apparatus in an eighth embodiment;

FIG. 22 is a block diagram showing the structure of an image display apparatus in a ninth embodiment;

FIGS. 23A to 23G and FIGS. 24A to 24G are graphs illustrating the operation of the ninth embodiment;

FIG. 25 is a flowchart illustrating the operation of the ninth embodiment; and

FIG. 26 is a block diagram showing the structure of an image display apparatus in a tenth embodiment.

Claims

1. An image processing method comprising: extending n-bit input image data by α bits to generate source data having n+α bits per pixel, where n and α are positive integers;modifying the source data of each pixel according to the source data in an area localized around the pixel to generate smoothed data;calculating a maximum difference between gray levels of the source data in said area;generating a mixing ratio of the smoothed data with respect to the source data, the mixing ratio increasing as said maximum difference decreases; andmixing the smoothed data and the source data according to the mixing ratio to generate and output mixed image data.

2. The image processing method of claim 1, wherein the maximum difference is a maximum difference between pixels separated by not more than a predetermined distance within said area.

3. An image processing apparatus comprising: a bit extender for extending n-bit input image data by α bits to generate source data having n+α bits per pixel, where n and α are positive integers;a first data smoother for modifying the source data of each pixel according to the source data in a first area localized around the pixel to generate first smoothed data;a first maximum difference calculator for calculating a first maximum difference between gray levels of the source data in the first area;a first mixing ratio generator for generating a first mixing ratio, the first mixing ratio increasing as the first maximum difference decreases; anda first data mixer for mixing the first smoothed data and the source data according to the first mixing ratio to generate and output first mixed image data, the mixing proportion of the first smoothed data increasing as the first mixing ratio increases.

4. The image processing apparatus of claim 3, wherein the first maximum difference is a maximum difference between pixels separated by not more than a first predetermined distance within the first area.

5. The image processing apparatus of claim 3, wherein the first mixing ratio generator: sets the first mixing ratio to a first value if the first maximum difference is less than a first threshold;sets the first mixing ratio to a second value if the first maximum difference is greater than a second threshold, the second value being less than the first value, the second threshold being greater than the first threshold; andsets the first mixing ratio to a value that decreases monotonically from the first value to the second value as the first maximum difference varies from the first threshold to the second threshold.

6. The image processing apparatus of claim 3, wherein the first mixing ratio generator: sets the first mixing ratio to a first value if the first maximum difference is less than a threshold; andsets the first mixing ratio to a second value if the first maximum difference is greater than the threshold, the second value being less than the first value.

7. The image processing apparatus of claim 3, further comprising a mixing ratio smoother for smoothing the first mixing ratio and outputting a smoothed first mixing ratio, wherein the data mixer mixes the first smoothed data and the source data according to the smoothed first mixing ratio.

8. The image processing apparatus of claim 3, wherein the first maximum difference calculator calculates the first maximum difference from the n-bit input image data.

9. The image processing apparatus of claim 3, wherein the first area is a linear area extending in a first direction around said pixel, the image processing apparatus further comprising: a second data smoother for modifying the first mixed image data of said each pixel according to the first mixed image data in a second area localized around the pixel to generate second smoothed data, the second area being a linear area extending in a second direction orthogonal to the first direction;a second maximum difference calculator for calculating a second maximum difference between gray levels of the source data in the second area;a second mixing ratio generator for generating a second mixing ratio, the second mixing ratio increasing as the second maximum vertical difference decreases; anda second data mixer for mixing the first mixed image data and the second smoothed data according to the second mixing ratio to generate and output second mixed image data, the mixing proportion of the second smoothed data increasing as the second mixing ratio increases.

10. The image processing apparatus of claim 9, wherein the second maximum difference is a maximum difference between pixels separated by not more than a second predetermined distance within the second area.

11. The image processing method of claim 1, further comprising: transforming the gray scale of the mixed image data to generate transformed data;modifying the transformed value of said each pixel according to the transformed data in said area localized around the pixel to generate smoothed transformed data; andmixing the smoothed transformed data and the transformed data according to the first mixing ratio to generate output image data; whereinas the mixing ratio increases, the mixing proportion of the smoothed transformed data with respect to the transformed data increases.

12. The image processing apparatus of claim 3, further comprising: a gray-scale transformer for transforming a gray scale of the first mixed image data to generate transformed data;a second data smoother for modifying the transformed data of said each pixel according to the transformed data in the first area to generate second smoothed data; anda second data mixer for mixing the transformed data and the second smoothed data according to the first mixing ratio to generate and output second mixed image data, the mixing proportion of the second smoothed data increasing as the first mixing ratio increases.

13. The image processing apparatus of claim 3, further comprising: a gray-scale transformer for transforming a gray scale of the first mixed image data to generate and output transformed data;a second data smoother for modifying the transformed value of said each pixel according to the transformed data in the first area to generate second smoothed data;a second mixing ratio generator for generating a second mixing ratio, the second mixing ratio increasing as the first maximum difference decreases; anda second data mixer for mixing the transformed data and the second smoothed data according to the first mixing ratio to generate and output mixed output image data, the mixing proportion of the second smoothed data increasing as the first mixing ratio increases.

14. The image processing apparatus of claim 3, further comprising a gray-scale transformer for transforming a gray scale of the source data and outputting the transformed source data to the first data smoother and the first data mixer, wherein the first data smoother and the first data mixer operate on the transformed source data.

15. The image processing apparatus of claim 3, wherein the first area is a linear area extending in a first direction around said pixel, the image processing apparatus further comprising: a second data smoother for modifying the first mixed image data of said each pixel according to the first mixed image data in a second area localized around the pixel to generate second smoothed data, the second area being a linear area extending in a second direction orthogonal to the first direction;a second maximum difference calculator for calculating a second maximum difference between gray levels of the source data in the second area;a second mixing ratio generator for generating a second mixing ratio, the second mixing ratio increasing as the second maximum difference decreases;a second data mixer for mixing the first mixed image data and the second smoothed data according to the second mixing ratio to generate second mixed image data, the mixing proportion of the second smoothed data increasing as the second mixing ratio increases;a gray-scale transformer for transforming a gray scale of the second mixed image data and outputting the transformed data;a third data smoother for modifying the transformed data of said each pixel according to the transformed data in the first area to generate third smoothed data; anda third data mixer for mixing the third smoothed data and the transformed data output according to the first mixing ratio to generate third mixed image data, the mixing proportion of the third smoothed data increasing as the first mixing ratio increases;a fourth data smoother for modifying the third mixed image data of said each pixel according to the third mixed image data in the second area to generate fourth smoothed data; anda fourth data mixer for mixing the third mixed image data and the fourth smoothed data according to the second mixing ratio to generate and output fourth mixed image data, the mixing proportion of the fourth smoothed data increasing as the second mixing ratio increases.

16. An image processing apparatus comprising: a gray-scale transformer for receiving input image data and transforming a gray scale thereof to generate transformed data;a data smoother for modifying the transformed data of said each pixel according to the transformed data in an area localized around the pixel to generate smoothed data;a maximum difference calculator for calculating, for said each pixel, a maximum difference between gray levels of the input image data in said area;a mixing ratio generator for generating a mixing ratio, the mixing ratio increasing as said maximum difference decreases; anda data mixer for mixing the transformed data and the smoothed data according to said mixing ratio to generate and output mixed image data, the mixing proportion of the smoothed data increasing as the mixing ratio increases.

17. The image processing apparatus of claim 16, wherein the maximum difference is a maximum difference between pixels separated by not more than a predetermined distance within said area.

18. An image display apparatus comprising: the image processing apparatus of claim 3;a receiver for receiving an analog image signal and converting the analog image signal to n-bit digital image data for input to the image processing apparatus; anda display unit for displaying an image according to the first mixed image data.

19. An image display apparatus comprising: the image processing apparatus of claim 3;a receiver for receiving an analog image signal and converting the analog image signal to n-bit digital image data for input to the image processing apparatus;a gray-scale pseudo-enhancement processor for converting the first mixed image data from (n+α) bits per pixel to n bits per pixel, representing lost gray levels by distributions of output gray levels, to generate n-bit output image data; anda display unit for displaying the n-bit output image data.