Apparatus and method for adjusting brightness

• US 20060221100A1
• Filed: 08/08/2005
• Published: 10/05/2006
• Est. Priority Date: 03/30/2005
• Status: Active Grant

• Current Assignee: Quanta Computer
• Original Assignee: Quanta Computer
• Inventors: Tsai, Tsan-Hung, Kao, Hsu-Chia, Huang, Yu-Wen
• Granted Patent: US 7,688,338 B2
• Time in Patent Office: Days
• US Class Current: 345/690
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 2320/066 for control of contrast
• CPC Class Codes: G09G 2340/0428 Gradation resolution change
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/2007 Display of intermediate tones

Abstract

The invention discloses an apparatus for adjusting the brightness of the i^th image of an inputted image sequence in a display system. The image sequence includes a plurality of images which each consists of a plurality of pixels. The apparatus includes a first calculating module for calculating a current brightness ratio, a second calculating module for calculating an averaged brightness ratio, a judging module for outputting one selected from the current brightness ratio or the averaged brightness ratio as an outputted brightness ratio, a determining module for storing a plurality of brightness ratios and the corresponding gains and for determining the gain corresponding to the outputted brightness ratio, and an adjusting module for multiplying the gray scale level of each pixel of the i^th image by the gain corresponding to the outputted brightness ratio respectively, so as to adjust the brightness of the i^th image.

Claims

1. In a display system, an inputted video sequence comprising N image frames to be displayed which each consists of T pixels, each pixel of each image frame comprising M color components and M gray scale levels which each corresponds to one of the M color components, N, T, and M being a natural number, respectively, an apparatus functioning adjusting the M gray scale levels of the M color components of the ith image frame in the video sequence, i being an integer index ranging from 1 to N, the gray scale levels of the image frames previous to the ith image frame having been adjusted, each of the image frames previous to the ith image frame having a respective brightness ratio which relates to the gray scale levels been determined of said one image frame and is within an allowable range, a plurality of gains which each corresponds to one of the brightness ratios varying within the allowable range being previously provided, said apparatus comprising:

a first calculating module for retrieving all of the gray scale levels of all pixels of the ith image frame, and calculating, according to all of the gray scale levels of all pixels of the ith image frame, a current brightness ratio;

a second calculating module for calculating, according to all of the brightness ratios of the image frames previous to the ith image frame and the current brightness ratio, an averaged brightness ratio;

a judging module for receiving the current brightness ratio and the averaged brightness ratio, and outputting one selected from the current brightness ratio or the averaged brightness ratio as an outputted brightness ratio, wherein the outputted brightness ratio is also within the allowable range;

a determining module for storing the brightness ratios varying within the allowable range and the corresponding gains, the determining module having an input coupled to receive the outputted brightness ratio, the determining module also functioning determining the gain corresponding to the outputted brightness ratio; and

an adjusting module for receiving the gain corresponding to the outputted brightness ratio, and multiplying the gray scale level of each color component of the ith image frame by the gain corresponding to the outputted brightness ratio, respectively.

2. The apparatus of claim 1, wherein the M color components are R, G, and B (Red, Green, and Blue) color components respectively conforming to RGB color space.

3. The apparatus of claim 2, wherein the current brightness ratio BR_i is calculated by the first calculating module via the following equation:

${\mathrm{BR}}_i=\frac{Y_i}{Y_{\mathrm{total}}};<br><br>$

wherein Y₁ represents the sum of all of the gray scale levels of all pixels of the ith image frame, and Y_total represents a pre-defined sum of all of the gray scale levels of all pixels of each image frame.

4. The apparatus of claim 3, wherein the sum of all of the gray scale levels of all pixels of the ith image frame Y_i is calculated via the following equation:

$Y_i=0.3<br><br>\underset{j=1}{\overset{L}{\sum <br><br>}}<br><br>{\mathrm{GR}}_j+0.59<br><br>\underset{j=1}{\overset{L}{\sum <br><br>}}<br><br>{\mathrm{GG}}_j+0.11<br><br>\underset{j=1}{\overset{L}{\sum <br><br>}}<br><br>{\mathrm{GB}}_j$

wherein GR_j represents the gray scale level of the R color component of the jth pixel of the ith image frame, GG_j represents the gray scale level of the G color component of the jth pixel of the ith image frame, and GB_j represents the gray scale level of the B color component of the jth pixel of the ith image frame, and j is an integer index ranging from 1 to T.

5. The apparatus of claim 4, wherein the averaged brightness ratio BR_avg is calculated by the second calculating module via the following equation:

${\mathrm{BR}}_{\mathrm{avg}}=\frac{1}{i}<br><br>\underset{k=1}{\overset{i}{\sum <br><br>}}<br><br>{\mathrm{BR}}_k;<br><br>$

6. The apparatus of claim 5, wherein the judging module further stores a threshold, when the difference between the current brightness ratio and the averaged brightness ratio is larger than the threshold, the judging module outputs the current brightness ratio as the outputted brightness ratio and replaces all of the brightness ratios of the image frames previous to the ith image frame by the current brightness ratio of the ith image frame, and when the difference between the current brightness ratio and the averaged brightness ratio is smaller than the threshold, the judging module outputs the averaged brightness ratio as the outputted brightness ratio.

7. In a display system, an inputted video sequence comprising N image frames to be displayed which each consists of T pixels, each pixel of each image frame comprising M color components and M gray scale levels which each corresponds to one of the M color components, N, T, and M being a natural number, respectively, a method functioning adjusting the M gray scale levels of the M color components of the ith image frame in the video sequence, i being an integer index ranging from 1 to N, the gray scale levels of the image frames previous to the ith image frame having been adjusted, each of the image frames previous to the ith image frame having a respective brightness ratio which relates to the gray scale levels been determined of said one image frame and is within an allowable range, a plurality of gains which each corresponds to one of the brightness ratios varying within the allowable range being previously provided, said method comprising the following steps of:

(a)retrieving all of the gray scale levels of all pixels of the ith image frame;

(b)calculating a current brightness ratio according to all of the gray scale levels of all pixels of the ith image frame;

(c)calculating an averaged brightness ratio according to all of the brightness ratios of the image frames previous to the ith image frame and the current brightness ratio;

(d)receiving the current brightness ratio and the averaged brightness ratio;

(e)outputting one selected from the current brightness ratio or the averaged brightness ratio as an outputted brightness ratio, wherein the outputted brightness ratio is also within the allowable range;

(f)storing the brightness ratios varying within the allowable range and the corresponding gains, receiving the outputted brightness ratio, and determining the gain corresponding to the outputted brightness ratio; and

(g)receiving the gain corresponding to the outputted brightness ratio, and multiplying the gray scale level of each color component of the ith image by the gain corresponding to the outputted brightness ratio, respectively.

8. The method of claim 7, wherein the M color components are R, G, and B (Red, Green, and Blue) color components respectively conforming to RGB color space.

9. The method of claim 8, wherein the current brightness ratio BR_i is calculated by the first calculating module via the following equation:

${\mathrm{BR}}_i=\frac{Y_i}{Y_{\mathrm{total}}};<br><br>$

wherein Y_i represents the sum of all of the gray scale levels of all pixels of the ith image frame, and Y_total represents a pre-defined sum of all of the gray scale levels of all pixels of each image frame.

10. The method of claim 9, wherein the sum of all of the gray scale levels of all pixels of the ith image frame Y_i is calculated via the following equation:

$Y_i=0.3<br><br>\underset{j=1}{\overset{L}{\sum <br><br>}}<br><br>{\mathrm{GR}}_j+0.59<br><br>\underset{j=1}{\overset{L}{\sum <br><br>}}<br><br>{\mathrm{GG}}_j+0.11<br><br>\underset{j=1}{\overset{L}{\sum <br><br>}}<br><br>{\mathrm{GB}}_j$

wherein GR_j represents the gray scale level of the R color component of the jth pixel of the ith image frame, GG_j represents the gray scale level of the G color component of the jth pixel of the ith image frame, and GB_j represents the gray scale level of the B color component of the jth pixel of the ith image frame, and j is an integer index ranging from 1 to T.

11. The method of claim 10, wherein the averaged brightness ratio BR_avg is calculated by the second calculating module via the following equation:

${\mathrm{BR}}_{\mathrm{avg}}=\frac{1}{i}<br><br>\underset{k=1}{\overset{i}{\sum <br><br>}}<br><br>{\mathrm{BR}}_k;<br><br>$

12. The method of claim 11, wherein the step (e) further comprising the following steps of:

(e1)judging whether the difference between the current brightness ratio and the averaged brightness ratio is larger than the threshold;

(e2)if YES in step (e1), outputting the current brightness ratio as the outputted brightness ratio and replacing all of the brightness ratios of the image frames previous to the ith image frame by the current brightness ratio of the ith image frame; and

(e3)if NO in step (e1), outputting the averaged brightness ratio as the outputted brightness ratio.

13. In a display system, an inputted video sequence comprising N image frames to be displayed which each consists of T pixels, each pixel of each image frame being converted to comprise M color components and a luminance component, N, T, and M being a natural number, respectively, an apparatus functioning adjusting the luminance of the luminance component of the ith image frame in the video sequence, i being an integer index ranging from 1 to N, the luminance of the image frames previous to the ith image frame having been adjusted, each of the image frames previous to the ith image frame having a respective luminance ratio which relates to the luminance been determined of said one image frame and is within an allowable range, a plurality of gains which each corresponds to one of the luminance ratios varying within the allowable range being previously provided, said apparatus comprising:

a first calculating module for retrieving all of the luminance of all pixels of the ith image frame, and calculating, according to all of the luminance of all pixels of the ith image frame, a current luminance ratio;

a second calculating module for calculating, according to all of the luminance ratios of the image frames previous to the ith image frame and the current luminance ratio, an averaged luminance ratio;

a judging module for receiving the current luminance ratio and the averaged luminance ratio, and outputting one selected from the current luminance ratio or the averaged luminance ratio as an outputted luminance ratio, wherein the outputted luminance ratio is also within the allowable range;

a determining module for storing the luminance ratios varying within the allowable range and the corresponding gains, the determining module having an input coupled to receive the outputted luminance ratio, the determining module also functioning determining the gain corresponding to the outputted luminance ratio; and

an adjusting module for receiving the gain corresponding to the outputted luminance ratio, and multiplying the luminance of each luminance component of the ith image by the gain corresponding to the outputted luminance ratio, respectively.

14. The apparatus of claim 13, wherein the M color components and the luminance component conform to L*a*b* color space.

15. The apparatus of claim 14, wherein the current luminance ratio LR_i is calculated by the first calculating module via the following equation:

${\mathrm{LR}}_i=\frac{L_i}{L_{\mathrm{total}}};<br><br>$

wherein L_i represents the sum of all of the luminance of all pixels of the ith image frame, and L_total represents a pre-defined sum of all of the luminance of all pixels of each image frame.

16. The apparatus of claim 15, wherein the averaged luminance ratio LR_avg is calculated by the second calculating module via the following equation:

${\mathrm{LR}}_{\mathrm{avg}}=\frac{1}{i}<br><br>\underset{k=1}{\overset{i}{\sum <br><br>}}<br><br>{\mathrm{LR}}_k;<br><br>$

17. The apparatus of claim 16, wherein the judging module further stores a threshold, when the difference between the current luminance ratio and the averaged luminance ratio is larger than the threshold, the judging module outputs the current luminance ratio as the outputted luminance ratio and replaces all of the luminance ratios of the image frames previous to the ith image frame by the current luminance ratio of the ith image frame, and when the difference between the current luminance ratio and the averaged luminance ratio is smaller than the threshold, the judging module outputs the averaged luminance ratio as the outputted luminance ratio.

18. In a display system, an inputted video sequence comprising N image frames to be displayed which each consists of T pixels, each pixel of each image frame being converted to comprise M color components and a luminance component, N, T, and M being a natural number, respectively, a method functioning adjusting the luminance of the luminance component of the ith image frame in the video sequence, i being an integer index ranging from 1 to N, the luminance of the image frames previous to the ith image frame having been adjusted, each of the image frames previous to the ith image frame having a respective luminance ratio which relates to the luminance been determined of said one image frame and is within an allowable range, a plurality of gains which each corresponds to one of the luminance ratios varying within the allowable range being previously provided, said apparatus comprising:

(a)retrieving all of the luminance of all pixels of the ith image frame

(b)calculating a current luminance ratio according to all of the luminance of all pixels of the ith image frame;

(c)calculating an averaged luminance ratio according to all of the luminance ratios of the image frames previous to the ith image frame and the current luminance ratio;

(d)receiving the current luminance ratio and the averaged luminance ratio

(e)outputting one selected from the current luminance ratio or the averaged luminance ratio as an outputted luminance ratio, wherein the outputted luminance ratio is also within the allowable range;

(f)storing the luminance ratios varying within the allowable range and the corresponding gains, receiving the outputted luminance ratio, and determining the gain corresponding to the outputted luminance ratio; and

(g)receiving the gain corresponding to the outputted luminance ratio, and multiplying the luminance of each luminance component of the ith image by the gain corresponding to the outputted luminance ratio, respectively.

19. The method of claim 18, wherein the M color components and the luminance component conform to L*a*b* color space.

20. The apparatus of claim 19, wherein the current luminance ratio LR_i is calculated by the first calculating module via the following equation:

${\mathrm{LR}}_i=\frac{L_i}{L_{\mathrm{total}}};<br><br>$

wherein L_i represents the sum of all of the luminance of all pixels of the ith image frame, and L_total represents a pre-defined sum of all of the luminance of all pixels of each image frame.

21. The apparatus of claim 20, wherein the averaged luminance ratio LR_avg is calculated by the second calculating module via the following equation:

${\mathrm{LR}}_{\mathrm{avg}}=\frac{1}{i}<br><br>\underset{k=1}{\overset{i}{\sum <br><br>}}<br><br>{\mathrm{LR}}_k;<br><br>$

22. The apparatus of claim 21, wherein the step (e) further comprising the following steps of:

(e1)judging whether the difference between the current luminance ratio and the averaged luminance ratio is larger than the threshold;

(e2)if YES in step (e1), outputting the current luminance ratio as the outputted luminance ratio and replacing all of the luminance ratios of the image frames previous to the ith image frame by the current luminance ratio of the ith image frame; and

(e3)if NO in step (e1), outputting the averaged luminance ratio as the outputted luminance ratio.