System and method for image luminance transformation

• US 7,126,610 B2
• Filed: 07/28/2004
• Issued: 10/24/2006
• Est. Priority Date: 07/28/2004
• Status: Expired due to Fees

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Hammond, Scott G.
• Primary Examiner(s): Bella, Matthew C.
• Assistant Examiner(s): Sajous, Wesner
• Application Number:
  US10/901,847
• Publication Number:
  US 20060022993A1
• Time in Patent Office: 818 Days
• Field of Search: 345589-594, 345/597, 345600-604, 348 70- 71, 348/496, 348/502, 348/498, 348/514, 348/520, 348/527, 348/557, 348/577, 348/582, 348602-603, 348/612, 348/655, 348/677, 348/679, 382162-167, 358515-520, 358/527
• US Class Current: 345/589
• CPC Class Codes: H04N 1/6027 Correction or control of colour gradation or colour contrast H04N1/6058 takes precedence

Abstract

An image conversion system for altering an image to adjust the overall brightness of the image when displayed is provided. The image conversion system includes a luminance transformer and a color adjuster. To adjust the overall brightness of the image, the luminance transformer reverses the luminance of each original color in the image. The new luminance of each transformed color is then compared to the desired luminance for that color. When the transformed colors do not have the desired luminance, the color adjuster modifies the hues of transformed color to achieve the desired luminance. Specifically, the color adjuster modifies the transformed color using a weighted average to achieve the desired luminance while maintaining the hues of the original color to the extent possible. By substituting each original color with a transformed color that is adjusted as needed to reach the desired luminance, the overall brightness of the image is adjusted.

Claims

1. An image conversion system for altering an image to adjust the overall brightness of the image when displayed, the image conversion system comprising:

a luminance transformer, the luminance transformer receiving image data, the luminance transformer transforming each original color in the image data to a transformed color having a new luminance, the new luminance selected to be at least proximate to a desired luminance while maintaining hues of the original color; and

a color adjuster, the color adjuster modifying the transformed color to achieve the desired luminance in the transformed color if the new luminance does not equal the desired luminance, and wherein the color adjuster modifies the transformed color using a weighted sum of the transformed color and a brightest color.

2. The system of claim 1 wherein the luminance transformer selects the new luminance to be as close as possible to the desired luminance within constraints of an image display system while maintaining hues of the original color.

3. The system of claim 1 wherein the luminance transformer selects each transformed color to have a maximum allowed value for at least one color component if the new luminance for the transformed color does not have the desired luminance for the transformed color.

4. The system of claim 1 wherein the luminance transformer selects each transformed color according to the equation

$T=S·$

min ⁡

( d l , min ⁡

( m 0 s 0 , m 1 s 1 , …

⁢

⁢

m n - 1 s n - 1 ) )

where T is a vector representation of the transformed color, S is a vector representation of the original color, d is the desired luminance of the transformed color, l is a luminance of the original color, m₀–

m<sub>n−

1</sub> are maximum color component values, and s₀–

s<sub>n−

1</sub> are color component values for the original color.

6. The system of claim 1 wherein the luminance transformer further performs a gamma correction for each original color to increase separation among relatively low luminance original colors.

7. The system of claim 1 wherein the luminance transformer calculates an original luminance for each original color, and wherein the luminance transformer performs a gamma correction on each calculated original luminance, and wherein the desired luminance for each transformed color is calculated by subtracting the gamma corrected original luminance for a corresponding original color from a maximum luminance.

8. The system of claim 1 wherein the luminance transformer calculates an original luminance for each original color, and wherein the luminance transformer performs a gamma correction on each calculated original luminance, and wherein luminance transformer calculates a reverse luminance for each original color by subtracting the gamma corrected original luminance for each original color from a maximum luminance, and wherein the luminance transformer calculates the desired luminance for each transformed color by performing a second gamma correction on the reverse luminance for each original color.

11. The system of claim 1 wherein the image conversion system creates a table to facilitate color substitution of the original colors with the transformed colors.

12. The system of claim 1 wherein the image conversion system is part of an avionics display system.

13. The system of claim 1 wherein the image data comprises map data.

5. An image conversion system for altering an image to adjust the overall brightness of the image when displayed, the image conversion system comprising:

a luminance transformer, the luminance transformer receiving image data, the luminance transformer transforming each original color in the image data to a transformed color having a new luminance, the new luminance selected to be at least proximate to a desired luminance while maintaining hues of the original color, wherein the desired luminance for each transformed color is calculated by subtracting an original luminance for a corresponding original color from a maximum luminance; and

a color adjuster, the color adjuster modifying the transformed color to achieve the desired luminance in the transformed color if the new luminance does not equal the desired luminance.

9. The system of claim 5 wherein the color adjuster modifies the transformed color using a weighted sum of the transformed color and a brightest color.

10. The system of claim 5 wherein the color adjuster modifies the transformed color by multiplying the transformed color by a weight factor k, and adding (1−

k) times a brightest color, where the factor k is defined as;

$k=\frac{m-d}{m-t},$

where

m is a maximum luminance, d is the desired luminance, and t is the new luminance.

14. A method of converting an image to adjust overall brightness of the image when displayed, the method comprising the steps of:

a) receiving image data defining the image, the image data including a plurality of original colors;

b) transforming each of the plurality of colors to a corresponding one of a plurality of transformed colors, each of the plurality of transformed colors having a new luminance at least proximate a corresponding desired luminance;

c) comparing the new luminance of each of the plurality of transformed colors to its corresponding desired luminance;

d) selectively modifying any of the plurality of transformed colors that do not have the corresponding desired luminance to achieve the desired corresponding luminance, wherein the step of selectively modifying any of the plurality of transformed colors that do not have the corresponding desired luminance to achieve the desired corresponding luminance comprises modifying using a weighted sum of the transformed color and a brightest color; and

e) displaying the image using the plurality of transformed colors as selectively modified.

15. The method of claim 14 wherein the new luminance for each of the plurality of transformed colors is selected to be as close as possible to the corresponding desired luminance within constraints of an image display system while maintaining hues of the corresponding original color.

16. The method of claim 14 wherein the step of transforming each of the plurality of colors to a corresponding one of a plurality of transformed colors comprises selecting the plurality of transformed colors to have a maximum allowed value for at least one color component if the new luminance for the transformed color does not equal the desired luminance for the transformed color.

17. The method of claim 14 wherein the step of transforming each of the plurality of colors to a corresponding one of a plurality of transformed colors comprises selecting each transformed color according to the equation

$T=S·$

min ⁡

( d l , min ⁡

( m 0 s 0 , m 1 s 1 , …

⁢

⁢

m n - 1 s n - 1 ) )

where T is a vector representation of the transformed color, S is a vector representation of the original color, d is the desired luminance of the transformed color, l is a luminance of the original color, m₀–

m<sub>n−

1</sub> are maximum color component values, and s₀–

s<sub>n−

1</sub> are color component values for the original color.

19. The method of claim 14 further comprising the step of performing a gamma correction for each original color to increase separation among relatively low luminance original colors.

20. The method of claim 14 further comprising the step of calculating an original luminance for each original color, and further comprising the step of performing a gamma correction on each calculated original luminance, and further comprising the step of calculating the desired luminance for each transformed color by subtracting the gamma corrected original luminance for a corresponding original color from a maximum luminance.

21. The method of claim 14 further comprising the step of calculating an original luminance for each original color, and further comprising the step of performing a gamma correction on each calculated original luminance, and further comprising the step of calculating a reverse luminance for each transformed color by subtracting the gamma corrected original luminance for a corresponding original color from a maximum luminance, and wherein the desired luminance for each transformed color is calculated by performing a second gamma correction on the reverse luminance for each original color.

24. The method of claim 14 further comprising the step of creating a table to facilitate color substitution of the original colors with the transformed colors.

25. The method of claim 14 wherein the step of displaying the image using the plurality of transformed colors as selectively modified comprises displaying on an avionics display system.

26. The method of claim 14 wherein image data comprises map data.

18. A method of converting an image to adjust overall brightness of the image when displayed, the method comprising the steps of:

a) receiving image data defining the image, the image data including a plurality of original colors;

b) transforming each of the plurality of colors to a corresponding one of a plurality of transformed colors, each of the plurality of transformed colors having a new luminance at least proximate a corresponding desired luminance;

c) selecting a desired luminance for each transformed color, wherein the desired luminance for each transformed color is calculated by subtracting an original luminance for a corresponding original color from a maximum luminance;

d) comparing the new luminance of each of the plurality of transformed colors to its corresponding desired luminance;

e) selectively modifying any of the plurality of transformed colors that do not have the corresponding desired luminance to achieve the desired corresponding luminance; and

f) displaying the image using the plurality of transformed colors as selectively modified.

22. The method of claim 18 wherein the step of selectively modifying any of the plurality of transformed colors that do not have the corresponding desired luminance to achieve the desired corresponding luminance comprises modifying using a weighted sum of the transformed color and a brightest color.

23. The method of claim 18 wherein the step of selectively modifying any of the plurality of transformed colors that do not have the corresponding desired luminance to achieve the desired corresponding luminance comprises multiplying the transformed color by a weight factor k, and adding (1−

k) times a brightest color, where the factor k is defined as;

$k=\frac{m-d}{m-t},$

where

m is a maximum luminance, d is the desired luminance, and t is the new luminance.

27. A program product comprising:

a) an image conversion program for altering an image to adjust the overall brightness of the image when displayed, the image conversion program comprising;

a luminance transformer, the luminance transformer receiving image data, the luminance transformer transforming each original color in the image data to a transformed color having a new luminance, the new luminance selected to be at least proximate to a desired luminance while maintaining hues of the original color; and

a color adjuster, the color adjuster modifying the transformed color to achieve the desired luminance in the transformed color if the new luminance does not equal the desired luminance, and wherein the color adjuster modifies the transformed color using a weighted sum of the transformed color and a brightest color; and

b) computer-readable signal bearing media bearing said image conversion program.

28. The program product of claim 27 wherein the computer-readable signal bearing media comprises recordable media.

29. The program product of claim 27 wherein the computer-readable signal bearing media comprises transmission media.

30. The program product of claim 27 wherein the luminance transformer selects the new luminance to be as close as possible to the desired luminance within constraints of an image display system while maintaining hues of the original color.

31. The program product of claim 27 wherein the luminance transformer selects each transformed color to have a maximum allowed value for at least one color component if the new luminance for the transformed color does not have the desired luminance for the transformed color.

33. The program product of claim 27 wherein the luminance transformer selects each transformed color according to the equation

$T=S·$

min ⁡

( d l , min ⁡

( m 0 s 0 , m 1 s 1 , …

⁢

⁢

m n - 1 s n - 1 ) )

where T is a vector representation of the transformed color, S is a vector representation of the original color, d is the desired luminance of the transformed color, l is a luminance of the original color, m₀–

m<sub>n−

1</sub> are maximum color component values, and s₀–

s<sub>n−

1</sub> are color component values for the original color.

34. The program product of claim 27 wherein the luminance transformer further performs a gamma correction for each original color to increase separation among relatively low luminance original colors.

35. The program product of claim 27 wherein the luminance transformer calculates an original luminance for each original color, and wherein the luminance transformer performs a gamma correction on each calculated original luminance, and wherein the desired luminance for each transformed color is calculated by subtracting the gamma corrected original luminance for a corresponding original color from a maximum luminance.

36. The program product of claim 27 wherein the luminance transformer calculates an original luminance for each original color, and wherein the luminance transformer performs a gamma correction on each calculated original luminance, and wherein luminance transformer calculates a reverse luminance for each original color by subtracting the gamma corrected original luminance for each original color from a maximum luminance, and wherein the luminance transformer calculates the desired luminance for each transformed color by performing a second gamma correction on the reverse luminance for each original color.

39. The program product of claim 27 wherein the image conversion system creates a table to facilitate color substitution of the original colors with the transformed colors.

40. The program product of claim 27 wherein the image conversion system is part of an avionics display system.

41. The program product of claim 27 wherein the image data comprises map data.

32. A program product comprising:

a) an image conversion program for altering an image to adjust the overall brightness of the image when displayed, the image conversion program comprising;

a luminance transformer, the luminance transformer receiving image data, the luminance transformer transforming each original color in the image data to a transformed color having a new luminance, the new luminance selected to be at least proximate to a desired luminance while maintaining hues of the original color, and wherein the desired luminance for each transformed color is calculated by subtracting an original luminance for a corresponding original color from a maximum luminance; and

a color adjuster, the color adjuster modifying the transformed color to achieve the desired luminance in the transformed color if the new luminance does not equal the desired luminance; and

b) computer-readable signal bearing media bearing said image conversion program.

37. The program product of claim 32 wherein the color adjuster modifies the transformed color using a weighted sum of the transformed color and a brightest color.

38. The program product of claim 32 wherein the color adjuster modifies the transformed color by multiplying the transformed color by a weight factor k, and adding (1−

k) times a brightest color, where the factor k is defined as;

$k=\frac{m-d}{m-t},$

where

m is a maximum luminance, d is the desired luminance, and t is the new luminance.

42. An image conversion system for altering an image of a map in an avionics display, the image conversion system selectively reducing overall brightness of the image when displayed on the avionics display, the image conversion system comprising:

a luminance transformer, the luminance transformer receiving image data of an avionics map, the luminance transformer transforming each original color in the image data to a transformed color having a new luminance, the new luminance selected to be at least proximate to a desired luminance selected to reduce the overall brightness of the image when displayed on the avionics display while maintaining hues of the original color, and wherein the desired luminance for each transformed color is calculated by subtracting an original luminance for a corresponding original color from a maximum luminance; and

a color adjuster, the color adjuster modifying the transformed color to achieve the desired luminance in the transformed color if the new luminance does not equal the desired luminance, and wherein the color adjuster modifies the transformed color using a weighted sum of the transformed color and a brightest color.

43. The system of claim 42 wherein the luminance transformer selects each transformed color according to the equation

$T=S·$

min ⁡

( d l , min ⁡

( m 0 s 0 , m 1 s 1 , …

⁢

⁢

m n - 1 s n - 1 ) )

where T is a vector representation of the transformed color, S is a vector representation of the original color, d is the desired luminance of the transformed color, l is a luminance of the original color, m₀–

m<sub>n−

1</sub> are maximum color component values, and s₀–

s<sub>n−

1</sub> are color component values for the original color, and wherein the color adjuster modifies the transformed color by multiplying the transformed color by a weight factor k, and adding (1−

k) times a brightest color, where the factor k is defined as;

$k=\frac{m-d}{m-t},$

where

m is a maximum luminance, d is the desired luminance, and t is the new luminance.