System and method for adjusting a backlight level for a display on an electronic device

1. A method of adjusting an output for a backlight for a display of an electronic device, comprising:

identifying a highest brightness value for a pixel in an image to be generated on the display;

determining a brightness headroom value for the image based on a difference between the highest brightness value and a maximum brightness level for the display; and

if the brightness headroom value is determined to be larger than a predetermined threshold, then when an adjusted image based on the image is generated on the display having a brightness based on a value related to a ratio of the brightness headroom to the highest brightness value, generating an adjusted backlight level for the backlight, the adjusted backlight level being based on a ratio of the highest brightness value to the maximum brightness level.

2. The method as claimed in claim 1 , wherein the highest brightness value is identified by analyzing a predefined region of the image for the highest brightness value.

3. The method as claimed in claim 2 , wherein the predefined region is selected from one of alternating rows and a central region in the display.

4. The method as claimed in claim 1 , wherein the highest brightness value is identified when a pixel in the image having the highest brightness value is within a predetermined number of pixels to another pixel in the image having a brightness that is within a predetermined range of the highest brightness value.

5. The method as claimed in claim 1 , wherein the highest brightness value is identified from a greyscale representation of the image and the greyscale representation has been adjusted according to a gamma value.

6. The method as claimed in claim 5 , wherein the greyscale representation provides a weight to favour green values in the image.

7. The method as claimed in claim 1 , further comprising adjusting the adjusted backlight level to account for ambient light conditions surrounding the device by increasing the adjusted backlight level as the ambient light conditions increase up to a certain point and deactivating the backlight the ambient conditions past the certain point.

8. The method as claimed in claim 1 , further comprising repeating the method when the image is replaced by another image on the display and the another image contains changes over the image in more than a predetermined portion of the image.

9. The method as claimed in claim 1 , wherein:

the display is displaying a video image; and

the highest brightness value is identified when a pixel in the image having the highest brightness value has a brightness value that is within a predetermined range of the highest brightness value in an image that is either before or after the image in the video image.

10. The method as claimed in claim 1 , further comprising generating the image on the display using the backlight level if the brightness headroom does not exceed the predetermined threshold.

11. The method as claimed in claim 1 , wherein in identifying the highest brightness value, the predefined region is selected from one of alternating rows and a central region in the display.

12. An electronic device, comprising:

a display for displaying images;

an image processing module to identify a highest brightness value of a pixel in an image for generation on the display and to determine a brightness headroom value for the image based on a value related to a ratio of the brightness headroom to the highest brightness value for the display;

a backlight adjustment module to provide an adjusted backlight level for the adjusted image, the adjusted backlight level being based on a ratio of the highest brightness value to a maximum brightness level for the display; and

a backlight system to provide a backlight for the display at the adjusted backlight level.

13. The electronic device as claimed in claim 12 , wherein the backlight adjustment module decreases the adjusted backlight level by a factor relating to a current backlight level for the backlight system and the brightness headroom.

14. The electronic device as claimed in claim 12 , wherein the image processing module scans at least a part of pixels in the image to identify the highest brightness value.

15. The electronic device as claimed in claim 14 , wherein the image processing module assesses whether a pixel in the image having the highest brightness value is within a preset number of pixels to another pixel having a comparable brightness before identifying the highest brightness value as being represented by the pixel.

16. The electronic device as claimed in claim 12 , wherein the image processing module identifies the highest brightness value from a greyscale representation of the image and the greyscale representation has been corrected according to a gamma curve.

17. The electronic device as claimed in claim 12 , wherein the backlight adjustment module adjusts the adjusted backlight level to account for an ambient light conditions obtained from a light sensor for the device to increase a current backlight level as the ambient light conditions increase up to a certain point and to deactivate the backlight when the ambient light conditions pass the certain point.