1. CHAMELEON Troy Ferrell Liancheng Shen ECE 256 – 2/26/2012

2. What’s the Problem?

3. What’s the Problem? OLED vs. LCD OLED displays consume dramatically different power for showing different colors than LCD displays WHY? OLED displays do not require a backlight as LCD displays do because OLED pixels, themselves, are emissive The color of an OLED pixel directly impacts it’s power consumption Displaying dark colors such as black require little if no power on OLED displays yet bright colors such as white actually consume more power on OLED displays than LCD

4. Solutions/Related Work? Web content providers solve problem by providing web pages in energy-efficient color schemes? Problem solved by configuring web browsers with most energy-efficient color scheme? Implement color transformation at mobile client?

5. Solutions/Related Work? HP Labs Darkening display regions outside of focal area IBM Linux Watch Only studied GUI with two colors Studies for energy-aware color transformation for LCD targeted for data visualization applications

6. Chameleon

7. A color adaptive web browser that renders web pages with power optimized color schemes under user-supplied constraints

8. Important Considerations OLED Display Power OLED display power model is a linear function of linear RGB intensity levels. Different displays have different power characteristics Chromaticity makes a big difference even when the lightness is identical

9. Important Considerations Web Usage Mobile users still visit web pages that are not optimized for mobile devices. ~50% of web pages visited by mobile users are not optimized for mobile devices at all A small number of websites account for most web usage 65% of pixels in web pages visited by 25 users over 3 months are white

10. Important Considerations Modern web page contains visual objects of different fidelity requirements Divide element of web page into GUI objects & images The Clash of the Images

11. Important Considerations User Preferences for Color Transformations Different users prefer different transformations for a web site Even same user may favor different color transformations for different web sites

12. How does it work?

13. Key design decisions Treat GUI Objects and Images Differently Keep Color Consistency per Web site Generate Device Specific OLED Power Model Calculate Color Maps Offline Give User Options

14. How does it work? Utilize Color Transformations! Objective of a color transformation is to find a color map, or N transformed colors to substitute the original N colors on a page so that: the display power consumption is minimized perception constraints such as fidelity and usability are met

15. Architecture Color-dependent energy consumption M is the OLED power model; X’ is a matrix called the color map D is the color contribution vector for the web site

18. Event-driven Time Counting

20. Pixel Counting

24. Key Evaluations How long do user need to train chameleon Two weeks for training How well does the past predict the future? Past predicts future well Overhead issues & time Delay? Minimal – on order of 10’s of milliseconds

25. Our Thoughts

26. Devise “OLED-Friendly” user setting for mobile devices at the OS level to save battery life

27. Our Thoughts Off-line mode means history not present Static page Reducing brightness of the foreground and change the color of background may result in low contrast.

28. THE END! Questions? Qualms? Ideas? Considerations? Issues? Concerns? Inquiries? Proposals? Problems? THANK YOU!