CHAMELEON

CHAMELEONTroy Ferrell

Liancheng Shen

ECE 256 – 2/26/2012

What’s the Problem?

What’s the Problem?OLED vs. LCD

OLED displays consume dramatically different power for showing different colors than LCD displaysWHY?

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

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?

Solutions/Related Work?HP Labs

Darkening display regions outside of focal area

IBM Linux WatchOnly studied GUI with two colors

Studies for energy-aware color transformation for LCD targeted for data visualization applications

Chameleon

Chameleon• A color adaptive web browser that

renders web pages with power optimized color schemes under user-supplied constraints

Important ConsiderationsOLED 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

Important ConsiderationsWeb 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 allA small number of websites account for most

web usage65% of pixels in web pages visited by 25 users

over 3 months are white

Important ConsiderationsModern web page contains visual objects of

different fidelity requirementsDivide element of web page into GUI objects &

imagesThe Clash of the Images

Important ConsiderationsUser 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

How does it work?

Key design decisionsTreat GUI Objects and Images DifferentlyKeep Color Consistency per Web siteGenerate Device Specific OLED Power ModelCalculate Color Maps OfflineGive User Options

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

ArchitectureColor-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

'E M X D

Event-driven Time Counting

Pixel Counting

Pixel Counting

Key EvaluationsHow long do user need to train chameleon

Two weeks for trainingHow well does the past predict the future?

Past predicts future wellOverhead issues & time Delay?

Minimal – on order of 10’s of milliseconds

Our Thoughts

Our ThoughtsDevise “OLED-Friendly” user setting

for mobile devices at the OS level to save battery life

Our ThoughtsOff-line mode means history not presentStatic pageReducing brightness of the foreground and

change the color of background may result in low contrast.

THE END! Questions? Qualms? Ideas? Considerations? Issues? Concerns? Inquiries? Proposals? Problems?

THANK YOU!