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Old 08-05-2011, 12:58 PM
hummrubb hummrubb is offline
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Save power with black background on Opera Mobile

I remember reading an article on here about pure black backgrounds saving power on AMOLED screens, by virtue of each pixel being powered down completely when showing black. That's nice for home screen backgrounds but I spend a lot of time surfing with Opera Mobile on the E7 (gorgeous CBD screen there ) and the default display style of showing black text on a white background definitely sucks power. The puny non-removable battery also makes things worse.

Here's how to get high contrast, white text on a black background with Opera Mobile 11 on S^3:

1. Open up opera:config in the address bar, look for Author display mode. Make sure Author CSS and Author Font and Colors are unchecked, while the other User settings are checked.

2. Look for User display mode. The settings should be the same as above.

3. Look for User prefs. The setting for Local CSS File should end in user.css, remember the full path.

4. You'll have to create the user.css file in the correct path in step #3. I connected the E7 via USB in Mass Storage mode and went to the System/Apps/Opera Mobile/styles/user folder. I then copied contrastwb.css to System/Apps/Opera Mobile/styles/user.css. This gives a basic white text/black background look which you can further edit. You could also copy the css file to another folder, as long as you change it in step #3.

Using Energy Profiler with a text-only page in Opera Mobile, I got the following values:
white text on black background: 0.26W
black text on white background: 0.34W

Interesting stuff on AMOLED vs LCD power consumption with different colors: http://forum.xda-developers.com/showthread.php?t=657702

So it actually works!
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Last edited by hummrubb; 08-05-2011 at 06:27 PM.