How do I get the WVGA Android browser to stop scaling my images?
I'm designing an HTML page for display in Android browsers. Consider this simple example page:
<html>
<head><title>Simple!</title>
</head>
<body>
<p><img src="http://sstatic.net/so/img/logo.png"></p>
</body>
</html>
It looks just fine on the standard HVGA phones (320x480), but on HDPI WVGA sizes (480x800 or 480x854) the built-in browser automatically scales the image up; it looks ugly.
I've read that I should be able to use this tag to force the browser to stop scaling my page:
<meta name="viewport" content="width=device-width; initial-scale=1.0; maximum-scale=1.0; minimum-scale=1.0; user-scalable=0;" />
... but all that does is disable user scaling (the zoom buttons disappear); it doesn't actually preven开发者_StackOverflowt the browser from scaling my image. Adjusting the scale factors (setting them all to 2.0 or 0.5) has no effect at all.
How can I force the WVGA browser to stop scaling my images?
Ah, found it by searching through the Android source code. There's a new Android-specific "target-densityDpi" setting available in the "viewport" meta tag; as far as I can tell, it's totally undocumented, except for the check-in comment!
Add dpi support for WebView.
In the "viewport" meta tag, you can specify "target-densityDpi". If it is not specified, it uses the default, 160dpi as of today. Then the 1.0 scale factor specified in the viewport tag means 100% on G1 and 150% on Sholes. If you set "target-densityDpi" to "device-dpi", then the 1.0 scale factor means 100% on both G1 and Sholes.
Implemented Safari's window.devicePixelRatio and css media query device-pixel-ratio.
So if you use "device-dpi" and modify the css for font-size and image src depending on window.devicePixelRatio, you can get a better page on Sholes/Passion.
Here is a list of options for "target-densityDpi".
device-dpi: Use the device's native dpi as target dpi. low-dpi: 120dpi medium-dpi: 160dpi, which is also the default as of today high-dpi: 240dpi : We take any number between 70 and 400 as a valid target dpi.
It's now part of the API documentation for the WebView: http://developer.android.com/reference/android/webkit/WebView.html
See the section entitled Building web pages to support different screen densities
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