Discovered in the Android source commit is a new DPI category, XXXDHPI, which has been established for devices with a DPI of 640. According to Android engineer Dianne Hackborn, this density would typically be used for a 4K television screen which runs at 3840×2160 resolution. Like some others, you may be wondering why this would even be needed. Although the hardware and bandwidth may not be ready for such a high resolution yet, not to mention wallets and pocketbooks, the day may get here eventually and Android plans to be ready for it.
The system of DPI categories is a way for app developers to more efficiently serve up graphics and images on smartphones and tablets by providing an appropriately sized file for the device’s capabilities. The categories that exist up to now include:
- Low DPI (LDPI) – 120 DPI
- Medium DPI (MDPI) – 160 DPI (e.g. the T-Mobile G1)
- High DPI (HDPI) – 240 DPI (e.g. the Nexus S)
- Extra High DPI (XHDPI) – 320 DPI (e.g the Google Nexus 4)
- Extra Extra High DPI (XXHDPI) – 480 DPI (e.g. the HTC One)
When creating apps, developers can produce several versions of the same image and package them in the app. When a call for an image is made, the app can detect the device’s resolution and figure out which version of the image will display the best. This is especially important for low-res screens as they are probably running on lower end hardware and not only would a high-res image be a waste, it needlessly consumes memory due to the larger file size, slowing everything down in the process. On the flipside, if you have a high-res device and a low-res image gets served up to you, you might think you are using the Minecraft version of the app.
For now this probably does not mean much for the consumer. No doubt though, the race is on for ever higher screen resolutions, whether it is the current crop of TVs pushing 4K screens or whether it is a 10-inch tablet or a 5-inch smartphone. You should probably expect to see some eye-popping DPI numbers in the future.
source: Android Police