Adding to my comments, this is from Android Developers - multi-screen support .
Provide different bitmap patterns for different screen densities By default, Android scales your bitmap patterns (.png, .jpg and .gif) and Nine-Patch drawables (.9.png files) so that they display with the appropriate physical size on each device . For example, if your application provides bitmap drawings only for the baseline, medium screen density (mdpi), the system scales them on a high density screen and scales them on a low density screen. This scaling can cause artifacts in bitmap images. To make your bitmaps look their best, you must include alternate versions with different resolutions for different screen densities.
And from Roman Nurik post
Android 4.4 KitKat, Android. :...
7) XXXHDPI (640dpi) - Nexus 5.
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Edit
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