static get(): number {
    return Dimensions.get('window').scale;
  }
Returns the device pixel density. Some examples:

  - PixelRatio.get() === 1
    - mdpi Android devices (160 dpi)
  - PixelRatio.get() === 1.5
    - hdpi Android devices (240 dpi)
  - PixelRatio.get() === 2
    - iPhone 4, 4S
    - iPhone 5, 5c, 5s
    - iPhone 6
    - xhdpi Android devices (320 dpi)
  - PixelRatio.get() === 3
    - iPhone 6 plus
    - xxhdpi Android devices (480 dpi)
  - PixelRatio.get() === 3.5
    - Nexus 6