ALPHA_8：Each pixel is stored as a single translucency (alpha) channel.
每個像素信息只存儲了alpha這一項信息。
ARGB_4444：This field was deprecated in API level 13. Because of the poor quality of this configuration, it is advised to use ARGB_8888 instead.
這個值在level 13的時候就已經不被建議使用了，因爲他是一個低質量的配置，它被建議使用ARGB_8888
ARGB_8888：Each pixel is stored on 4 bytes. This configuration is very flexible and offers the best quality. It should be used whenever possible.
每個像素信息佔用4個字節（即32個二進制位）的存儲空間，alpha、red、green、blue各佔8個二進制位。這個配置項是非常靈活，並提供了最好的質量。他應該在可能的情況下儘量被使用。
RGB_565：Each pixel is stored on 2 bytes and only the RGB channels are encoded: red is stored with 5 bits of precision (32 possible values), green is stored with 6 bits of precision (64 possible values) and blue is stored with 5 bits of precision.This configuration may be useful when using opaque bitmaps that do not require high color fidelity
每個像素信息佔用2個字節（即16位二進制位）並且至存儲了RGB的信息沒有alpha信息，其中Red5位，Green6位，Blue5位。這個配置項在不需要提供透明度的情況下更有用。
480*800分辨率佔用的內存空間是：480*800*4/(1024*1024)=1.5M