ALPHA_8：Each pixel is stored as a single translucency (alpha) channel.
每个像素信息只存储了alpha这一项信息。
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.
这个值在level 13的时候就已经不被建议使用了，因为他是一个低质量的配置，它被建议使用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.
每个像素信息占用4个字节（即32个二进制位）的存储空间，alpha、red、green、blue各占8个二进制位。这个配置项是非常灵活，并提供了最好的质量。他应该在可能的情况下尽量被使用。
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
每个像素信息占用2个字节（即16位二进制位）并且至存储了RGB的信息没有alpha信息，其中Red5位，Green6位，Blue5位。这个配置项在不需要提供透明度的情况下更有用。
480*800分辨率占用的内存空间是：480*800*4/(1024*1024)=1.5M