Drawable与Bitmap的相互转换

二者相互转化的代码十分简单，如下：

//Drawable--->Bitmap

public static Bitmap drawableToBitmap(Drawable drawable) {

    return ((BitmapDrawable)drawable).getBitmap();

}

//Bitmap--->Drawable

public static Drawable bitmapToDrawable(Bitmap bitmap){

    return new BitmapDrawable(bitmap);

}