引用：

1.Drawable—>Bitmap

Resources res=getResources();

Bitmap bmp=BitmapFactory.decodeResource(res, R.drawable.sample_0);

2.Bitmap---->Drawable

Drawable drawable =new BitmapDrawable(bmp);

另外在网上搜了些，也不知到底谁是原创的

1、Drawable → Bitmap

public static Bitmap drawableToBitmap(Drawable drawable) {       

        Bitmap bitmap = Bitmap.createBitmap(

                                        drawable.getIntrinsicWidth(),

                                        drawable.getIntrinsicHeight(),

                                        drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888

                                                        : Bitmap.Config.RGB_565);

        Canvas canvas = new Canvas(bitmap);

        //canvas.setBitmap(bitmap);

        drawable.setBounds(0, 0, drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight());

        drawable.draw(canvas);

        return bitmap;

}

2、从资源中获取Bitmap

Resources res=getResources();

Bitmap bmp=BitmapFactory.decodeResource(res, R.drawable.pic);

3、Bitmap → byte[]

private byte[] Bitmap2Bytes(Bitmap bm){

    ByteArrayOutputStream baos = new ByteArrayOutputStream();

    bm.compress(Bitmap.CompressFormat.PNG, 100, baos);

    return baos.toByteArray();   }

4、 byte[] → Bitmap

   private Bitmap Bytes2Bimap(byte[] b){

                    if(b.length!=0){

                            return BitmapFactory.decodeByteArray(b, 0, b.length);

                    }

                    else {

                            return null;

                    }

          }