In the below example code I have created blur background image function. In activity_main.xml layout I have added a Button and ImageView.

Now see programming area, here I have used Bitmap class. When a user clicks on button background image will get blur easily without any delay in time.
 See below code I have Completely described "to blur background image with using BitMap".

Step(1)-activity_main.xml-

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"

    android:id="@+id/relative"
    tools:context="com.example.androidimageview.MainActivity">


        <Button
            android:id="@+id/btn"
            android:text="Click"
            android:gravity="center"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />
    
    <ImageView

        android:id="@+id/image"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"/>

</RelativeLayout>

Step(2)-MainActivity-

public class MainActivity extends ActionBarActivity  {
    ImageView imageView;
    Button button;
    Bitmap bitmapOriginal;
    View view;

    RelativeLayout relativeLayout;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        imageView=(ImageView)findViewById(R.id.image);
        button=(Button)findViewById(R.id.btn);
        relativeLayout=(RelativeLayout)findViewById(R.id.relative);
        bitmapOriginal= BitmapFactory.decodeResource(getResources(),R.drawable.img);
   
        imageView.setBackground(getDrawable(R.drawable.one));


        button.setOnClickListener(new Button.OnClickListener() {
            @Override
            public void onClick(View v) {

               BitmapDrawable ob = new BitmapDrawable(getResources(), blur(bitmapOriginal));
                imageView.setBackground(ob);
                imageView.setImageDrawable(ob);
          }
      });


    }
     //image effect
     private static final float BITMAP_SCALE = 0.4f;
    private static final float BLUR_RADIUS = 7.5f;

    public Bitmap blur(Bitmap image) {

        int width = Math.round(image.getWidth() * BITMAP_SCALE);
        int height = Math.round(image.getHeight() * BITMAP_SCALE);

        Bitmap inputBitmap = Bitmap.createScaledBitmap(image, width, height, false);
        Bitmap outputBitmap = Bitmap.createBitmap(inputBitmap);

       //using RenderScript class
        RenderScript rs = RenderScript.create(this);
        ScriptIntrinsicBlur theIntrinsic = ScriptIntrinsicBlur.create(rs, Element.U8_4(rs));
        Allocation tmpIn = Allocation.createFromBitmap(rs, inputBitmap);
        Allocation tmpOut = Allocation.createFromBitmap(rs, outputBitmap);
        theIntrinsic.setRadius(BLUR_RADIUS);
        theIntrinsic.setInput(tmpIn);
        theIntrinsic.forEach(tmpOut);
        tmpOut.copyTo(outputBitmap);

        return outputBitmap;

    }
}