RenderScript blur overrides the original Bitmap

Question

I am trying to use RenderScript to create a blurred bitmap to set it as a background for a LinearLayout which contains an ImageView . I also want a clear original copy of the bitmap so that I can set it as an image in the ImageView .

Here's my code:

ImageView mainImage;

Bitmap mainBMP, blurredBMP

LinearLayout background;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_work_area);

    getImage(); // obtain bitmap from file
    mainImage.setImageBitmap(mainBMP); // set the original bitmap in imageview 

    // create a blurred bitmap drawable and set it as background for linearlayout
    BitmapDrawable drawable = new BitmapDrawable(getResources(), blur(mainBMP)); 
    mainBackground.setBackground(drawable); 


    registerForContextMenu(objectImage);
    registerForContextMenu(textArea);

}

private void getImage(){
    String filename = getIntent().getStringExtra("image");
    try {
        FileInputStream is = this.openFileInput(filename);
        mainBMP = BitmapFactory.decodeStream(is);
        is.close();
    } catch (Exception e) {
        e.printStackTrace();
    }
}

@TargetApi(17)
public Bitmap blur(Bitmap image) {
    if (null == image) return null;

    Bitmap outputBitmap = Bitmap.createBitmap(image);
    final RenderScript renderScript = RenderScript.create(this);
    Allocation tmpIn = Allocation.createFromBitmap(renderScript, image);
    Allocation tmpOut = Allocation.createFromBitmap(renderScript, outputBitmap);

    //Intrinsic Gausian blur filter
    ScriptIntrinsicBlur theIntrinsic = ScriptIntrinsicBlur.create(renderScript, Element.U8_4(renderScript));
    theIntrinsic.setRadius(BLUR_RADIUS);
    theIntrinsic.setInput(tmpIn);
    theIntrinsic.forEach(tmpOut);
    tmpOut.copyTo(outputBitmap);
    return outputBitmap;
}

This is how I want the final result to be:

But this is what I get:

So how do I make two copies of the same bitmap in which one of them is blurred and the other is clear and original ?

Answer 1

The problem is with how the output bitmap is being created. You're using a call that gives you an immutable Bitmap object based on an input Bitmap object. Change this line:

Bitmap outputBitmap = Bitmap.createBitmap(image);

to be this:

Bitmap outputBitmap = image.copy(image.getConfig(), true);

That will give you a separate Bitmap object which is a copy of the original and mutable. Right now Renderscript is really modifying the original (though it really should fail because the outputBitmap was immutable.