title: Fade Image.asset when SingleChildScrollView scrolls
body: <p>I have an <code>image.asset</code> at the top of a <code>Column</code> inside a <code>SingleChildScrollView</code></p>
  <p>I'm trying to achieve that when the users scrolls the scrollView, the image will fade out.</p>
  <p>I've tried to to it using the <code>controller</code> property of the scrollView, but I couldn't achieve the opacity change.</p>
  <p>Does anyone has an idea what is the most efficient way to do that?</p>
  <p>Thank you!</p>
  <p><strong>Current Code</strong>:</p>
  <pre><code>Scaffold(
        backgroundColor: Colors.white,
        body: SingleChildScrollView(
          child: Column(
            children: [
              Stack(
                children: [
                  Container(
                    height: _imageTopPosition + _imageHeight,
                    color: Colors.blue[100],
                  ),
                  Positioned(
                    top: _customShapeTopPosition,
                    child: MyCustomShape(
                      size: Size(_screenSize.width, _customShapeHeight),
                    ),
                  ),
                  Positioned(
                    top: _imageTopPosition,
                    right: _imageRightPosition,
                    child: Image.asset( //The image I would like to fade on scroll
                      'assets/images/image.png',
                      width: _imageWidth,
                      height: _imageHeight,
                    ),
                  ),
                ],
              ),
              Padding(
                padding: EdgeInsets.only(top: _screenSize.height * 0.05),
              ),
              Text('Some Text'),
            ],
          ),
        ),
      );
  </code></pre>