title: set origin coordinates for react-konva stage
body: <p>I am using <code>react-konva</code> for drawing purposes. I have configured the <code>stage</code> and I am drawing certain shapes in that <code>stage</code> container. The problem I am facing is that the origin coordinates(0,0) are at the top left of the stage container. I want the center of the stage to be the origin(0,0). Here is the present code:</p>
  
  <pre><code>&lt;Stage
    height={800}
    width={1200}
    style={{ backgroundColor: '#fff', border: 'solid'}}&gt;
    {
      this.state.circlePoints.length !== 0 &amp;&amp;
      &lt;LineComponent
        startX={1200/2}
        startY={800/2}
        endX={this.state.circlePoints[0].pointX*1.3}
        endY={this.state.circlePoints[0].pointY*1.3}
        startColor={firstCircle[0].outerColor}
        endColor={pmData[0].outerColor}
      /&gt;
    }
    &lt;CircleComponent
      x={1200/2}
      y={800/2}
      outerRadius={firstCircle[0].weight*1200}
      outerColor={firstCircle[0].outerColor}
      innerRadius={firstCircle[0].weight*1200*0.3}
      innerColor={firstCircle[0].innerColor}
      shadowColor={firstCircle[0].innerColor}
      getCirclePoints={this.getCirclePoints}
    /&gt;
    {
      this.state.circlePoints.length !== 0 &amp;&amp;
      &lt;CircleComponent
        x={this.state.circlePoints[0].pointX*1.3}
        y={this.state.circlePoints[0].pointY*1.3}
        outerRadius={pmData[0].weight*1200}
        outerColor={pmData[0].outerColor}
        innerRadius={pmData[0].weight*1200*0.3}
        innerColor={pmData[0].innerColor}
        shadowColor={pmData[0].innerColor}
      /&gt;
    }
  &lt;/Stage&gt;
  </code></pre>