set origin coordinates for react-konva stage

问题

I am using react-konva for drawing purposes. I have configured the stage and I am drawing certain shapes in that stage 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:

<Stage
  height={800}
  width={1200}
  style={{ backgroundColor: '#fff', border: 'solid'}}>
  {
    this.state.circlePoints.length !== 0 &&
    <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}
    />
  }
  <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}
  />
  {
    this.state.circlePoints.length !== 0 &&
    <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}
    />
  }
</Stage>

回答1:

Use the layer offset command to re-position the layer on the stage. In the example below you can see that I add the x and y axis then offset the layer 200px in to the page. Finally I draw a circle on the layer at (0,0) to confirm that the layer co-ordinates remain based on this location so that you do not have to do any translation on your drawing co-ordinates.

var stage = new Konva.Stage({
      container: 'container',
      width: 600,
      height: 400
    });

var layer = new Konva.Layer();
stage.add(layer)

var axisX = new Konva.Line({
      points: [-200, 0, 200, 0],
      stroke: 'red',
      strokeWidth: 2,
      lineCap: 'round',
      lineJoin: 'round'
    });
  
var axisY = new Konva.Line({
      points: [0, 200, 0, -200],
      stroke: 'red',
      strokeWidth: 2,
      lineCap: 'round',
      lineJoin: 'round'
    });  
  
layer.add(axisX)  
layer.add(axisY)  

// offset the layer on the stage
layer.offsetX(-200)
layer.offsetY(-200)

// draw a circle at 0,0

    var circle = new Konva.Circle({
      x: 0,
      y: 0,
      radius: 70,
      stroke: 'black',
      strokeWidth: 4
    });

    // add the shape to the layer
    layer.add(circle);

layer.draw();
stage.draw();

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <title></title>
</head>
<body>
  <div id="container"></div>
            
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
    <script src="https://cdn.rawgit.com/konvajs/konva/1.7.6/konva.min.js"></script>
    <script type="text/javascript" src="test.js"></script>



</body>
</html>

回答2:

For those the above method doesn't work, do the following:

Offset Y by the stage (canvas) height
ScaleY by the negative value of your current scale. (If no scaling use -1)

eg. in react-konva

<Stage width={500} height={500} scaleY={-1} offsetY={500}>

来源：https://stackoverflow.com/questions/47305106/set-origin-coordinates-for-react-konva-stage

标签

javascript

reactjs

konvajs