HTML5 canvas Spline Tutorial

To create a spline with Konva, we can instantiate a Konva.Line() object with tension attribute.

To define the path of the line you should use points property. If you have three points with x and y coordinates you should define points property as: [x1, y1, x2, y2, x3, y3].

Flat array of numbers should work faster and use less memory than array of objects.

For a full list of attributes and methods, check out the Konva.Line documentation.

Konva Spline Demoview raw

<!DOCTYPE html>
<html>
  <head>
    <script src="https://unpkg.com/[email protected]/konva.min.js"></script>
    <meta charset="utf-8" />
    <title>Konva Line Spline Demo</title>
    <style>
      body {
        margin: 0;
        padding: 0;
        overflow: hidden;
        background-color: #f0f0f0;
      }
    </style>
  </head>
  <body>
    <div id="container"></div>
    <script>
      var width = window.innerWidth;
      var height = window.innerHeight;

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

      var layer = new Konva.Layer();

      var redLine = new Konva.Line({
        points: [5, 70, 140, 23, 250, 60, 300, 20],
        stroke: 'red',
        strokeWidth: 15,
        lineCap: 'round',
        lineJoin: 'round',
        tension: 1,
      });

      // dashed line
      var greenLine = new Konva.Line({
        points: [5, 70, 140, 23, 250, 60, 300, 20],
        stroke: 'green',
        strokeWidth: 2,
        lineJoin: 'round',
        /*
         * line segments with a length of 33px
         * with a gap of 10px
         */
        dash: [33, 10],
        lineCap: 'round',
        tension: 0.5,
      });

      // complex dashed and dotted line
      var blueLine = new Konva.Line({
        points: [5, 70, 140, 23, 250, 60, 300, 20],
        stroke: 'blue',
        strokeWidth: 10,
        lineCap: 'round',
        lineJoin: 'round',
        /*
         * line segments with a length of 29px with a gap
         * of 20px followed by a line segment of 0.001px (a dot)
         * followed by a gap of 20px
         */
        dash: [29, 20, 0.001, 20],
        tension: 0.7,
      });

      /*
       * since each line has the same point array, we can
       * adjust the position of each one using the
       * move() method
       */
      redLine.move({
        x: 20,
        y: 5,
      });
      greenLine.move({
        x: 20,
        y: 55,
      });
      blueLine.move({
        x: 20,
        y: 105,
      });

      layer.add(redLine);
      layer.add(greenLine);
      layer.add(blueLine);

      // add the layer to the stage
      stage.add(layer);
    </script>
  </body>
</html>

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