Canvas-2D-Context-API-Primer/arcTo.html at master · rroa/Canvas-2D-Context-API-Primer · GitHub

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<!DOCTYPE html>
<html>
    <head>
      <title>Canvas 2D Context API Primer</title>
      <meta charset="utf-8" />
      <meta name="viewport" content="width=1024" />
      <meta name="apple-mobile-web-app-capable" content="yes" />

       <!--SCRIPTS-->
      <script type="text/javascript">
        /*
          # Context 2d API: arcTo
          Draws an arc of a fixed radius between two tangents that are defined by the current point in a path and two additional points.

          # Standard Definition.
          http://www.w3.org/html/wg/drafts/2dcontext/html5_canvas/#dom-context-2d-arcto

          # Function signature
          void arcTo(unrestricted double x1, unrestricted double y1, unrestricted double x2, unrestricted double y2, unrestricted double radius);

        */

        function draw(){
          // Get a reference to the canvas
          var canvas = document.getElementById('canvas');

          // Get a reference to the drawing context
          var ctx = canvas.getContext('2d');

          // Drawing tangents

          ctx.beginPath();
          ctx.lineWidth = "3";
          ctx.strokeStyle = "black";

          // Horizontal line
          ctx.moveTo(80, 100);
          ctx.lineTo(240, 100);

          // Vertical line
          ctx.moveTo(200, 60);
          ctx.lineTo(200, 220);

          // Draw the lines
          ctx.stroke();

          ctx.beginPath();
          ctx.strokeStyle = "red";
          ctx.lineWidth = "5";

          ctx.moveTo(120, 100);

          // Horizontal line
          ctx.lineTo(180, 100);   // Draw a horizontal line.

          // Draw an arc to connect the horizontal and the vertical line
          ctx.arcTo(200, 100, 200, 120, 20);

          // Vertical line
          ctx.lineTo(200, 180);    // Continue with a vertical line of the rectangle.

          // Draw the lines
          ctx.stroke();

          // Use the translate method to move the second example down.
          ctx.translate(0, 220);
        }
      </script>
  </head>
  <body onload="draw();">
    <p>
      <a href="index.html">Back to index</a>
    </p>
    <canvas id="canvas" width="600" height="300">
      This browser or document mode doesn't support canvas
    </canvas>
  </body>
</html>