CanvasRenderingContext2D.arcTo

The CanvasRenderingContext2D.arcTo() method of the Canvas 2D API adds an arc to the path with the given control points and radius, connected to the previous point by a straight line.

Syntax

void ctx.arcTo(x1, y1, x2, y2, radius);

Parameters

x1

The x axis of the coordinate for the first control point.

y1

The y axis of the coordinate for the first control point.

x2

The x axis of the coordinate for the second control point.

y2

The y axis of the coordinate for the second control point.

radius

The arc's radius.

Examples

Using the arcTo method

This is just a simple code snippet drawing an arc. The base point is blue and the two control points are red.

HTML

<canvas id="canvas"></canvas>

JavaScript

var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');

ctx.beginPath();
ctx.moveTo(150, 20);
ctx.arcTo(150, 100, 50, 20, 30);
ctx.stroke();

ctx.fillStyle = 'blue';
// base point
ctx.fillRect(150, 20, 10, 10);

ctx.fillStyle = 'red';
// control point one
ctx.fillRect(150, 100, 10, 10);
// control point two
ctx.fillRect(50, 20, 10, 10);

Trying the arcTo parameters

Edit the code below and see your changes update live in the canvas:

<canvas id="canvas" class="playable-canvas" height="200" width="400"></canvas>
<div class="playable-buttons">
  <input id="edit" type="button" value="Edit" />
  <input id="reset" type="button" value="Reset" />
</div>
<textarea id="code" class="playable-code">
ctx.beginPath();
ctx.moveTo(150, 20);
ctx.arcTo(150,200,50,0,20);
ctx.stroke();</textarea>

var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var textarea = document.getElementById("code");
var reset = document.getElementById("reset");
var edit = document.getElementById("edit");
var code = textarea.value;

function drawCanvas() {
  ctx.clearRect(0, 0, canvas.width, canvas.height);
  eval(textarea.value);
}

reset.addEventListener("click", function() {
  textarea.value = code;
  drawCanvas();
});

edit.addEventListener("click", function() {
  textarea.focus();
})

textarea.addEventListener("input", drawCanvas);
window.addEventListener("load", drawCanvas);

Specifications

Browser compatibility

See also

• The interface defining it, CanvasRenderingContext2D