CanvasRenderingContext2D.arc()

Questo contenuto viene visualizzato in inglese perché non è ancora disponibile una versione tradotta nella lingua selezionata. Aiutaci a tradurre questo articolo!

The CanvasRenderingContext2D.arc() method of the Canvas 2D API adds a circular arc to the current sub-path.

Syntax

void ctx.arc(x, y, radius, startAngle, endAngle [, anticlockwise]);

The arc() method creates a circular arc centered at (x, y) with a radius of radius. The path starts at startAngle, ends at endAngle, and travels in the direction given by anticlockwise (defaulting to clockwise).

Parameters

x
The horizontal coordinate of the arc's center.
y
The vertical coordinate of the arc's center.
radius
The arc's radius. Must be positive.
startAngle
The angle at which the arc starts in radians, measured from the positive x-axis.
endAngle
The angle at which the arc ends in radians, measured from the positive x-axis.
anticlockwise Optional
An optional Boolean. If true, draws the arc counter-clockwise between the start and end angles. The default is false (clockwise).

Examples

Drawing a full circle

This example draws a complete circle with the arc() method.

HTML

<canvas></canvas>

JavaScript

The arc is given an x-coordinate of 100, a y-coordinate of 75, and a radius of 50. To make a full circle, the arc begins at an angle of 0 radians (0°), and ends at an angle of 2π radians (360°).

const canvas = document.querySelector('canvas');
const ctx = canvas.getContext('2d');

ctx.beginPath();
ctx.arc(100, 75, 50, 0, 2 * Math.PI);
ctx.stroke();

Result

Different shapes demonstrated

This example draws various shapes to show what is possible with arc().

const canvas = document.querySelector('canvas');
const ctx = canvas.getContext('2d');

// Draw shapes
for (let i = 0; i <= 3; i++) {
  for (let j = 0; j <= 2; j++) {
    ctx.beginPath();
    let x             = 25 + j * 50;                 // x coordinate
    let y             = 25 + i * 50;                 // y coordinate
    let radius        = 20;                          // Arc radius
    let startAngle    = 0;                           // Starting point on circle
    let endAngle      = Math.PI + (Math.PI * j) / 2; // End point on circle
    let anticlockwise = i % 2 == 1;                  // Draw anticlockwise

    ctx.arc(x, y, radius, startAngle, endAngle, anticlockwise);

    if (i > 1) {
      ctx.fill();
    } else {
      ctx.stroke();
    }
  }
}

Result

ScreenshotLive sample

Specifications

Specification Status Comment
HTML Living Standard
The definition of 'CanvasRenderingContext2D.arc' in that specification.
Living Standard

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
arcChrome Full support YesEdge Full support 12Firefox Full support 1.5IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yes

Legend

Full support  
Full support

See also