CanvasRenderingContext2D.createRadialGradient()

The CanvasRenderingContext2D.createRadialGradient() method of the Canvas 2D API creates a radial gradient given by the coordinates of the two circles represented by the parameters. This method returns a CanvasGradient.

Syntax

CanvasGradient ctx.createRadialGradient(x0, y0, r0, x1, y1, r1);

Parameters

x0

The x axis of the coordinate of the start circle.

y0

The y axis of the coordinate of the start circle.

r0

The radius of the start circle.

x1

The x axis of the coordinate of the end circle.

y1

The y axis of the coordinate of the end circle.

r1

The radius of the end circle.

Return value

CanvasGradient

A radial CanvasGradient initialized with the two specified circles.

Examples

Using the createRadialGradient method

This is just a simple code snippet which uses the createRadialGradient method to create a CanvasGradient with the specified start and end circles. Once created, you can use the CanvasGradient.addColorStop() method to define new stops on the gradient with specified offsets and colors. The gradient gets applied if you set it as the current fillStyle and gets drawn onto the canvas when using the fillRect() method, for example.

HTML

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

JavaScript

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

var gradient = ctx.createRadialGradient(100,100,100,100,100,0);
gradient.addColorStop(0,"white");
gradient.addColorStop(1,"green");
ctx.fillStyle = gradient;
ctx.fillRect(0,0,200,200);

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

<canvas id="canvas" width="400" height="200" class="playable-canvas"></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">
var gradient = ctx.createRadialGradient(100,100,100,100,100,0);
gradient.addColorStop(0,"white");
gradient.addColorStop(1,"green");
ctx.fillStyle = gradient;
ctx.fillRect(0,0,200,200);</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

Gecko-specific notes

• Starting Gecko 2.0 (Firefox 4 / Thunderbird 3.3 / SeaMonkey 2.1), specifying non-finite values now throws NOT_SUPPORTED_ERR instead of SYNTAX_ERR.
• Starting Gecko 5.0 (Firefox 5.0 / Thunderbird 5.0 / SeaMonkey 2.2), specifying a negative radius correctly throws INDEX_SIZE_ERR.

See also

• The interface defining it, CanvasRenderingContext2D
• CanvasRenderingContext2D.createLinearGradient()