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+---
+title: CanvasRenderingContext2D.createRadialGradient()
+slug: Web/API/CanvasRenderingContext2D/createRadialGradient
+translation_of: Web/API/CanvasRenderingContext2D/createRadialGradient
+---
+<div>{{APIRef}}</div>
+
+<p><code><strong>CanvasRenderingContext2D</strong></code><strong><code>.createRadialGradient()</code></strong> 是 Canvas 2D API 根据参数确定两个圆的坐标，绘制放射性渐变的方法。这个方法返回 {{domxref("CanvasGradient")}}。</p>
+
+<h2 id="语法">语法</h2>
+
+<pre class="syntaxbox notranslate">CanvasGradient <var><em>ctx</em>.createRadialGradient(x0, y0, r0, x1, y1, r1);</var>
+</pre>
+
+<h3 id="参数">参数</h3>
+
+<dl>
+ <dt><code>x0</code></dt>
+ <dd>开始圆形的 x 轴坐标。</dd>
+ <dt><code>y0</code></dt>
+ <dd>开始圆形的 y 轴坐标。</dd>
+ <dt>r0</dt>
+ <dd>开始圆形的半径。</dd>
+ <dt><code>x1</code></dt>
+ <dd>结束圆形的 x 轴坐标。</dd>
+ <dt><code>y1</code></dt>
+ <dd>结束圆形的 y 轴坐标。</dd>
+ <dt>r1</dt>
+ <dd>结束圆形的半径。</dd>
+</dl>
+
+<h3 id="返回值">返回值</h3>
+
+<dl>
+ <dt>{{domxref("CanvasGradient")}}</dt>
+ <dd>由两个指定的圆初始化的放射性 <code>CanvasGradient</code> 对象。</dd>
+</dl>
+
+<h2 id="示例">示例</h2>
+
+<h3 id="使用_createRadialGradient_方法">使用 <code>createRadialGradient</code> 方法</h3>
+
+<p>这是一段简单的代码片段， 使用 <code>createRadialGradient</code> 方法创建一个指定了开始和结束圆的 {{domxref("CanvasGradient")}} 对象。 一旦创建，你可以使用 {{domxref("CanvasGradient.addColorStop()")}} 方法根据指定的偏移和颜色定义一个新的终止。你可以将当前的{{domxref("CanvasRenderingContext2D.fillStyle", "fillStyle")}}设置成此渐变， 当使用{{domxref("CanvasRenderingContext2D.fillRect", "fillRect()")}} 方法时，会在canvas上绘制出效果， 如示例所示。</p>
+
+<h4 id="HTML">HTML</h4>
+
+<pre class="brush: html notranslate">&lt;canvas id="canvas"&gt;&lt;/canvas&gt;
+</pre>
+
+<h4 id="JavaScript">JavaScript</h4>
+
+<pre class="brush: js; highlight:[4] notranslate">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);
+</pre>
+
+<p>修改下面的代码并在线查看 canvas的变化：</p>
+
+<div style="display: none;">
+<h6 id="Playable_code">Playable code</h6>
+
+<pre class="brush: html notranslate">&lt;canvas id="canvas" width="400" height="200" class="playable-canvas"&gt;&lt;/canvas&gt;
+&lt;div class="playable-buttons"&gt;
+  &lt;input id="edit" type="button" value="Edit" /&gt;
+  &lt;input id="reset" type="button" value="Reset" /&gt;
+&lt;/div&gt;
+&lt;textarea id="code" class="playable-code"&gt;
+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);&lt;/textarea&gt;
+</pre>
+
+<pre class="brush: js notranslate">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);
+</pre>
+</div>
+
+<p>{{ EmbedLiveSample('Playable_code', 700, 360) }}</p>
+
+<h2 id="规范描述">规范描述</h2>
+
+<table class="standard-table">
+ <tbody>
+  <tr>
+   <th scope="col">Specification</th>
+   <th scope="col">Status</th>
+   <th scope="col">Comment</th>
+  </tr>
+  <tr>
+   <td>{{SpecName('HTML WHATWG', "scripting.html#dom-context-2d-createradialgradient", "CanvasRenderingContext2D.createRadialGradient")}}</td>
+   <td>{{Spec2('HTML WHATWG')}}</td>
+   <td></td>
+  </tr>
+ </tbody>
+</table>
+
+<h2 id="浏览器兼容性">浏览器兼容性</h2>
+
+<div class="hidden">
+<p>The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out <a href="https://github.com/mdn/browser-compat-data">https://github.com/mdn/browser-compat-data</a> and send us a pull request.</p>
+</div>
+
+<p>{{Compat("api.CanvasRenderingContext2D.createRadialGradient")}}</p>
+
+<div id="compat-mobile"></div>
+
+<h3 id="Gecko-specific_注解">Gecko-specific 注解</h3>
+
+<ul>
+ <li>从 Gecko 2.0 {{geckoRelease("2.0")}}开始， 指定非限制的值会抛出 <code>NOT_SUPPORTED_ERR</code> ，用来替代 <code>SYNTAX_ERR。</code></li>
+ <li>从 Gecko 5.0 {{geckoRelease("5.0")}}开始，指定一个负的半径会抛出 <code>INDEX_SIZE_ERR。</code></li>
+</ul>
+
+<h2 id="参见">参见</h2>
+
+<ul>
+ <li>接口定义， {{domxref("CanvasRenderingContext2D")}}</li>
+ <li>{{domxref("CanvasRenderingContext2D.createLinearGradient()")}}</li>
+</ul>