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authorPeter Bengtsson <mail@peterbe.com>2020-12-08 14:40:17 -0500
committerPeter Bengtsson <mail@peterbe.com>2020-12-08 14:40:17 -0500
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+---
+title: CanvasRenderingContext2D.getImageData()
+slug: Web/API/CanvasRenderingContext2D/getImageData
+translation_of: Web/API/CanvasRenderingContext2D/getImageData
+---
+<div>{{APIRef}}</div>
+
+<p><code><strong>CanvasRenderingContext2D</strong></code><strong><code>.getImageData()</code></strong> 返回一个{{domxref("ImageData")}}对象,用来描述canvas区域隐含的像素数据,这个区域通过矩形表示,起始点为<em>(sx, sy)、</em>宽为<em>sw、</em>高为<em>sh。</em></p>
+
+<h2 id="语法">语法</h2>
+
+<pre class="syntaxbox notranslate">ImageData <var><em>ctx</em>.getImageData(sx, sy, sw, sh);</var>
+</pre>
+
+<h3 id="参数">参数</h3>
+
+<dl>
+ <dt><code>sx</code></dt>
+ <dd>将要被提取的图像数据矩形区域的左上角 x 坐标。</dd>
+ <dt><code>sy</code></dt>
+ <dd>将要被提取的图像数据矩形区域的左上角 y 坐标。</dd>
+ <dt><code>sw</code></dt>
+ <dd>将要被提取的图像数据矩形区域的宽度。</dd>
+ <dt><code>sh</code></dt>
+ <dd>将要被提取的图像数据矩形区域的高度。</dd>
+</dl>
+
+<h3 id="返回值">返回值</h3>
+
+<p>一个{{domxref("ImageData")}} 对象,包含canvas给定的矩形图像数据。</p>
+
+<h3 id="错误抛出">错误抛出</h3>
+
+<dl>
+ <dt><code>IndexSizeError</code></dt>
+ <dd>如果高度或者宽度变量为0,则抛出错误。</dd>
+</dl>
+
+<h2 id="示例">示例</h2>
+
+<h3 id="使用_getImageData_方法">使用 <code>getImageData</code> 方法</h3>
+
+<p>这是一段使用 <code>getImageData</code> 方法的简单的代码片段。 获取更多信息,请看 <a href="/en-US/docs/Web/API/Canvas_API/Tutorial/Pixel_manipulation_with_canvas">canvas像素控制 </a>和 {{domxref("ImageData")}} 对象。</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:[6] notranslate">var canvas = document.getElementById("canvas");
+var ctx = canvas.getContext("2d");
+ctx.rect(10, 10, 100, 100);
+ctx.fill();
+
+console.log(ctx.getImageData(50, 50, 100, 100));
+// ImageData { width: 100, height: 100, data: Uint8ClampedArray[40000] }
+</pre>
+
+<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-getimagedata", "CanvasRenderingContext2D.getImageData")}}</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>
+
+
+
+<p>{{Compat("api.CanvasRenderingContext2D.getImageData")}}</p>
+
+<h3 id="兼容性注解">兼容性注解</h3>
+
+<ul>
+ <li>从 {{Gecko("5.0")}}开始, <code>getImageData()</code> 可以正确地接受超出canvas边界的矩形;canvas范围外的像素返回值是透明的,并且如果矩形小于一个像素,会返回至少一像素值的图像数据。</li>
+</ul>
+
+<h2 id="参见">参见</h2>
+
+<ul>
+ <li>接口定义, {{domxref("CanvasRenderingContext2D")}}.</li>
+ <li>{{domxref("ImageData")}}</li>
+ <li><a href="/en-US/docs/Web/API/Canvas_API/Tutorial/Pixel_manipulation_with_canvas">Pixel manipulation with canvas</a></li>
+</ul>