---
title: CanvasRenderingContext2D.currentTransform
slug: Web/API/CanvasRenderingContext2D/currentTransform
translation_of: Web/API/CanvasRenderingContext2D/currentTransform
---
<div>{{APIRef()}} {{SeeCompatTable}}</div>

<p><code style="font-style: normal;"><strong>CanvasRenderingContext2D</strong></code><strong><code>.currentTransform</code></strong> 属性，表示当前变换的矩阵。可以通过Canvas2D API 返回或者赋值为{{domxref("SVGMatrix")}}对象。</p>

<h2 id="语法">语法</h2>

<pre class="syntaxbox"><var>ctx.currentTransform [= value];</var>
</pre>

<dl>
 <dt><code>参考</code></dt>
 <dd>{{domxref("SVGMatrix")}} 对象表示当前变换的矩阵。</dd>
</dl>

<h2 id="示例">示例</h2>

<h3 id="使用currentTransform_的方式"><code><font face="Open Sans, sans-serif">使用</font>currentTransform</code> 的方式</h3>

<p>这是一段简单的代码片段，使用<span style="font-family: consolas,monaco,andale mono,monospace;">currentTransform属性设置变换矩阵。</span></p>

<h4 id="HTML">HTML</h4>

<pre class="brush: html">&lt;canvas id="canvas"&gt;&lt;/canvas&gt;
</pre>

<h4 id="JavaScript">JavaScript</h4>

<pre class="brush: js">var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");

var matrix = ctx.currentTransform;
matrix.a = 1;
matrix.b = 1;
matrix.c = 0;
matrix.d = 1;
matrix.e = 0;
matrix.f = 0;
ctx.currentTransform = matrix;
ctx.fillRect(0,0,100,100);
</pre>

<p>修改下面的代码并在线查看canvas的变化（确定使用支持这段代码特征的浏览器，可以查看兼容性列表）:</p>

<div class="hidden">
<h6 id="Playable_code">Playable code</h6>

<pre class="brush: html">&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" style="height:150px"&gt;
var matrix = ctx.currentTransform;
matrix.a = 1;
matrix.b = 1;
matrix.c = 0;
matrix.d = 1;
matrix.e = 0;
matrix.f = 0;
ctx.currentTransform = matrix;
ctx.fillRect(0,0,100,100);&lt;/textarea&gt;
</pre>

<pre class="brush: js">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, 420) }}</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-currenttransform", "CanvasRenderingContext2D.currentTransform")}}</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>{{CompatibilityTable}}</p>

<div id="compat-desktop">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Chrome</th>
   <th>Firefox (Gecko)</th>
   <th>Internet Explorer</th>
   <th>Opera</th>
   <th>Safari</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatVersionUnknown}} [1]</td>
   <td>{{CompatNo}}<br>
    {{bug(928150)}}</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatNo}}</td>
  </tr>
 </tbody>
</table>
</div>

<div id="compat-mobile">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Android</th>
   <th>Chrome for Android</th>
   <th>Firefox Mobile (Gecko)</th>
   <th>IE Mobile</th>
   <th>Opera Mobile</th>
   <th>Safari Mobile</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatNo}}</td>
  </tr>
 </tbody>
</table>
</div>

<h3 id="Chrome-specific注解">Chrome-specific注解</h3>

<ul>
 <li>此特征默认无效。需要启用<code>ExperimentalCanvasFeatures</code> 标志进行测试。</li>
</ul>

<h2 id="参见">参见</h2>

<ul>
 <li>接口定义， {{domxref("CanvasPattern")}}</li>
 <li>{{domxref("SVGMatrix")}}</li>
</ul>