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---
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"><canvas id="canvas"></canvas>
</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"><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" style="height:150px">
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);</textarea>
</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>
{{Compat("api.CanvasRenderingContext2D.currentTransform")}}
<h2 id="参见">参见</h2>
<ul>
<li>接口定义， {{domxref("CanvasPattern")}}</li>
<li>{{domxref("SVGMatrix")}}</li>
</ul>
|
