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---
title: CanvasRenderingContext2D.transform()
slug: Web/API/CanvasRenderingContext2D/transform
translation_of: Web/API/CanvasRenderingContext2D/transform
---
<div>{{APIRef}}</div>
<p><code><strong>CanvasRenderingContext2D</strong></code><strong><code>.transform()</code></strong> 是 Canvas 2D API 使用矩阵多次叠加当前变换的方法，矩阵由方法的参数进行描述。你可以缩放、旋转、移动和倾斜上下文。</p>
<p>参见 {{domxref("CanvasRenderingContext2D.setTransform()", "setTransform()")}} 方法，这个方法使用单位矩阵重新设置当前的变换并且会调用 <code>transform()。</code></p>
<h2 id="语法">语法</h2>
<pre class="syntaxbox">void <var><em>ctx</em>.transform(a, b, c, d, e, f);</var>
</pre>
<p>变换矩阵的描述： <math><semantics><mrow><mo>[</mo><mtable columnalign="center center center" rowspacing="0.5ex"><mtr><mtd><mi>a</mi></mtd><mtd><mi>c</mi></mtd><mtd><mi>e</mi></mtd></mtr><mtr><mtd><mi>b</mi></mtd><mtd><mi>d</mi></mtd><mtd><mi>f</mi></mtd></mtr><mtr><mtd><mn>0</mn></mtd><mtd><mn>0</mn></mtd><mtd><mn>1</mn></mtd></mtr></mtable><mo>]</mo></mrow><annotation encoding="TeX">\left[ \begin{array}{ccc} a & c & e \\ b & d & f \\ 0 & 0 & 1 \end{array} \right]</annotation></semantics></math></p>
<h3 id="参数">参数</h3>
<dl>
<dt><code>a (m11)</code></dt>
<dd>水平缩放。</dd>
<dt><em><code>b (m12)</code></em></dt>
<dd>垂直倾斜。</dd>
<dt><code>c (m21)</code></dt>
<dd>水平倾斜。</dd>
<dt><code>d (m22)</code></dt>
<dd>垂直缩放。</dd>
<dt><code>e (dx)</code></dt>
<dd>水平移动。</dd>
<dt><code>f (dy)</code></dt>
<dd>垂直移动。</dd>
</dl>
<h2 id="示例">示例</h2>
<h3 id="使用_transform_方法">使用 <code>transform</code> 方法</h3>
<p>这是一段使用 <code>transform</code> 方法的简单的代码片段。</p>
<h4 id="HTML">HTML</h4>
<pre class="brush: html"><canvas id="canvas"></canvas>
</pre>
<h4 id="JavaScript">JavaScript</h4>
<pre class="brush: js; highlight:[4]">var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
ctx.transform(1,1,0,1,0,0);
ctx.fillRect(0,0,100,100);
</pre>
<p>修改下面的代码并在线查看 canvas 的变化：</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">
ctx.transform(1,1,0,1,0,0);
ctx.fillRect(0,0,100,100);
ctx.setTransform();
</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;
ctx.setTransform(1, 0, 0, 1, 0, 0);
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-transform", "CanvasRenderingContext2D.transform")}}</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() }}</td>
<td>{{ CompatVersionUnknown() }}</td>
<td>{{ CompatVersionUnknown() }}</td>
<td>{{ CompatVersionUnknown() }}</td>
<td>{{ CompatVersionUnknown() }}</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>{{ CompatVersionUnknown() }}</td>
<td>{{ CompatVersionUnknown() }}</td>
<td>{{ CompatVersionUnknown() }}</td>
<td>{{ CompatVersionUnknown() }}</td>
<td>{{ CompatVersionUnknown() }}</td>
<td>{{ CompatVersionUnknown() }}</td>
</tr>
</tbody>
</table>
</div>
<h2 id="参见">参见</h2>
<ul>
<li>接口定义， {{domxref("CanvasRenderingContext2D")}}</li>
<li>{{domxref("CanvasRenderingContext2D.setTransform()")}}</li>
</ul>
|
