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+---
+title: CanvasRenderingContext2D.textBaseline
+slug: Web/API/CanvasRenderingContext2D/textBaseline
+tags:
+ - Canvas
+ - CanvasRenderingContext2D
+translation_of: Web/API/CanvasRenderingContext2D/textBaseline
+---
+<div>{{APIRef}}</div>
+
+<p><code><strong>CanvasRenderingContext2D</strong></code><strong><code>.textBaseline</code></strong> 是 Canvas 2D API 描述绘制文本时,当前文本基线的属性。</p>
+
+<blockquote>
+<p>译者注:决定文字垂直方向的对齐方式。</p>
+</blockquote>
+
+<h2 id="语法">语法</h2>
+
+<pre class="syntaxbox"><var><em>ctx</em>.textBaseline = "top" || "hanging" || "middle" || "alphabetic" || "ideographic" || "bottom";</var>
+</pre>
+
+<h3 id="选项">选项</h3>
+
+<p>有效值:</p>
+
+<dl>
+ <dt>top</dt>
+ <dd>文本基线在文本块的顶部。</dd>
+ <dt>hanging</dt>
+ <dd>文本基线是悬挂基线。</dd>
+ <dt>middle</dt>
+ <dd>文本基线在文本块的中间。</dd>
+ <dt>alphabetic</dt>
+ <dd>文本基线是标准的字母基线。</dd>
+ <dt>ideographic</dt>
+ <dd>文字基线是表意字基线;如果字符本身超出了alphabetic 基线,那么ideograhpic基线位置在字符本身的底部。</dd>
+ <dt>bottom</dt>
+ <dd>文本基线在文本块的底部。 与 ideographic 基线的区别在于 ideographic 基线不需要考虑下行字母。</dd>
+</dl>
+
+<p>默认值是 <code>alphabetic。</code></p>
+
+<h2 id="示例">示例</h2>
+
+<h3 id="Using_the_textBaseline_property" name="Using_the_textBaseline_property">使用 <code>textBaseline</code> 属性</h3>
+
+<p>这是一段简单的代码片段,使用 <code>textBaseline</code> 属性设置不同的文本基线。</p>
+
+<h4 id="HTML">HTML</h4>
+
+<pre class="brush: html">&lt;canvas id="canvas" width="550" height="500"&gt;&lt;/canvas&gt;</pre>
+
+<h4 id="JavaScript">JavaScript</h4>
+
+<pre class="brush: js">const canvas = document.getElementById('canvas');
+const ctx = canvas.getContext('2d');
+
+const baselines = ['top', 'hanging', 'middle', 'alphabetic', 'ideographic', 'bottom'];
+ctx.font = '36px serif';
+ctx.strokeStyle = 'red';
+
+baselines.forEach(function (baseline, index) {
+ ctx.textBaseline = baseline;
+ let y = 75 + index * 75;
+ ctx.beginPath();
+ ctx.moveTo(0, y + 0.5);
+ ctx.lineTo(550, y + 0.5);
+ ctx.stroke();
+ ctx.fillText('Abcdefghijklmnop (' + baseline + ')', 0, y);
+});</pre>
+
+
+
+<div class="hidden">
+<h6 id="Playable_code" name="Playable_code">Playable code</h6>
+
+<pre class="brush: html">&lt;canvas id="canvas" width="550" height="500"&gt;&lt;/canvas&gt;</pre>
+
+<pre class="brush: js">const canvas = document.getElementById('canvas');
+const ctx = canvas.getContext('2d');
+
+const baselines = ['top', 'hanging', 'middle', 'alphabetic', 'ideographic', 'bottom'];
+ctx.font = '36px serif';
+ctx.strokeStyle = 'red';
+
+baselines.forEach(function (baseline, index) {
+ ctx.textBaseline = baseline;
+ let y = 75 + index * 75;
+ ctx.beginPath();
+ ctx.moveTo(0, y + 0.5);
+ ctx.lineTo(550, y + 0.5);
+ ctx.stroke();
+ ctx.fillText('Abcdefghijklmnop (' + baseline + ')', 0, y);
+});</pre>
+</div>
+
+<h4 id="结果">结果</h4>
+
+<p>{{ EmbedLiveSample('Playable_code', 700, 550) }}</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-textbaseline", "CanvasRenderingContext2D.textBaseline")}}</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>此页面上的兼容性表是根据结构化数据生成的。 如果您想提供数据,请查看<a href="https://github.com/mdn/browser-compat-data">https://github.com/mdn/browser-compat-data</a>并向我们发送请求请求。</p>
+</div>
+
+<p>{{Compat("api.CanvasRenderingContext2D.textBaseline")}}</p>
+
+<h2 id="参见">参见</h2>
+
+<ul>
+ <li>接口定义,{{domxref("CanvasRenderingContext2D")}}.</li>
+</ul>