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| author | Peter Bengtsson <mail@peterbe.com> | 2020-12-08 14:40:17 -0500 |
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| committer | Peter Bengtsson <mail@peterbe.com> | 2020-12-08 14:40:17 -0500 |
| commit | 33058f2b292b3a581333bdfb21b8f671898c5060 (patch) | |
| tree | 51c3e392513ec574331b2d3f85c394445ea803c6 /files/zh-cn/web/api/canvasrenderingcontext2d/ellipse/index.html | |
| parent | 8b66d724f7caf0157093fb09cfec8fbd0c6ad50a (diff) | |
| download | translated-content-33058f2b292b3a581333bdfb21b8f671898c5060.tar.gz translated-content-33058f2b292b3a581333bdfb21b8f671898c5060.tar.bz2 translated-content-33058f2b292b3a581333bdfb21b8f671898c5060.zip | |
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diff --git a/files/zh-cn/web/api/canvasrenderingcontext2d/ellipse/index.html b/files/zh-cn/web/api/canvasrenderingcontext2d/ellipse/index.html new file mode 100644 index 0000000000..d46c4acb87 --- /dev/null +++ b/files/zh-cn/web/api/canvasrenderingcontext2d/ellipse/index.html @@ -0,0 +1,140 @@ +--- +title: CanvasRenderingContext2D.ellipse() +slug: Web/API/CanvasRenderingContext2D/ellipse +tags: + - API + - Canvas + - CanvasRenderingContext2D +translation_of: Web/API/CanvasRenderingContext2D/ellipse +--- +<div>{{APIRef}} {{SeeCompatTable}}</div> + +<p><code><strong>CanvasRenderingContext2D</strong></code><strong><code>.ellipse()</code></strong> 是 Canvas 2D API 添加椭圆路径的方法。椭圆的圆心在(x,y)位置,半径分别是<em>radiusX</em> 和 <em>radiusY</em> ,按照<em>anticlockwise</em>(默认顺时针)指定的方向,从 <em>startAngle </em> 开始绘制,到 <em>endAngle</em> 结束。</p> + +<h2 id="语法">语法</h2> + +<pre class="syntaxbox notranslate">void <var><em>ctx</em>.ellipse(x, y, radiusX, radiusY, rotation, startAngle, endAngle, anticlockwise);</var> +</pre> + +<h3 id="参数">参数</h3> + +<dl> + <dt><code>x</code></dt> + <dd>椭圆圆心的 x 轴坐标。</dd> + <dt><code>y</code></dt> + <dd>椭圆圆心的 y 轴坐标。</dd> + <dt><code>radius</code>X</dt> + <dd>椭圆长轴的半径。</dd> + <dt><code>radius</code>Y</dt> + <dd>椭圆短轴的半径。</dd> + <dt><code>rotation</code></dt> + <dd>椭圆的旋转角度,以弧度表示(<strong>非角度度数</strong>)。</dd> + <dt><code>startAngle</code></dt> + <dd>将要绘制的起始点角度,从 x 轴测量,以弧度表示(<strong>非角度度数</strong>)。</dd> + <dt><code>endAngle</code></dt> + <dd>椭圆将要绘制的结束点角度,以弧度表示(<strong>非角度度数</strong>)。</dd> + <dt><code>anticlockwise</code> {{optional_inline}}</dt> + <dd>{{jsxref("Boolean")}} 选项,如果为 <code>true</code>,逆时针方向绘制椭圆 (逆时针), 反之顺时针方向绘制。</dd> +</dl> + +<h2 id="示例">示例</h2> + +<h3 id="Using_the_ellipse_method" name="Using_the_ellipse_method">使用 <code>ellipse</code> 方法</h3> + +<p>这是一段绘制椭圆的简单的代码片段。</p> + +<h4 id="HTML">HTML</h4> + +<pre class="brush: html notranslate"><canvas id="canvas"></canvas> +</pre> + +<h4 id="JavaScript">JavaScript</h4> + +<pre class="notranslate"><code>var canvas = document.getElementById('canvas'); +var ctx = canvas.getContext('2d'); +ctx.setLineDash([]); +ctx.beginPath(); +ctx.ellipse(100, 100, 50, 75, 45 * Math.PI/180, 0, 2 * Math.PI); //倾斜45°角 +ctx.stroke(); +ctx.setLineDash([5]); +ctx.moveTo(0,200); +ctx.lineTo(200,0); +ctx.stroke();</code></pre> + +<p>修改下面的代码并在线查看 canvas 的变化(如果椭圆没有绘制,请在兼容性列表中检查你的浏览器是否支持):</p> + +<div style="display: none;"> +<h6 id="Playable_code" name="Playable_code">Playable code</h6> + +<pre class="brush: html notranslate"><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.setLineDash([]); +ctx.beginPath(); +ctx.ellipse(100, 100, 50, 75, 45 * Math.PI/180, 0, 2 * Math.PI); //倾斜45°角 +ctx.stroke(); +ctx.setLineDash([5]); +ctx.moveTo(0,200); +ctx.lineTo(200,0); +ctx.stroke();</textarea> +</pre> + +<pre class="brush: js notranslate">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, 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-ellipse", "CanvasRenderingContext2D.ellipse")}}</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.ellipse")}}</p> + +<h2 id="参见">参见</h2> + +<ul> + <li>接口定义, {{domxref("CanvasRenderingContext2D")}}</li> +</ul> |
