diff options
Diffstat (limited to 'files/zh-cn/web/api/canvasrenderingcontext2d/arcto/index.html')
| -rw-r--r-- | files/zh-cn/web/api/canvasrenderingcontext2d/arcto/index.html | 212 |
1 files changed, 212 insertions, 0 deletions
diff --git a/files/zh-cn/web/api/canvasrenderingcontext2d/arcto/index.html b/files/zh-cn/web/api/canvasrenderingcontext2d/arcto/index.html new file mode 100644 index 0000000000..8c8e2dc5ff --- /dev/null +++ b/files/zh-cn/web/api/canvasrenderingcontext2d/arcto/index.html @@ -0,0 +1,212 @@ +--- +title: CanvasRenderingContext2D.arcTo() +slug: Web/API/CanvasRenderingContext2D/arcTo +translation_of: Web/API/CanvasRenderingContext2D/arcTo +--- +<div>{{APIRef}}</div> + +<p><code><strong>CanvasRenderingContext2D</strong></code><strong><code>.arcTo()</code></strong> 是 Canvas 2D API 根据控制点和半径绘制圆弧路径，使用当前的描点(前一个moveTo或lineTo等函数的止点)。根据当前描点与给定的控制点1连接的直线，和控制点1与控制点2连接的直线，作为使用指定半径的圆的<strong>切线</strong>，画出两条切线之间的弧线路径。</p> + +<h2 id="语法">语法</h2> + +<pre class="syntaxbox">void <var><em>ctx</em>.arcTo(x1, y1, x2, y2, radius);</var> +</pre> + +<h3 id="Parameters">Parameters</h3> + +<dl> + <dt><code>x1</code></dt> + <dd>第一个控制点的 x 轴坐标。</dd> + <dt><code>y1</code></dt> + <dd>第一个控制点的 y 轴坐标。</dd> + <dt><code>x2</code></dt> + <dd>第二个控制点的 x 轴坐标。</dd> + <dt><code>y2</code></dt> + <dd>第二个控制点的 y 轴坐标。</dd> + <dt><code>radius</code></dt> + <dd>圆弧的半径。</dd> +</dl> + +<h2 id="示例">示例</h2> + +<h3 id="Using_the_arc_method" name="Using_the_arc_method">使用 <code>arcTo</code> 方法</h3> + +<p>这是一段绘制圆弧的简单的代码片段。 基础点是蓝色的，两个控制点是红色的。</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:[6]">var canvas = document.getElementById("canvas"); +var ctx = canvas.getContext("2d"); + +ctx.setLineDash([]) +ctx.beginPath(); +ctx.moveTo(150, 20); +ctx.arcTo(150,100,50,20,30); +ctx.stroke(); + +ctx.fillStyle = 'blue'; +// base point +ctx.fillRect(150, 20, 10, 10); + +ctx.fillStyle = 'red'; +// control point one +ctx.fillRect(150, 100, 10, 10); +// control point two +ctx.fillRect(50, 20, 10, 10); +// +ctx.setLineDash([5,5]) +ctx.moveTo(150, 20); +ctx.lineTo(150,100); +ctx.lineTo(50, 20); +ctx.stroke(); +ctx.beginPath(); +ctx.arc(120,38,30,0,2*Math.PI); +ctx.stroke(); +</pre> + +<p>{{ EmbedLiveSample('Using_the_arc_method', 315, 165) }}</p> + +<h3 id="Trying_the_arcTo_parameters" name="Trying_the_arcTo_parameters">尝试 <code>arcTo</code> 参数</h3> + +<p>修改下面的代码并在线查看 canvas 的变化：</p> + +<div style="display: none;"> +<pre class="brush: html"><canvas id="canvas" class="playable-canvas" height="200" width="400"></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.moveTo(150, 20); +ctx.arcTo(150,100,50,20,30); +ctx.stroke(); + +ctx.fillStyle = 'blue'; +// base point +ctx.fillRect(150, 20, 10, 10); + +ctx.fillStyle = 'red'; +// control point one +ctx.fillRect(150, 100, 10, 10); +// control point two +ctx.fillRect(50, 20, 10, 10); +// +ctx.setLineDash([5,5]) +ctx.moveTo(150, 20); +ctx.lineTo(150,100); +ctx.lineTo(50, 20); +ctx.stroke(); +ctx.beginPath(); +ctx.arc(120,38,30,0,2*Math.PI); +ctx.stroke();</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('Trying_the_arcTo_parameters', 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-arcto", "CanvasRenderingContext2D.arcTo")}}</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> +</ul> |