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author | Peter Bengtsson <mail@peterbe.com> | 2020-12-08 14:43:23 -0500 |
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committer | Peter Bengtsson <mail@peterbe.com> | 2020-12-08 14:43:23 -0500 |
commit | 218934fa2ed1c702a6d3923d2aa2cc6b43c48684 (patch) | |
tree | a9ef8ac1e1b8fe4207b6d64d3841bfb8990b6fd0 /files/zh-tw/web/api/canvasrenderingcontext2d/clearrect | |
parent | 074785cea106179cb3305637055ab0a009ca74f2 (diff) | |
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diff --git a/files/zh-tw/web/api/canvasrenderingcontext2d/clearrect/index.html b/files/zh-tw/web/api/canvasrenderingcontext2d/clearrect/index.html new file mode 100644 index 0000000000..e5792ffade --- /dev/null +++ b/files/zh-tw/web/api/canvasrenderingcontext2d/clearrect/index.html @@ -0,0 +1,189 @@ +--- +title: CanvasRenderingContext2D.clearRect() +slug: Web/API/CanvasRenderingContext2D/clearRect +translation_of: Web/API/CanvasRenderingContext2D/clearRect +--- +<div>{{APIRef}}</div> + +<p>Canvas 2D API 的 <code><strong>CanvasRenderingContext2D</strong></code><strong><code>.clearRect()</code></strong> 方法可以設定指定矩形(經由坐標 <em>(x, y)</em> 及大小 <em>(width, height)</em>)範圍內的所有像素為透明,清除所有先前繪製的內容。</p> + +<h2 id="語法">語法</h2> + +<pre class="syntaxbox">void <var><em>ctx</em>.clearRect(x, y, width, height);</var> +</pre> + +<h3 id="參數">參數</h3> + +<dl> + <dt><code>x</code></dt> + <dd>The x axis of the coordinate for the rectangle starting point.</dd> + <dt><code>y</code></dt> + <dd>The y axis of the coordinate for the rectangle starting point.</dd> + <dt><code>width</code></dt> + <dd>The rectangle's width.</dd> + <dt><code>height</code></dt> + <dd>The rectangle's height.</dd> +</dl> + +<h2 id="Usage_notes">Usage notes</h2> + +<p>A common problem with <code>clearRect</code> is that it may appear it does not work when not <a href="/en-US/docs/Web/API/Canvas_API/Tutorial/Drawing_shapes#Drawing_paths">using paths properly</a>. Don't forget to call {{domxref("CanvasRenderingContext2D.beginPath", "beginPath()")}} before starting to draw the new frame after calling <code>clearRect</code>.</p> + +<h2 id="範例">範例</h2> + +<h3 id="Using_the_clearRect_method">Using the <code>clearRect</code> method</h3> + +<p>This is just a simple code snippet which uses the <code>clearRect</code> method.</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:[11]">var canvas = document.getElementById('canvas'); +var ctx = canvas.getContext('2d'); + +ctx.beginPath(); +ctx.moveTo(20, 20); +ctx.lineTo(200, 20); +ctx.lineTo(120, 120); +ctx.closePath(); // draws last line of the triangle +ctx.stroke(); + +ctx.clearRect(10, 10, 100, 100); + +// clear the whole canvas +// ctx.clearRect(0, 0, canvas.width, canvas.height); +</pre> + +<p>Edit the code below and see your changes update live in the canvas:</p> + +<div style="display: none;"> +<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:140px;"> +ctx.beginPath(); +ctx.moveTo(20,20); +ctx.lineTo(200,20); +ctx.lineTo(120,120); +ctx.closePath(); // draws last line of the triangle +ctx.stroke(); + +ctx.clearRect(10, 10, 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, 400) }}</p> + +<h2 id="規範">規範</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-clearrect", "CanvasRenderingContext2D.clearRect")}}</td> + <td>{{Spec2('HTML WHATWG')}}</td> + <td> </td> + </tr> + </tbody> +</table> + +<h2 id="瀏覽器相容性">瀏覽器相容性</h2> + +<p>{{CompatibilityTable}}</p> + +<div id="compat-desktop"> +<table class="compat-table"> + <tbody> + <tr> + <th>Feature</th> + <th>Chrome</th> + <th>Edge</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> + <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>Edge</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> + <td>{{CompatVersionUnknown}}</td> + </tr> + </tbody> +</table> +</div> + +<h2 id="參見">參見</h2> + +<ul> + <li>The interface defining it, {{domxref("CanvasRenderingContext2D")}}</li> + <li>{{domxref("CanvasRenderingContext2D.fillRect()")}}</li> + <li>{{domxref("CanvasRenderingContext2D.strokeRect()")}}</li> +</ul> |