1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
|
---
title: CanvasRenderingContext2D.clip()
slug: Web/API/CanvasRenderingContext2D/clip
translation_of: Web/API/CanvasRenderingContext2D/clip
---
<div>{{APIRef}}</div>
<p><code><strong>CanvasRenderingContext2D</strong></code><strong><code>.clip()</code></strong> 是 Canvas 2D API 将当前创建的路径设置为当前剪切路径的方法。</p>
<h2 id="语法">语法</h2>
<pre class="syntaxbox">void <var><em>ctx</em>.clip();</var>
void <var><em>ctx</em>.clip(fillRule);</var>
void <var><em>ctx</em>.clip(path, fillRule);</var>
</pre>
<h3 id="参数">参数</h3>
<p><img alt="" class="internal" src="https://mdn.mozillademos.org/files/209/Canvas_clipping_path.png" style="float: right;"></p>
<dl>
<dt><code>fillRule</code></dt>
<dd>这个算法判断一个点是在路径内还是在路径外。<br>
允许的值：
<ul>
<li><code><strong>"nonzero</strong></code>": <a href="http://en.wikipedia.org/wiki/Nonzero-rule">非零环绕原则</a>，默认的原则。</li>
<li><code><strong>"evenodd"</strong></code>: <a href="http://en.wikipedia.org/wiki/Even%E2%80%93odd_rule">奇偶环绕原则</a>。</li>
</ul>
</dd>
<dt><code>path</code></dt>
<dd>需要剪切的 {{domxref("Path2D")}} 路径。</dd>
</dl>
<h2 id="示例">示例</h2>
<h3 id="使用_clip_方法">使用 <code>clip</code> 方法</h3>
<p>这是一段简单的代码片段，使用 <code>clip</code> 方法创建剪切区域。</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");
// Create clipping region
ctx.arc(100, 100, 75, 0, Math.PI*2, false);
ctx.clip();
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.arc(100, 100, 75, 0, Math.PI*2, false);
ctx.clip();
ctx.fillRect(0, 0, 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, 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-clip", "CanvasRenderingContext2D.clip")}}</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>
<tr>
<td>Path parameter</td>
<td>{{CompatUnknown}}</td>
<td>{{ CompatGeckoDesktop(31) }}</td>
<td>{{ CompatNo }}</td>
<td>{{CompatUnknown}}</td>
<td>{{ CompatNo }}</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>
<tr>
<td>Path parameter</td>
<td>{{CompatUnknown}}</td>
<td>{{CompatUnknown}}</td>
<td>{{ CompatGeckoMobile(31) }}</td>
<td>{{CompatUnknown}}</td>
<td>{{CompatUnknown}}</td>
<td>{{CompatUnknown}}</td>
</tr>
</tbody>
</table>
</div>
<h2 id="参见">参见</h2>
<ul>
<li>接口定义， {{domxref("CanvasRenderingContext2D")}}.</li>
</ul>
|
