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.bezierCurveTo()
slug: Web/API/CanvasRenderingContext2D/bezierCurveTo
tags:
- API
- Canvas
- CanvasRenderingContext2D
- Method
- Reference
translation_of: Web/API/CanvasRenderingContext2D/bezierCurveTo
---
<div>{{APIRef}}</div>
<p><code><strong>CanvasRenderingContext2D</strong></code><strong><code>.bezierCurveTo()</code></strong> 是 Canvas 2D API 绘制三次贝赛尔曲线路径的方法。 该方法需要三个点。 第一、第二个点是控制点，第三个点是结束点。起始点是当前路径的最后一个点，绘制贝赛尔曲线前，可以通过调用 <code>moveTo()</code> 进行修改。</p>
<h2 id="语法">语法</h2>
<pre class="syntaxbox">void <var><em>ctx</em>.bezierCurveTo(cp1x, cp1y, cp2x, cp2y, x, y);</var>
</pre>
<h3 id="参数">参数</h3>
<dl>
<dt><code>cp1x</code></dt>
<dd>第一个控制点的 x 轴坐标。</dd>
<dt><code>cp1y</code></dt>
<dd>第一个控制点的 y 轴坐标。</dd>
<dt><code>cp2x</code></dt>
<dd>第二个控制点的 x 轴坐标。</dd>
<dt><code>cp2y</code></dt>
<dd>第二个控制点的 y 轴坐标。</dd>
<dt><code>x</code></dt>
<dd>结束点的 x 轴坐标。</dd>
<dt><code>y</code></dt>
<dd>结束点的 y 轴坐标。</dd>
</dl>
<h2 id="示例">示例</h2>
<h3 id="使用_bezierCurveTo_方法">使用 <code>bezierCurveTo</code> 方法</h3>
<p>这是一段绘制贝赛尔曲线的简单的代码片段。 <span style="color: red;">控制点是红色的</span>，<span style="color: blue;"> 开始和结束点是蓝色的。</span></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.beginPath();
ctx.moveTo(50,20);
ctx.bezierCurveTo(230, 30, 150, 60, 50, 100);
ctx.stroke();
ctx.fillStyle = 'blue';
// start point
ctx.fillRect(50, 20, 10, 10);
// end point
ctx.fillRect(50, 100, 10, 10);
ctx.fillStyle = 'red';
// control point one
ctx.fillRect(230, 30, 10, 10);
// control point two
ctx.fillRect(150, 70, 10, 10);</pre>
<p>{{ EmbedLiveSample('使用_bezierCurveTo_方法', 315, 165) }}</p>
<h3 id="尝试_bezierCurveTo_参数">尝试 <code>bezierCurveTo</code> 参数</h3>
<p>修改下面的代码并在线查看 canvas 的变化：</p>
<div class="hidden">
<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.beginPath();
ctx.bezierCurveTo(50, 100, 180, 10, 20, 10);
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('尝试_bezierCurveTo_参数', 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-beziercurveto", "CanvasRenderingContext2D.beziercurveto")}}</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>
<li><a href="http://en.wikipedia.org/wiki/B%C3%A9zier_curve">维基百科关于贝赛尔曲线</a>。</li>
</ul>
|
