Path2D() 构造函数返回一个新的 Path2D 对象的实例，可以选择另一条路径作为参数（创建一个拷贝），或者选择 SVG path 数据构成的字符串。
语法
new Path2D();
new Path2D(path);
new Path2D(d);参数
path 可选
当调用另一个 Path2D 对象时，会创建一个 path 变量的拷贝。
d 可选
当调用 SVG path 数据构成的字符串时，会根据描述创建一个新的路径。
示例
创建和拷贝路径
这是一段简单的代码片段，创建和拷贝 Path2D 路径。
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var path1 = new Path2D();
path1.rect(10, 10, 100,100);
var path2 = new Path2D(path1);
path2.moveTo(220, 60);
path2.arc(170, 60, 50, 0, 2 * Math.PI);
ctx.stroke(path2);
修改下面的代码并在线查看 canvas 的变化：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Path2D() | Web176教程www.web176.com</title>
<meta name="robots" content="noindex, nofollow">
<style>
body {
padding: 0;
margin: 0;
}
svg:not(:root) {
display: block;
}
.playable-code {
background-color: #f4f7f8;
border: none;
border-left: 6px solid #558abb;
border-width: medium medium medium 6px;
color: #4d4e53;
height: 100px;
width: 90%%;
padding: 10px 10px 0;
}
.playable-canvas {
border: 1px solid #4d4e53;
border-radius: 2px;
}
.playable-buttons {
text-align: right;
width: 90%%;
padding: 5px 10px 5px 26px;
}
</style>
</head>
<body>
<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: 150px">
var path1 = new Path2D();
path1.rect(10, 10, 100,100);
var path2 = new Path2D(path1);
path2.moveTo(220, 60);
path2.arc(170, 60, 50, 0, 2 * Math.PI);
ctx.stroke(path2);</textarea>
<script>
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var path1 = new Path2D();
path1.rect(10, 10, 100,100);
var path2 = new Path2D(path1);
path2.moveTo(220, 60);
path2.arc(170, 60, 50, 0, 2 * Math.PI);
ctx.stroke(path2);
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);
</script>
</body>
</html>
使用 SVG 路径
这是一段简单的代码片段，使用 SVG path data 创建一个 Path2D 路径。路径将会移动到点 (M10 10) ，然后向右侧水平移动 80 个点 (h 80)，然后向下 80 个点 (v 80)，然后向左 80 个点 (h -80)，最后回到起始点 (z)。
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var p = new Path2D("M10 10 h 80 v 80 h -80 Z");
ctx.fill(p);
修改下面的代码并在线查看 canvas 的变化：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Path2D() - playable_code2 | Web176教程www.web176.com</title>
<meta name="robots" content="noindex, nofollow">
<style>
body {
padding: 0;
margin: 0;
}
svg:not(:root) {
display: block;
}
.playable-code {
background-color: #f4f7f8;
border: none;
border-left: 6px solid #558abb;
border-width: medium medium medium 6px;
color: #4d4e53;
height: 100px;
width: 90%%;
padding: 10px 10px 0;
}
.playable-canvas {
border: 1px solid #4d4e53;
border-radius: 2px;
}
.playable-buttons {
text-align: right;
width: 90%%;
padding: 5px 10px 5px 26px;
}
</style>
</head>
<body>
<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">
var p = new Path2D("M10 10 h 80 v 80 h -80 Z");
ctx.fill(p);</textarea>
<script>
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var p = new Path2D("M10 10 h 80 v 80 h -80 Z");
ctx.fill(p);
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);
</script>
</body>
</html>
作者：terry，如若转载，请注明出处：https://www.web176.com/canvas_api/7734.html
