CanvasRenderingContext2D.lineCap

在此页

句法
范例
规范
浏览器兼容性
另请参阅
相关话题

CanvasRenderingContext2D .lineCap property of the Canvas 2D API determines the shape used to draw the end points of lines.

注意： Lines can be drawn with the stroke() , strokeRect() ，和 strokeText() 方法。

句法

ctx.lineCap = "butt" || "round" || "square";

选项

"butt"
"round"
"square"

范例

Changing the shape of line caps

This example rounds the end caps of a straight line.

HTML

<canvas id="canvas"></canvas>

JavaScript

const canvas = document.getElementById('canvas');
const ctx = canvas.getContext('2d');
ctx.beginPath();
ctx.moveTo(20, 20);
ctx.lineWidth = 15;
ctx.lineCap = 'round';
ctx.lineTo(100, 100);
ctx.stroke();

结果

Comparison of line caps

In this example three lines are drawn, each with a different value for the lineCap property. Two guides to see the exact differences between the three are added. Each of these lines starts and ends exactly on these guides.

The line on the left uses the default "butt" option. It's drawn completely flush with the guides. The second is set to use the "round" option. This adds a semicircle to the end that has a radius half the width of the line. The line on the right uses the "square" option. This adds a box with an equal width and half the height of the line thickness.

<canvas id="canvas" width="150" height="150"></canvas>

const canvas = document.getElementById('canvas');
const ctx = canvas.getContext('2d');
const lineCap = ['butt', 'round', 'square'];
// Draw guides
ctx.strokeStyle = '#09f';
ctx.beginPath();
ctx.moveTo(10, 10);
ctx.lineTo(140, 10);
ctx.moveTo(10, 140);
ctx.lineTo(140, 140);
ctx.stroke();
// Draw lines
ctx.strokeStyle = 'black';
for (let i = 0; i < lineCap.length; i++) {
  ctx.lineWidth = 15;
  ctx.lineCap = lineCap[i];
  ctx.beginPath();
  ctx.moveTo(25 + i * 50, 10);
  ctx.lineTo(25 + i * 50, 140);
  ctx.stroke();
}

Screenshot	Live sample

规范

规范	状态	注释
HTML 实时标准 The definition of 'CanvasRenderingContext2D.lineCap' in that specification.	实时标准

浏览器兼容性

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request. 更新 GitHub 上的兼容性数据

	桌面						移动
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`lineCap`	Chrome Yes	Edge 12	Firefox 1.5	IE Yes	Opera Yes	Safari Yes	WebView Android Yes	Chrome Android Yes	Firefox Android 4	Opera Android Yes	Safari iOS Yes	Samsung Internet Android Yes

图例

完整支持

WebKit/Blink-specific notes

In WebKit- and Blink-based Browsers, a non-standard and deprecated method ctx.setLineCap() is implemented in addition to this property.

另请参阅

The interface defining this property: CanvasRenderingContext2D
CanvasRenderingContext2D.lineWidth
CanvasRenderingContext2D.lineJoin
Applying styles and color

元数据

最后修改： 2019 年 3 月 23 日

在此页

句法

选项

范例