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• 句法
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

CanvasRenderingContext2D .lineJoin property of the Canvas 2D API determines the shape used to join two line segments where they meet.

This property has no effect wherever two connected segments have the same direction, because no joining area will be added in this case. Degenerate segments with a length of zero (i.e., with all endpoints and control points at the exact same position) are also ignored.

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

句法

ctx.lineJoin = "bevel" || "round" || "miter";
					

选项

There are three possible values for this property: "round" , "bevel" ，和 "miter" 。默认为 "miter" .

"round"

Rounds off the corners of a shape by filling an additional sector of disc centered at the common endpoint of connected segments. The radius for these rounded corners is equal to the line width.

"bevel"

Fills an additional triangular area between the common endpoint of connected segments, and the separate outside rectangular corners of each segment.

"miter"

Connected segments are joined by extending their outside edges to connect at a single point, with the effect of filling an additional lozenge-shaped area. This setting is affected by the miterLimit property. Default value.

范例

Changing the joins in a path

This example applies rounded line joins to a path.

HTML

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

JavaScript

const canvas = document.getElementById('canvas');
const ctx = canvas.getContext('2d');
ctx.lineWidth = 20;
ctx.lineJoin = 'round';
ctx.beginPath();
ctx.moveTo(20, 20);
ctx.lineTo(190, 100);
ctx.lineTo(280, 20);
ctx.lineTo(280, 150);
ctx.stroke();
					

结果

Comparison of line joins

The example below draws three different paths, demonstrating each of the three lineJoin 选项。

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

var ctx = document.getElementById('canvas').getContext('2d');
var lineJoin = ['round', 'bevel', 'miter'];
ctx.lineWidth = 10;
for (let i = 0; i < lineJoin.length; i++) {
  ctx.lineJoin = lineJoin[i];
  ctx.beginPath();
  ctx.moveTo(-5, 5 + i * 40);
  ctx.lineTo(35, 45 + i * 40);
  ctx.lineTo(75, 5 + i * 40);
  ctx.lineTo(115, 45 + i * 40);
  ctx.lineTo(155, 5 + i * 40);
  ctx.stroke();
}
					

Screenshot	Live sample

规范

规范	状态	注释
HTML 实时标准 The definition of 'CanvasRenderingContext2D.lineJoin' 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
lineJoin	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

完整支持

WebKit/Blink-specific notes

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

另请参阅

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

元数据

• 最后修改： 2019 年 3 月 23 日

相关话题

1. CanvasRenderingContext2D
2. 特性

   1. canvas
   2. currentTransform
   3. direction
   4. fillStyle
   5. filter
   6. font
   7. globalAlpha
   8. globalCompositeOperation
   9. imageSmoothingEnabled
   10. imageSmoothingQuality
   11. lineCap
   12. lineDashOffset
   13. lineJoin
   14. lineWidth
   15. miterLimit
   16. shadowBlur
   17. shadowColor
   18. shadowOffsetX
   19. shadowOffsetY
   20. strokeStyle
   21. textAlign
   22. textBaseline
3. 方法

   1. addHitRegion()
   2. arc()
   3. arcTo()
   4. beginPath()
   5. bezierCurveTo()
   6. clearHitRegions()
   7. clearRect()
   8. clip()
   9. closePath()
   10. createImageData()
   11. createLinearGradient()
   12. createPattern()
   13. createRadialGradient()
   14. drawFocusIfNeeded()
   15. drawImage()
   16. drawWidgetAsOnScreen()
   17. drawWindow()
   18. ellipse()
   19. fill()
   20. fillRect()
   21. fillText()
   22. getImageData()
   23. getLineDash()
   24. getTransform()
   25. isPointInPath()
   26. isPointInStroke()
   27. lineTo()
   28. measureText()
   29. moveTo()
   30. putImageData()
   31. quadraticCurveTo()
   32. rect()
   33. removeHitRegion()
   34. resetTransform()
   35. restore()
   36. rotate()
   37. save()
   38. scale()
   39. scrollPathIntoView()
   40. setLineDash()
   41. setTransform()
   42. stroke()
   43. strokeRect()
   44. strokeText()
   45. transform()
   46. translate()