在此页

• 句法
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

CanvasRenderingContext2D .lineDashOffset property of the Canvas 2D API sets the line dash offset, or "phase."

注意： Lines are drawn by calling the stroke() 方法。

句法

ctx.lineDashOffset = value;
					

value

A float specifying the amount of the line dash offset. The default value is 0.0 .

范例

Offsetting a line dash

This example draws two dashed lines. The first has no dash offset. The second has a dash offset of 4.

HTML

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

JavaScript

const canvas = document.getElementById('canvas');
const ctx = canvas.getContext('2d');
ctx.setLineDash([4, 16]);
// Dashed line with no offset
ctx.beginPath();
ctx.moveTo(0, 50);
ctx.lineTo(300, 50);
ctx.stroke();
// Dashed line with offset of 4
ctx.beginPath();
ctx.strokeStyle = 'red';
ctx.lineDashOffset = 4;
ctx.moveTo(0, 100);
ctx.lineTo(300, 100);
ctx.stroke();
					

结果

The line with a dash offset is drawn in red.

Marching ants

marching ants effect is an animation technique often found in selection tools of computer graphics programs. It helps the user to distinguish the selection border from the image background by animating the border.

HTML

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

const canvas = document.getElementById('canvas');
const ctx = canvas.getContext('2d');
let offset = 0;
function draw() {
  ctx.clearRect(0, 0, canvas.width, canvas.height);
  ctx.setLineDash([4, 2]);
  ctx.lineDashOffset = -offset;
  ctx.strokeRect(10, 10, 100, 100);
}
function march() {
  offset++;
  if (offset > 16) {
    offset = 0;
  }
  draw();
  setTimeout(march, 20);
}
march();
					

规范

规范	状态	注释
HTML 实时标准 The definition of 'CanvasRenderingContext2D.lineDashOffset' 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
lineDashOffset	Chrome Yes	Edge 12	Firefox 27 27 7 Alternate Name Alternate Name Uses the non-standard name: mozDashOffset	IE 11	Opera Yes	Safari Yes	WebView Android Yes	Chrome Android Yes	Firefox Android 27 27 7 Alternate Name Alternate Name Uses the non-standard name: mozDashOffset	Opera Android Yes	Safari iOS Yes	Samsung Internet Android Yes

图例

完整支持

完整支持

使用非标名称。

另请参阅

• The interface defining this property: CanvasRenderingContext2D
• CanvasRenderingContext2D.getLineDash()
• CanvasRenderingContext2D.setLineDash()
• Applying styles and color

元数据

• 最后修改： Apr 3, 2020

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()