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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 .quadraticCurveTo() method of the Canvas 2D API adds a quadratic Bézier curve to the current sub-path. It requires two points: the first one is a control point and the second one is the end point. The starting point is the latest point in the current path, which can be changed using moveTo() before creating the quadratic Bézier curve.

句法

void ctx.quadraticCurveTo(cpx, cpy, x, y);
					

参数

cpx

The x-axis coordinate of the control point.

cpy

The y-axis coordinate of the control point.

x

The x-axis coordinate of the end point.

y

The y-axis coordinate of the end point.

范例

How quadraticCurveTo works

This example shows how a quadratic Bézier curve is drawn.

HTML

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

JavaScript

const canvas = document.getElementById('canvas');
const ctx = canvas.getContext('2d');
// Quadratic Bézier curve
ctx.beginPath();
ctx.moveTo(50, 20);
ctx.quadraticCurveTo(230, 30, 50, 100);
ctx.stroke();
// Start and end points
ctx.fillStyle = 'blue';
ctx.beginPath();
ctx.arc(50, 20, 5, 0, 2 * Math.PI);   // Start point
ctx.arc(50, 100, 5, 0, 2 * Math.PI);  // End point
ctx.fill();
// Control point
ctx.fillStyle = 'red';
ctx.beginPath();
ctx.arc(230, 30, 5, 0, 2 * Math.PI);
ctx.fill();
					

结果

在此范例中， control point is red 和 start and end points are blue .

A simple quadratic curve

This example draws a simple quadratic Bézier curve using quadraticCurveTo() .

HTML

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

JavaScript

The curve begins at the point specified by moveTo() : (20, 110). The control point is placed at (230, 150). The curve ends at (250, 20).

const canvas = document.getElementById('canvas');
const ctx = canvas.getContext('2d');
ctx.beginPath();
ctx.moveTo(20, 110);
ctx.quadraticCurveTo(230, 150, 250, 20);
ctx.stroke();
					

结果

规范

规范	状态	注释
HTML 实时标准 The definition of 'CanvasRenderingContext2D.quadraticCurveTo' 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
quadraticCurveTo	Chrome 1	Edge 12	Firefox 1.5	IE 9	Opera 11.6	Safari 3	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 12	Safari iOS 1	Samsung Internet Android 1.0

图例

完整支持

完整支持

另请参阅

• The interface defining this method: CanvasRenderingContext2D
• Wikipedia article on Bézier curves

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()