在此页

• 句法
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

CanvasRenderingContext2D .rotate() method of the Canvas 2D API adds a rotation to the transformation matrix.

句法

void ctx.rotate(angle);
					

参数

angle

The rotation angle, clockwise in radians. You can use degree * Math.PI / 180 to calculate a radian from a degree.

The rotation center point is always the canvas origin. To change the center point, you will need to move the canvas by using the translate() 方法。

范例

Rotating a shape

This example rotates a rectangle by 45°. Note that the center of rotation is the top-left corner of the canvas, and not a location relative to any shape.

HTML

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

JavaScript

const canvas = document.getElementById('canvas');
const ctx = canvas.getContext('2d');
// Point of transform origin
ctx.arc(0, 0, 5, 0, 2 * Math.PI);
ctx.fillStyle = 'blue';
ctx.fill();
// Non-rotated rectangle
ctx.fillStyle = 'gray';
ctx.fillRect(100, 0, 80, 20);
// Rotated rectangle
ctx.rotate(45 * Math.PI / 180);
ctx.fillStyle = 'red';
ctx.fillRect(100, 0, 80, 20);
// Reset transformation matrix to the identity matrix
ctx.setTransform(1, 0, 0, 1, 0, 0);
					

结果

center of rotation is blue 。 non-rotated rectangle is gray ，和 rotated rectangle is red .

Rotating a shape around its center

This example rotates a shape around its center point. To do this, the following steps are applied to the matrix:

1. 首先， translate() moves the matrix's origin to the shape's center.
2. rotate() rotates the matrix by the desired amount.
3. 最后， translate() moves the matrix's origin back to its starting point. This is done by applying the values of the shape's center coordinates in a negative direction.

HTML

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

JavaScript

The shape is a rectangle with its corner at (80, 60), a width of 140, a height of 30. Its horizontal center is at (80 + 140 / 2), or 150. Its vertical center is at (60 + 30 / 2), or 75. Thus, the center point is at (150, 75).

const canvas = document.getElementById('canvas');
const ctx = canvas.getContext('2d');
// Non-rotated rectangle
ctx.fillStyle = 'gray';
ctx.fillRect(80, 60, 140, 30);
// Matrix transformation
ctx.translate(150, 75);
ctx.rotate(Math.PI / 2);
ctx.translate(-150, -75);
// Rotated rectangle
ctx.fillStyle = 'red';
ctx.fillRect(80, 60, 140, 30);
					

结果

non-rotated rectangle is gray ，和 rotated rectangle is red .

规范

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

另请参阅

• The interface defining this method: CanvasRenderingContext2D

元数据

• 最后修改： Oct 20, 2019

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()