OpenCV教程-OpenCV图像旋转

图像可以以各种角度旋转（90、180、270和360度）。OpenCV计算执行仿射变换的仿射矩阵，这意味着它不保留线之间的角度或点之间的距离，尽管它保留了位于直线上的点之间距离的比例。

旋转图像的语法如下：

cv2.getRotationMatrix2D(center, angle, scale rotated = cv2.warpAfifne(img,M,(w,h))  

参数：

• center： 表示图像的中心。
• angle： 表示要顺时针旋转的图像的角度。
• rotated： 包含旋转后图像数据的数组。
• scale： 值1.0表示保持形状。根据提供的值缩放图像。

示例-1

import cv2  
# read image as greyscale  
img = cv2.imread(r'C:\Users\DEVANSH SHARMA\cat.jpeg')  
# get image height, width  
(h, w) = img.shape[:2]  
# calculate the center of the image  
center = (w / 2, h / 2)  
  
angle90 = 90  
angle180 = 180  
angle270 = 270  
  
scale = 1.0  
  
# Perform the counterclockwise rotation holding at the center  
# 90 degrees  
M = cv2.getRotationMatrix2D(center, angle90, scale)  
rotated90 = cv2.warpAffine(img, M, (h, w))  
  
# 180 degrees  
M = cv2.getRotationMatrix2D(center, angle180, scale)  
rotated180 = cv2.warpAffine(img, M, (w, h))  
  
# 270 degrees  
M = cv2.getRotationMatrix2D(center, angle270, scale)  
rotated270 = cv2.warpAffine(img, M, (h, w))  
  
cv2.imshow('Original Image', img)  
cv2.waitKey(0)  # waits until a key is pressed  
cv2.destroyAllWindows()  # destroys the window showing image  
  
cv2.imshow('Image rotated by 90 degrees', rotated90)  
cv2.waitKey(0)  # waits until a key is pressed  
cv2.destroyAllWindows()  # destroys the window showing imag  
  
cv2.imshow('Image rotated by 180 degrees', rotated180)  
cv2.waitKey(0)  # waits until a key is pressed  
cv2.destroyAllWindows()  # destroys the window showing image  
  
cv2.imshow('Image rotated by 270 degrees', rotated270)  
cv2.waitKey(0)  # waits until a key is pressed  
cv2.destroyAllWindows()  # destroys the window showing image  

输出: