图像保真旋转

import cv2
import numpy as np
from math import *
img=cv2.imread('C:/Users/xpp/Desktop/Lena.png')
img[:,:,0]=255
def rotate(image,angle):
    height, width,channels=image.shape
    #变换后新图像的大小是原图像旋转后的轮廓外接矩形，注意这个外接矩形的长和高也是水平和竖直的
    heightNew=int(width*fabs(sin(radians(angle)))+height*fabs(cos(radians(angle))))
    widthNew=int(height*fabs(sin(radians(angle)))+width*fabs(cos(radians(angle))))
    matRotation=cv2.getRotationMatrix2D((width / 2, height / 2), angle, 1)#（2，3）
    #变换矩阵的中心点相当于平移一样 原图像的中心点与新图像的中心点的相对位置
    matRotation[0,2]+=(widthNew-width)/2
    matRotation[1,2]+=(heightNew-height)/2
    imgRotation=None
    if channels==1:
        imgRotation=cv2.warpAffine(img,matRotation,(widthNew,heightNew),borderValue=(255))
    elif channels==3:
        imgRotation=cv2.warpAffine(img,matRotation,(widthNew,heightNew),borderValue=(255,255,255))
    return imgRotation
imgNew=rotate(img,60)
cv2.imshow('result',imgNew)
cv2.waitKey(0)