Python+OpenCV+图片旋转并用原底色填充新四角的例子

import cv2
from math import fabs, sin, cos, radians
import numpy as np
from scipy.stats import mode


def get_img_rot_broa(img, degree=45, filled_color=-1):
 """
 Desciption:
  Get img rotated a certain degree,
 and use some color to fill 4 corners of the new img.
 """

 # 获取旋转后4角的填充色
 if filled_color == -1:
 filled_color = mode([img[0, 0], img[0, -1],
    img[-1, 0], img[-1, -1]]).mode[0]
 if np.array(filled_color).shape[0] == 2:
 if isinstance(filled_color, int):
  filled_color = (filled_color, filled_color, filled_color)
 else:
 filled_color = tuple([int(i) for i in filled_color])

 height, width = img.shape[:2]

 # 旋转后的尺寸
 height_new = int(width * fabs(sin(radians(degree))) +
   height * fabs(cos(radians(degree))))
 width_new = int(height * fabs(sin(radians(degree))) +
   width * fabs(cos(radians(degree))))

 mat_rotation = cv2.getRotationMatrix2D((width / 2, height / 2), degree, 1)

 mat_rotation[0, 2] += (width_new - width) / 2
 mat_rotation[1, 2] += (height_new - height) / 2

 # Pay attention to the type of elements of filler_color, which should be
 # the int in pure python, instead of those in numpy.
 img_rotated = cv2.warpAffine(img, mat_rotation, (width_new, height_new),
     borderValue=filled_color)
 # 填充四个角
 mask = np.zeros((height_new + 2, width_new + 2), np.uint8)
 mask[:] = 0
 seed_points = [(0, 0), (0, height_new - 1), (width_new - 1, 0),
   (width_new - 1, height_new - 1)]
 for i in seed_points:
 cv2.floodFill(img_rotated, mask, i, filled_color)

 return img_rotated