opencv, cv2, rotate image & point

 

refer to code.

sample point is 100,100

firstly, I rotated image as 90 degree and point.

And compare origin image & pt where rotated point is placed in right position.

..

import numpy as np

import cv2

from matplotlib import pyplot as plt

def rotate_image(angle, width, height):

image_center = (width/2, height/2)

rotation_mat = cv2.getRotationMatrix2D(image_center, angle, 1.)

abs_cos = abs(rotation_mat[0,0])

abs_sin = abs(rotation_mat[0,1])

bound_w = int(height * abs_sin + width * abs_cos)

bound_h = int(height * abs_cos + width * abs_sin)

rotation_mat[0, 2] += bound_w/2 - image_center[0]

rotation_mat[1, 2] += bound_h/2 - image_center[1]

return rotation_mat, (bound_w, bound_h)

#open image

image = cv2.imread('img.png')

sample_pt =(100,100)

#get rotate mat, bound

height, width = image.shape[:2]

rotation_mat, (bound_w, bound_h) = rotate_image(90, width, height)

#rotate image

image_90 = cv2.warpAffine(image, rotation_mat, (bound_w, bound_h))

#rotate pt

sample = np.array([100, 100, 1])

sample_90 = np.matmul(rotation_mat, sample)

#origin image & pt

cv2.circle(image, sample_pt, 1, (0, 0, 255), 2, cv2.LINE_AA)

#rotated image & pt

cv2.circle(image_90, (int(sample_90[0]), int(sample_90[1])), 1, (0, 0, 255), 2, cv2.LINE_AA)

image = image[:,:,::-1]

plt.figure(figsize=(10, 10), dpi=100)

plt.imshow(image)

image_90 = image_90[:,:,::-1]

plt.figure(figsize=(10, 10), dpi=100)

plt.imshow(image_90)

..

origin image with point

90 rotated image and point

Thank you.

www.marearts.com