python opencv–getremotion matrix 2d()函数

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cv2 . getrotationmatrix2d()函数用于生成变换矩阵 M，该矩阵将用于旋转图像。

语法:

cv2.getRotationMatrix2D(中心、角度、比例)

参数:

  • 中心:旋转中心
  • 角度(θ): 旋转角度。逆时针方向的角度为正，顺时针方向的角度为负。
  • 比例:缩放图像的比例因子

返回: 2×3 旋转矩阵 M

M = \begin{bmatrix} \alpha & \beta & (1-\alpha)\cdot c_x-\beta \cdot c_y\ -\beta & \alpha & \beta\cdot c_x+(1-\alpha) \cdot c_y \end{bmatrix}

哪里，

\alpha = scale\cdot cos(\theta)\ \beta = scale\cdot sin(\theta)\ c_x\ and\ c_y\ are\ the\ coordinates\ of\ the\ center\ of\ the\ image.\

这是一种仿射变换。仿射变换是保持直线和平行度的变换。warpaffine()函数将这些变换矩阵作为参数，并返回旋转后的图像。

使用的图像:

例 1:

Python 3

import cv2

# Reading the image
image = cv2.imread('image.jpeg')

# Extracting height and width from 
# image shape
height, width = image.shape[:2]

# get the center coordinates of the
# image to create the 2D rotation
# matrix
center = (width/2, height/2)

# using cv2.getRotationMatrix2D() 
# to get the rotation matrix
rotate_matrix = cv2.getRotationMatrix2D(center=center, angle=90, scale=1)

# rotate the image using cv2.warpAffine 
# 90 degree anticlockwise
rotated_image = cv2.warpAffine(
    src=image, M=rotate_matrix, dsize=(width, height))

cv2.imshow("rotated image:", rotated_image)
cv2.imwrite('rotated_image.jpg', rotated_image)

输出-

例 2:

Python 3

import cv2

# Reading the image
image = cv2.imread('image.jpeg')

# Extracting height and width from 
# image shape
height, width = image.shape[:2]

# get the center coordinates of the 
# image to create the 2D rotation matrix
center = (width/2, height/2)

# using cv2.getRotationMatrix2D() to get
# the rotation matrix
rotate_matrix = cv2.getRotationMatrix2D(center=center, angle=-90, scale=1)

# rotate the image using cv2.warpAffine 90 
# degree clockwise
rotated_image = cv2.warpAffine(
    src=image, M=rotate_matrix, dsize=(width, height))

cv2.imshow("rotated image:",rotated_image)
cv2.imwrite('rotated_image.jpg', rotated_image)

输出-

Python 3

import cv2

# Reading the image
image = cv2.imread('image.jpeg')

# Extracting height and width from image shape
height, width = image.shape[:2]

# get the center coordinates of the image to 
# create the 2D rotation matrix
center = (width/2, height/2)

# using cv2.getRotationMatrix2D() to get 
# the rotation matrix
rotate_matrix = cv2.getRotationMatrix2D(center=center, angle=180, scale=1)

# rotate the image using cv2.warpAffine 180 
# degree anticlockwise
rotated_image = cv2.warpAffine(
    src=image, M=rotate_matrix, dsize=(width, height))

cv2.imshow("rotated image:", rotated_image)
cv2.imwrite('rotated_image.jpg', rotated_image)

输出-

例 4:

Python 3

import cv2

# Reading the image
image = cv2.imread('image.jpeg')

# Extracting height and width from image shape
height, width = image.shape[:2]

# get the center coordinates of the image to
# create the 2D rotation matrix
center = (width/2, height/2)

# using cv2.getRotationMatrix2D() to get the
# rotation matrix
rotate_matrix = cv2.getRotationMatrix2D(center=center, angle=-180, scale=1)

# rotate the image using cv2.warpAffine 180
# degree clockwise
rotated_image = cv2.warpAffine(
    src=image, M=rotate_matrix, dsize=(width, height))

cv2.imshow("rotated image:", rotated_image)
cv2.imwrite('rotated_image.jpg', rotated_image)

输出–

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