使用 Python–OpenCV
旋转图像而不切边
原文:https://www . geesforgeks . org/rotate-image-不带切边-sides-use-python-opencv/
先决条件:Python 中的图像处理(缩放、旋转、移位和边缘检测)
使用 OpenCV 旋转图像很容易，但有时简单的旋转任务会裁剪/剪切图像的侧面，从而产生半幅图像。现在，在本教程中，我们将探索一种安全旋转图像而不裁剪/剪切图像侧面的解决方案，以便整个图像都包括在旋转中，并且还将传统旋转方法与修改后的旋转版本进行比较。
循序渐进法:
- 为了在不切边的情况下旋转图像，我们将创建一个名为modified way()的显式函数，该函数将图像本身和图像旋转的角度作为参数。
- 在函数中，首先，获取图像的高度和宽度。
- 找到图像的中心。
- 然后计算 2D 旋转矩阵
- 从旋转矩阵中提取绝对 sin 和 cos 值。
- 获取图像的新高度和宽度，并更新旋转矩阵的值，以确保没有裁剪。
- 最后，使用wrappeafy()方法执行图像的实际旋转。
以下是实施办法:
Python 3
def ModifiedWay(rotateImage, angle):
# Taking image height and width
imgHeight, imgWidth = rotateImage.shape[0], rotateImage.shape[1]
# Computing the centre x,y coordinates
# of an image
centreY, centreX = imgHeight//2, imgWidth//2
# Computing 2D rotation Matrix to rotate an image
rotationMatrix = cv2.getRotationMatrix2D((centreY, centreX), angle, 1.0)
# Now will take out sin and cos values from rotationMatrix
# Also used numpy absolute function to make positive value
cosofRotationMatrix = np.abs(rotationMatrix[0][0])
sinofRotationMatrix = np.abs(rotationMatrix[0][1])
# Now will compute new height & width of
# an image so that we can use it in
# warpAffine function to prevent cropping of image sides
newImageHeight = int((imgHeight * sinofRotationMatrix) +
(imgWidth * cosofRotationMatrix))
newImageWidth = int((imgHeight * cosofRotationMatrix) +
(imgWidth * sinofRotationMatrix))
# After computing the new height & width of an image
# we also need to update the values of rotation matrix
rotationMatrix[0][2] += (newImageWidth/2) - centreX
rotationMatrix[1][2] += (newImageHeight/2) - centreY
# Now, we will perform actual image rotation
rotatingimage = cv2.warpAffine(
rotateImage, rotationMatrix, (newImageWidth, newImageHeight))
return rotatingimage
以下是一些示例，描述了如何使用上述功能旋转图像而不切边:
例 1:
下面是修改后的旋转版本的实现及其与正常旋转版本的比较:
Python 3
# Importing Required Libraries
import cv2
import numpy as np
# The below function is for conventionally way of rotating
# an Image without preventing cutting off sides
def SimpleWay(rotateImage, angle):
# Taking image height and width
imgHeight, imgWidth = rotateImage.shape[0], rotateImage.shape[1]
# Computing the centre x,y coordinates
# of an image
centreY, centreX = imgHeight//2, imgWidth//2
# Computing 2D rotation Matrix to rotate an image
rotationMatrix = cv2.getRotationMatrix2D((centreY, centreX), angle, 1.0)
# Now, we will perform actual image rotation
rotatingimage = cv2.warpAffine(
rotateImage, rotationMatrix, (imgWidth, imgHeight))
return rotatingimage
# The Below function is a modified version of the
# conventional way to rotate an image without
# cropping/cutting sides.
def ModifiedWay(rotateImage, angle):
# Taking image height and width
imgHeight, imgWidth = rotateImage.shape[0], rotateImage.shape[1]
# Computing the centre x,y coordinates
# of an image
centreY, centreX = imgHeight//2, imgWidth//2
# Computing 2D rotation Matrix to rotate an image
rotationMatrix = cv2.getRotationMatrix2D((centreY, centreX), angle, 1.0)
# Now will take out sin and cos values from rotationMatrix
# Also used numpy absolute function to make positive value
cosofRotationMatrix = np.abs(rotationMatrix[0][0])
sinofRotationMatrix = np.abs(rotationMatrix[0][1])
# Now will compute new height & width of
# an image so that we can use it in
# warpAffine function to prevent cropping of image sides
newImageHeight = int((imgHeight * sinofRotationMatrix) +
(imgWidth * cosofRotationMatrix))
newImageWidth = int((imgHeight * cosofRotationMatrix) +
(imgWidth * sinofRotationMatrix))
# After computing the new height & width of an image
# we also need to update the values of rotation matrix
rotationMatrix[0][2] += (newImageWidth/2) - centreX
rotationMatrix[1][2] += (newImageHeight/2) - centreY
# Now, we will perform actual image rotation
rotatingimage = cv2.warpAffine(
rotateImage, rotationMatrix, (newImageWidth, newImageHeight))
return rotatingimage
# Driver Code
# Loading an Image from Disk
DogImage = cv2.imread("doggy.png", 1)
# Performing 40 degree rotation
NormalRotation = SimpleWay(DogImage, 40)
ModifiedVersionRotation = ModifiedWay(DogImage, 40)
# Display image on Screen
cv2.imshow("Original Image", DogImage)
# Display rotated image on Screen
cv2.imshow("Normal Rotation", NormalRotation)
cv2.imshow("Modified Version Rotation", ModifiedVersionRotation)
# To hold the GUI screen and control until it is detected
# the input for closing it, Once it is closed
# control will be released
cv2.waitKey(0)
# To destroy and remove all created GUI windows from
#screen and memory
cv2.destroyAllWindows()
输出:
原象
使用 SimpleWay()函数的正常旋转
带 ModifiedWay()函数的旋转
例 2:
下面是另一个描述现代旋转方法的例子:
Python 3
# Importing Required Libraries
import cv2
import numpy as np
# The Below function is a modified version of the
# conventional way to rotate an image without
# cropping/cutting sides.
def ModifiedWay(rotateImage, angle):
# Taking image height and width
imgHeight, imgWidth = rotateImage.shape[0], rotateImage.shape[1]
# Computing the centre x,y coordinates
# of an image
centreY, centreX = imgHeight//2, imgWidth//2
# Computing 2D rotation Matrix to rotate an image
rotationMatrix = cv2.getRotationMatrix2D((centreY, centreX), angle, 1.0)
# Now will take out sin and cos values from rotationMatrix
# Also used numpy absolute function to make positive value
cosofRotationMatrix = np.abs(rotationMatrix[0][0])
sinofRotationMatrix = np.abs(rotationMatrix[0][1])
# Now will compute new height & width of
# an image so that we can use it in
# warpAffine function to prevent cropping of image sides
newImageHeight = int((imgHeight * sinofRotationMatrix) +
(imgWidth * cosofRotationMatrix))
newImageWidth = int((imgHeight * cosofRotationMatrix) +
(imgWidth * sinofRotationMatrix))
# After computing the new height & width of an image
# we also need to update the values of rotation matrix
rotationMatrix[0][2] += (newImageWidth/2) - centreX
rotationMatrix[1][2] += (newImageHeight/2) - centreY
# Now, we will perform actual image rotation
rotatingimage = cv2.warpAffine(
rotateImage, rotationMatrix, (newImageWidth, newImageHeight))
return rotatingimage
# Driver Code
# Loading an Image from Disk
Image = cv2.imread("gfg.png", 1)
# Performing 40 degree rotation
ModifiedVersionRotation = ModifiedWay(Image, 40)
# Display image on Screen
cv2.imshow("Original Image", Image)
# Display rotated image on Screen
cv2.imshow("Modified Version Rotation", ModifiedVersionRotation)
# To hold the GUI screen and control until it is detected
# the input for closing it, Once it is closed
# control will be released
cv2.waitKey(0)
# To destroy and remove all created GUI windows from
#screen and memory
cv2.destroyAllWindows()
输出:
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