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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:

蟒蛇 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:

蟒蛇 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:

蟒蛇 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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