OpenCV Python：旋转图像而不裁剪边

Question

想象一下，我有这些图片：

我希望左边的图像像中间的图像一样旋转，而不是正确的图像。我如何使用Python和OpenCV来做到这一点。我查看了getRotationMatrix2D和warpAffine，但有关它的示例会将我的图像转换为正确的图像。

Answer 1

这是迄今为止我发现的旋转图像同时避免裁剪图像的最佳解决方案。

Rotate an image without cropping in OpenCV in C++

one.innerHTML += "Today is : " + days[d.getDay()] + "\n";
one.innerHTML += " Current time is : " + d.getHours() + " : " + d.getMinutes() + " : " + d.getSeconds();

当角度为90 * n时，您可以添加检查以避免某些计算，但此功能将适用于任何角度。

Answer 2

由于我不知道您的代码，我仍然会猜测使用imutils.rotate_bound函数可以解决问题。例如：rotate = imutils.rotate_bound(image, angle)

Answer 3

如果您仅关心numpy的90度旋转。这要容易得多，并且可以在opencv输入上使用：

import numpy as np
rotated_image = np.rot90(im)

Answer 4

您也可以使用填充，即在图像的两侧添加边框，然后旋转它以避免从原始图像中裁剪。

def rotate_im(image, angle)
    image_height = image.shape[0]
    image_width = image.shape[1]
    diagonal_square = (image_width*image_width) + (
        image_height* image_height
    )
    #
    diagonal = round(sqrt(diagonal_square))
    padding_top = round((diagonal-image_height) / 2)
    padding_bottom = round((diagonal-image_height) / 2)
    padding_right = round((diagonal-image_width) / 2)
    padding_left = round((diagonal-image_width) / 2)
    padded_image = cv2.copyMakeBorder(image,
                                      top=padding_top,
                                      bottom=padding_bottom,
                                      left=padding_left,
                                      right=padding_right,
                                      borderType=cv2.BORDER_CONSTANT,
                                      value=0
            )
    padded_height = padded_image.shape[0]
    padded_width = padded_image.shape[1]
    transform_matrix = cv2.getRotationMatrix2D(
                (padded_height/2,
                 padded_width/2), # center
                angle, # angle
      1.0) # scale
    rotated_image = cv2.warpAffine(padded_image,
                                   transform_matrix,
                                   (diagonal, diagonal),
                                   flags=cv2.INTER_LANCZOS4)
    return rotated_image

Answer 5

这是通过使用cv2.rotate（frame，rotateCode = 1）旋转图像帧并通过使用帧的cv2.CAP_PROP_FRAME_WIDTH和cv2.CAP_PROP_FRAME_HEIGHT来缩放或调整大小的最简单方法。

import numpy as np
import cv2

cam = cv2.VideoCapture(2)

while(True):
    # Capture frame-by-frame
    cam.set(cv2.CAP_PROP_FRAME_WIDTH, 640) # You can change frame width by chaning number.

    cam.set(cv2.CAP_PROP_FRAME_HEIGHT, 480) # You can change frame height by chaning number.

    ret, frame = cam.read()

    new_frame=cv2.rotate(frame,rotateCode = 1) 

您可以输入rotateCode = 0或1或2。取决于您的旋转方式。它会为您提供0或90或180或270个角度

    # Display the resulting frame
    cv2.imshow('frame',new_frame)

    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

# When everything done, release the capture
cam.release()
cv2.destroyAllWindows()

希望它能对您有所帮助。

Answer 6

它的简单不需要任何warpaffine或任何计算检查此代码

import numpy as np
from PIL import ImageGrab
import cv2

angle = -90
scale = 1.0

while True:
    img = ImageGrab.grab()
    img_np = np.array(img)
    frame = cv2.cvtColor(img_np, cv2.COLOR_BGR2RGB)
    new = cv2.rotate(frame,rotateCode = 0)# this is the line to rotate the image
    true = cv2.resize(new, (0,0), fx = 0.6, fy = 0.6) # with fxand fy u can control the size
    cv2.imshow('output', true)
    if cv2.waitKey(1) == 27:
        break


cv2.destroyAllWindows()