Python - 旋转图像

Question

如何在OpenCv库的帮助下在Python中旋转图像,以及通过更改图像的高度和宽度值(不使用OpenCv中的内置旋转方法).它必须实现两个嵌套的for循环.

img=cv2.imread('Images/Screenshot.png',cv2.IMREAD_GRAYSCALE)

height, width = img.shape

# for i in range(0,height):
#     for j in range(0,width):
#         img[i][j]=

# show rotated image
cv2.imshow("image",img)

感谢您抽出宝贵时间来帮助我!

Answer 1

交换索引:

您可以创建一个空图像,np.zeros()然后将当前图像中的像素读取到空图像.您可以更改读取像素的顺序以执行一些基本旋转.以下示例应该有所帮助.

测试图像:

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

向左旋转90度:

h,w,c = img.shape

empty_img = np.zeros([h,w,c], dtype=np.uint8)

for i in range(h):
    for j in range(w):
        empty_img[i,j] = img[j-1,i-1]
        empty_img = empty_img[0:h,0:w]

cv2.imwrite("tester1.png", empty_img)

向右旋转90度:

h,w,c = img.shape

empty_img = np.zeros([h,w,c], dtype=np.uint8)

for i in range(h):
    for j in range(w):
        empty_img[i,j] = img[h-j-1,w-i-1]
        empty_img = empty_img[0:h,0:w]

cv2.imwrite("tester2.png", empty_img)

旋转180度:

h,w,c = img.shape

empty_img = np.zeros([h,w,c], dtype=np.uint8)

for i in range(h):
    for j in range(w):
        empty_img[i,j] = img[h-i-1,w-j-1]
        empty_img = empty_img[0:h,0:w]

cv2.imwrite("tester3.png", empty_img)

Answer 2

它必须是OpenCv吗？因为如果不是，你可以很容易地用 PIL 做到这一点：

from PIL import Image

def rotate_img(img_path, rt_degr):
    img = Image.open(img_path)
    return img.rotate(rt_degr, expand=1)

img_rt_90 = rotate_img('Images/Screenshot.png', 90)
img_rt_90.save('img_rt_90.png')

Answer 3

如果您需要在 OpenCV 中进行简单的旋转，它是内置的：

img=cv2.imread('Images/Screenshot.png',cv2.IMREAD_GRAYSCALE)

imgrot = cv2.rotate(img,cv2.ROTATE_90_CLOCKWISE)

其他可能性是cv2.ROTATE_90_COUNTERCLOCKWISE和cv2.ROTATE_180