图像处理: 无损地旋转图像

<pre class="brush:php;toolbar:false;">import cv2# 读取原图像img = cv2.imread("./girl.jpg")h, w = img.shape[:2]center = (w // 2, h // 2)# 逆时针-90°(即顺时针90°)旋转图片M = cv2.getRotationMatrix2D(center, -90, 1)rotated_img = cv2.warpAffine(img, M, (w, h))cv2.imwrite("./rotated_img.jpg", rotated_img)

<pre class="brush:php;toolbar:false;">import cv2import numpy as np# 读取原图像img = cv2.imread("./girl.jpg")cv2.imshow("", img)cv2.waitKey(1000)# 获取输入图像的信息，生成旋转操作所需的参数（padding: 指定零填充的宽度； canter: 指定旋转的轴心坐标）h, w = img.shape[:2]padding = (w - h) // 2center = (w // 2, w // 2)# 在原图像两边做对称的零填充，使得图片由矩形变为方形img_padded = np.zeros(shape=(w, w, 3), dtype=np.uint8)img_padded[padding:padding+h, :, :] = imgcv2.imshow("", img_padded)cv2.waitKey(1000)cv2.imwrite("./img_padded.jpg", img_padded)# 逆时针-90°(即顺时针90°)旋转填充后的方形图片M = cv2.getRotationMatrix2D(center, -90, 1)rotated_padded = cv2.warpAffine(img_padded, M, (w, w))cv2.imshow("", rotated_padded)cv2.waitKey(1000)cv2.imwrite("./rotated_padded.jpg", rotated_padded)# 从旋转后的图片中截取出我们需要的部分，作为最终的输出图像output = rotated_padded[:, padding:padding+h, :]cv2.imshow("", output)cv2.waitKey(1000)cv2.imwrite("./output.jpg", output)cv2.destroyAllWindows()