OpenCV图像的几何变换

一、图像缩放 1.API cv2.resize(src, dsize, fx=0,fy=0,interpolation = cv2.INTER_LINEAR)

参数：

①src ：输入图像

②dsize：绝对尺寸

③fx，fy：相对尺寸

④interpolation：插值方法

2.代码演示  import cv2 as cv import numpy as np import matplotlib.pyplot as plt img = cv.imread('Genshin.jpeg', -1) cv.imshow('image', img) [rows, cols] = img.shape[:2] res_1 = cv.resize(img, (2*cols, 2*rows), interpolation=cv.INTER_CUBIC) cv.imshow('image', res_1) cv.waitKey() res_2 = cv.resize(img, None, fx=0.5, fy=0.5) cv.imshow('image', res_1) cv.waitKey() 二、图像平移 1.API cv2.warpAffine(img, M, dsize)

参数：

①img：输入图像

②M：2×3移动矩阵，为np.float32类型

③dsize：输出图像的大小

 2.代码演示  import cv2 as cv import numpy as np import matplotlib.pyplot as plt img = cv.imread('Genshin.jpeg', -1) cv.imshow('image', img) [rows, cols] = img.shape[:2] M = np.float32([[1, 0, 100], [0, 1, 50]]) dst = cv.warpAffine(img, M, (cols, rows)) cv.imshow('image', dst) cv.waitKey()

三、图像旋转 1.API cv2.getRotationMatrix2D(center, angle, scale) cv.warpAffine()

参数：

①center：旋转中心

②angle：旋转角度

③scale：缩放比例

返回值：

M：旋转矩阵 

2.代码演示  import cv2 as cv import numpy as np import matplotlib.pyplot as plt img = cv.imread('Genshin.jpeg', -1) cv.imshow('image', img) [rows, cols] = img.shape[:2] M = cv.getRotationMatrix2D((cols/2, rows/2), 120, 1) dst = cv.warpAffine(img, M, (cols, rows)) cv.imshow('image', dst) cv.waitKey()

 四、仿射变换 1.API cv2.getAffineTransform() cv2.warpAffine() 2.代码演示 import cv2 as cv import numpy as np import matplotlib.pyplot as plt img = cv.imread('Genshin.jpeg', -1) cv.imshow('image', img) [rows, cols] = img.shape[:2] pts1 = np.float32([[50, 50], [200, 50], [50, 200]]) pts2 = np.float32([[100, 100], [200, 50], [100, 250]]) M = cv.getAffineTransform(pts1, pts2) dst = cv.warpAffine(img, M, (cols, rows)) cv.imshow('image', dst) cv.waitKey()

五、透射变换 1.API cv2.getPerspectiveTransform() cv2.warpPerspective()  2.代码演示 import cv2 as cv import numpy as np import matplotlib.pyplot as plt img = cv.imread('Genshin.jpeg', -1) cv.imshow('image', img) img = cv.resize(img, None, fx=0.5, fy=0.5) [rows, cols] = img.shape[:2] pts1 = np.float32([[56, 65], [368, 52], [28, 138], [389, 390]]) pts2 = np.float32([[100, 145], [300, 100], [80, 290], [310, 300]]) T = cv.getPerspectiveTransform(pts1, pts2) dst = cv.warpPerspective(img, T, (cols, rows)) cv.imshow('image', dst) cv.waitKey()

六、图像金字塔 1.API cv2.pyrUp(img) #对图像进行上采样 cv2.pyrDown(img) #对图像进行下采样 2.代码演示 import cv2 as cv import numpy as np import matplotlib.pyplot as plt img = cv.imread('Genshin.jpeg', -1) cv.imshow('image', img) img = cv.pyrDown(img) img = cv.pyrDown(img) img = cv.pyrDown(img) cv.imshow('image', img) cv.waitKey()