【opencv+python】图像的基本操作：缩放、剪切、位移、旋转、仿射变换

1.缩放

代码：

# 使用resize函数实现图片缩放
import cv2
src = cv2.imread("C:/360Downloads/1.jpg", 1)
cv2.imshow("src", src)
srcInfo = src.shape
height = srcInfo[0]
width = srcInfo[1]

dstHeight = int(height * 0.5)
dstWidth = int(width * 0.5)

dst = cv2.resize(src, (dstWidth, dstHeight))
cv2.imshow("dst", dst)
cv2.waitKey(0)


# 使用warpAffine函数实现图片缩放
import cv2
import numpy as np
src = cv2.imread("C:/360Downloads/1.jpg", 1)
cv2.imshow("src", src)
srcInfo = src.shape
height = int(srcInfo[0]/2)
width = int(srcInfo[1]/2)

# 将图片缩小为原来的一半：
# xNew = x * 0.5
# yNew = y * 0.5

# xNew = x * A1 + y * A2 + B1
# yNew = x * A3 + y * A4 + B2

# np.float32([[A1, A3, B1],
#             [A2, A4, B2]])
matScale = np.float32([[0.5, 0, 0],
                       [0, 0.5, 0]])

dst = cv2.warpAffine(src, matScale, (width, height))
cv2.imshow("dst", dst)
cv2.waitKey(0)

效果：

 

2.剪切

代码：

# 图片剪切
import cv2
src = cv2.imread("C:/360Downloads/1.jpg", 1)
cv2.imshow("src", src)

# [行，列]
dst = src[100:200, 100:300]
cv2.imshow("dst", dst)
cv2.waitKey(0)

效果：

 

 

3.位移

代码：

# 图像位移
import cv2
import numpy as np
src = cv2.imread("C:/360Downloads/1.jpg", 1)
cv2.imshow("src", src)
srcInfo = src.shape
height = srcInfo[0]
width = srcInfo[1]

# 左移100，下移200：
# xNew = x + 100
# yNew = y + 200

# xNew = x * A1 + y * A2 + B1
# yNew = x * A3 + y * A4 + B2

# np.float32([[A1, A3, B1],
#             [A2, A4, B2]])
matShift = np.float32([[1, 0, 100], [0, 1, 200]])
dst = cv2.warpAffine(src, matShift, (width, height))

cv2.imshow("dst", dst)
cv2.waitKey(0)

效果：

 

 

4.旋转

代码：

# 旋转图像
import cv2
src = cv2.imread("C:/360Downloads/1.jpg", 1)
cv2.imshow("src", src)
srcInfo = src.shape
height = srcInfo[0]
width = srcInfo[1]

# getRotationMatrix2D 函数可获取旋转的仿射矩阵
# 参数依次为（旋转中心，旋转角度，缩放比例）
matRotate = cv2.getRotationMatrix2D((0, 0), 45, 0.5)
dst = cv2.warpAffine(src, matRotate, (width, height))

cv2.imshow("dst", dst)
cv2.waitKey(0)

效果：

 

 

5.仿射变换

代码：

# 仿射变换
import cv2
import numpy as np
src = cv2.imread("C:/360Downloads/1.jpg", 1)
cv2.imshow("src", src)
srcInfo = src.shape
height = srcInfo[0]
width = srcInfo[1]

# 三点确定一个平面
# getAffineTransform 函数可获取仿射矩阵
# 参数依次为（源图像的三点坐标，目标图像的三点坐标）
# 三点分别为（左上角，左下角，右上角）
matSrc = np.float32([[0, 0], [0, height - 1], [width - 1, 0]])
matDst = np.float32([[50, 50], [150, height - 100], [width - 100, 150]])
matAffine = cv2.getAffineTransform(matSrc, matDst)
dst = cv2.warpAffine(src, matAffine, (width, height))

cv2.imshow("dst", dst)
cv2.waitKey(0)

效果：