OpenCV - SIFT/SURF

OpenCV - SIFT/SURF Python

1.OpenCV中使用SIFT首先安装的包：
打开终端安装：sudo pip install opencv-contrib-python==3.4.2.16 新版的opencv可能没有xfeatures2d。
2. SIFT提取特征：用于检测斑点，使用difference of Gaussians(DoG)

import cv2
from matplotlib import pyplot as plt

path = '9.jpg'
img = cv2.imread(path)
img1 = cv2.imread(path)
plt.imshow(img)  #图1
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
sift = cv2.xfeatures2d.SIFT_create()
#得到特征点
keypoints, descriptor = sift.detectAndCompute(gray, None)

img = cv2.drawKeypoints(image=img1, outImage=img, keypoints=keypoints, flags = cv2.DRAW_MATCHES_FLAGS_DRAW_RICH_KEYPOINTS, color=(51, 163, 236))
plt.imshow(img)  #图2

img = cv2.drawKeypoints(image=img1, outImage=img, keypoints=keypoints, flags = cv2.DRAW_MATCHES_FLAGS_DRAW_OVER_OUTIMG, color=(51, 163, 236))
plt.imshow(img) #图3

img = cv2.drawKeypoints(image=img1, outImage=img, keypoints=keypoints, flags = cv2.DRAW_MATCHES_FLAGS_NOT_DRAW_SINGLE_POINTS, color=(51, 163, 236))
plt.imshow(img) #图4

img = cv2.drawKeypoints(image=img1, outImage=img, keypoints=keypoints, flags = cv2.DRAW_MATCHES_FLAGS_DEFAULT, color=(51, 163, 236))
plt.imshow(img) #图5

图2-5主要是改变了cv2.drawKeypoints()中的flags的参数，不同的参数表示不同的显示效果

flags = cv2.DRAW_MATCHES_FLAGS_DEFAULT：创建输出图像矩阵，使用现存的输出图像绘制匹配对和特征点，对每一个关键点只绘制中间点
flags = cv2.DRAW_MATCHES_FLAGS_DRAW_OVER_OUTIMG：不创建输出图像矩阵，而是在输出图像上绘制匹配对
flags = cv2.DRAW_MATCHES_FLAGS_DRAW_RICH_KEYPOINTS：对每一个特征点绘制带大小和方向的关键点图形
flags = cv2.DRAW_MATCHES_FLAGS_NOT_DRAW_SINGLE_POINTS：单点的特征点不被绘制

color 表示标注的颜色

图1
图2
图3
图4
图5
3.SURF检测斑点，使用Hessian算法

surf = cv2.xfeatures2d.SURF_create()
keypoints, descriptor = surf.detectAndCompute(gray, None)
img = cv2.drawKeypoints(image=img1, outImage=img, keypoints=keypoints, flags = cv2.DRAW_MATCHES_FLAGS_DRAW_RICH_KEYPOINTS, color=(51, 163, 236))
plt.imshow(img)   #图6
img = cv2.drawKeypoints(image=img1, outImage=img, keypoints=keypoints, flags = cv2.DRAW_MATCHES_FLAGS_DRAW_OVER_OUTIMG, color=(51, 163, 236))
plt.imshow(img)
img = cv2.drawKeypoints(image=img1, outImage=img, keypoints=keypoints, flags = cv2.DRAW_MATCHES_FLAGS_NOT_DRAW_SINGLE_POINTS, color=(51, 163, 236))
plt.imshow(img)
img = cv2.drawKeypoints(image=img1, outImage=img, keypoints=keypoints, flags = cv2.DRAW_MATCHES_FLAGS_DEFAULT, color=(51, 163, 236))
plt.imshow(img)

图6