项目进度（十二） - SURF算子的应用

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关于SURF算子应用的代码如下：

>>> img = cv2.imread('fly.png',0)

# Create SURF object. You can specify params here or later.
# Here I set Hessian Threshold to 400
>>> surf = cv2.SURF(400)

# Find keypoints and descriptors directly
>>> kp, des = surf.detectAndCompute(img,None)

>>> len(kp)
 699

# Check present Hessian threshold
>>> print surf.hessianThreshold
400.0

# We set it to some 50000. Remember, it is just for representing in picture.
# In actual cases, it is better to have a value 300-500
>>> surf.hessianThreshold = 50000

# Again compute keypoints and check its number.
>>> kp, des = surf.detectAndCompute(img,None)

>>> print len(kp)
47

>>> img2 = cv2.drawKeypoints(img,kp,None,(255,0,0),4)

>>> plt.imshow(img2),plt.show()

# Check upright flag, if it False, set it to True
>>> print surf.upright
False

>>> surf.upright = True

# Recompute the feature points and draw it
>>> kp = surf.detect(img,None)
>>> img2 = cv2.drawKeypoints(img,kp,None,(255,0,0),4)

>>> plt.imshow(img2),plt.show()

提取到的SURF算子特征如下图所示：