TypeError: Argument given by name ('k') and position (2)

Question

Find below my opencv3 Python3 code to match objects which raises the following error:

TypeError: Argument given by name ('k') and position (2)

Here's the code:

import numpy as np
import cv2
import time
import distance
camera = cv2.VideoCapture(0)
sift = cv2.xfeatures2d.SIFT_create()
img = cv2.imread('/home/shar/bo.jpg')
imgTrainGray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
kpTrain = sift.detect(imgTrainGray,None)
kpTrain, desTrain = sift.compute(imgTrainGray, kpTrain)
FLANN_INDEX_KDTREE = 0
index_params = dict(algorithm = FLANN_INDEX_KDTREE, trees = 5)
search_params = dict(checks=50)  
flann = cv2.FlannBasedMatcher(index_params,search_params)

matches = flann.knnMatch(kpTrain,desTrain,k=2)

Ideas on how to fix it?

Solution 1

This worked for me

FLANN_INDEX_KDTREE = 0
index_params = dict(algorithm = FLANN_INDEX_KDTREE, trees = 5)
search_params = dict(checks=50)

flann = cv2.FlannBasedMatcher(index_params,search_params)
matches = flann.knnMatch(np.asarray(des1,np.float32),np.asarray(des2,np.float32),k=2)

Solution 2

You are trying to match keypoints and the descriptors - which is wrong. You need two images, first you find the keypoints in both of the images (points of interest). Then for each point you calculate a descriptor (again in both images). Finally, you use the Flann to find matches between the two images. See the example here.

Solution 3

Try to pass k as positional argument:

matches = flann.knnMatch(kpTrain,desTrain,2)

Comments

[shar]

TypeError: only length-1 arrays can be converted to Python scalars

[kvorobiev]

@shar What kpTrain and desTrain contains before function call?

[kvorobiev]

@shar Try to use matches = flann.knnMatch(np.asarray(kpTrain,np.float32),np.asarray(des‌​Train,np.float32),2)

[shar]

matches = flann.knnMatch(np.asarray(kpTrain,np.float32),np.asarray(des‌​Train,np.float32),2)‌​‌​ ^ SyntaxError: invalid character in identifier

[kvorobiev]

@shar Can you provide full error traceback in your question? I tried this code and did not get syntax errors

[shar]

File "sk.py", line 16 matches = flann.knnMatch(np.asarray(kpTrain,np.float32),np.asarray(des‌​Train,np.float32),2)‌​‌​ ^ SyntaxError: invalid character in identifier

[kvorobiev]

@shar Ok, lets try to do it in 3 lines: des1 = np.asarray(kpTrain, np.float32) des2 = np.asarray(desTrain, np.float32) matches = flann.knnMatch(des1, des2, 2)‌​

[shar]

File "sk.py", line 18 matches = flann.knnMatch(des1, des2, 2)‌ ^ SyntaxError: invalid character in identifier

[kvorobiev]

@shar Can you share you file?

[kvorobiev]

@shar I have not found in this file line matches = flann.knnMatch(des1, des2, 2)‌. Looks like it's another file

[kvorobiev]

@shar Try just to retype this line matches = flann.knnMatch(des1, des2, 2)‌, without using copy/past

[shar]

File "sk.py", line 16, in <module> des1 = np.asarray(kpTrain, np.float32) File "/usr/local/lib/python3.4/dist-packages/numpy/core/numeric.p‌​y", line 462, in asarray return array(a, dtype, copy=False, order=order) TypeError: float() argument must be a string or a number, not 'cv2.KeyPoint'

[Georg W.]

Can you give any deeper explanation for this error? What is causing it?