how to extract x,y coordinates from OpenCV “cv2.keypoint” object?

I tried to use the following code:

    xCoordinate=point.x

(point is type of cv2.keyPoint)
It gives me error saying cv2.keyPoint has no attribute 'x'

asked Mar 9 '16 at 6:21

mengmengxyz

1442510

add a comment |

I tried to use the following code:

    xCoordinate=point.x

(point is type of cv2.keyPoint)
It gives me error saying cv2.keyPoint has no attribute 'x'

asked Mar 9 '16 at 6:21

mengmengxyz

1442510

add a comment |

I tried to use the following code:

    xCoordinate=point.x

(point is type of cv2.keyPoint)
It gives me error saying cv2.keyPoint has no attribute 'x'

asked Mar 9 '16 at 6:21

mengmengxyz

1442510

I tried to use the following code:

    xCoordinate=point.x

(point is type of cv2.keyPoint)
It gives me error saying cv2.keyPoint has no attribute 'x'

python opencv numpy

asked Mar 9 '16 at 6:21

mengmengxyz

1442510

asked Mar 9 '16 at 6:21

mengmengxyz

1442510

asked Mar 9 '16 at 6:21

mengmengxyz

1442510

asked Mar 9 '16 at 6:21

mengmengxyz

1442510

asked Mar 9 '16 at 6:21

mengmengxyz

1442510

add a comment |

5 Answers
5

active

oldest

votes

You can use:

import numpy as np



pts = np.float([kp[idx].pt for idx in len(kp)]).reshape(-1, 1, 2)

pts will be an array of keypoints.

answered Mar 9 '16 at 8:40

Francesco Nazzaro

1,809617

add a comment |

point.pt is a tuple(x,y)`.

So,

x = point.pt[0]

y = point.pt[1]

or,

(x,y) = point.pt

edited Dec 22 '18 at 4:45

skumhest

answered May 6 '17 at 8:13

saikat sarkar

9114

add a comment |

Read the docs.

class KeyPoint

Data structure for salient point detectors.

Point2f pt
-- coordinates of the keypoint

float size
-- diameter of the meaningful keypoint neighborhood

float angle ...¶

So point.pt is a Point2f.

Try x,y= point.pt

edited Nov 20 '18 at 2:05

answered Mar 9 '16 at 6:37

roadrunner66

3,74321834

point.pt.x is invalid, please correct it as: x, y = point.pt

– Nirmal
Oct 26 '18 at 5:30

add a comment |

Here is my take (runable code):

import cv2, os

import numpy as np

import matplotlib.pyplot as plt



# INITIALISATION

filename = os.path.join('foo', 'bar.jpg')

img0 = cv2.imread(filename) # original image

gray = cv2.cvtColor(img0, cv2.COLOR_BGR2GRAY) # convert to grayscale

sift = cv2.xfeatures2d.SIFT_create() # initialize SIFT 

f, (ax1, ax2) = plt.subplots(1, 2) # create subplots



# DETECT AND DRAW KEYPOINTS

# sift.detect() returns a list of keypoints

# keypoint is a standard class of opencv (not just SIFT-related)

kp = sift.detect(gray,None) # calculates SIFT points

img1=cv2.drawKeypoints(gray,kp, None) # mae new image with keypoints drawn

ax1.imshow(img1) # plot 



# RETREIVE KEYPOINTS COORDINATES AND DRAW MANUALLY

# Reade these and make numpy array

pts = np.asarray([[p.pt[0], p.pt[1]] for p in kp])

cols = pts[:,0]

rows = pts[:,1]

ax2.imshow(cv2.cvtColor(img0, cv2.COLOR_BGR2RGB))

ax2.scatter(cols, rows)



plt.show()

edited Nov 2 '18 at 12:58

answered Nov 2 '18 at 10:40

quickbug

1,65931117

add a comment |

I solved your problem like this.

kp,des = surf.detectAndCompute(img,None) 

pts = [p.pt for p in kp]

Now you get a list of x,y co-ordinates for all keypoints in your image.

edited Oct 6 '17 at 9:06

Shaido

12.6k122541

answered Oct 6 '17 at 8:49

Alexander Hunt

add a comment |

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5 Answers
5

active

oldest

votes

5 Answers
5

active

oldest

votes

You can use:

import numpy as np



pts = np.float([kp[idx].pt for idx in len(kp)]).reshape(-1, 1, 2)

pts will be an array of keypoints.

answered Mar 9 '16 at 8:40

Francesco Nazzaro

1,809617

add a comment |

You can use:

import numpy as np



pts = np.float([kp[idx].pt for idx in len(kp)]).reshape(-1, 1, 2)

pts will be an array of keypoints.

answered Mar 9 '16 at 8:40

Francesco Nazzaro

1,809617

add a comment |

You can use:

import numpy as np



pts = np.float([kp[idx].pt for idx in len(kp)]).reshape(-1, 1, 2)

pts will be an array of keypoints.

answered Mar 9 '16 at 8:40

Francesco Nazzaro

1,809617

You can use:

import numpy as np



pts = np.float([kp[idx].pt for idx in len(kp)]).reshape(-1, 1, 2)

pts will be an array of keypoints.

answered Mar 9 '16 at 8:40

Francesco Nazzaro

1,809617

answered Mar 9 '16 at 8:40

Francesco Nazzaro

1,809617

answered Mar 9 '16 at 8:40

Francesco Nazzaro

1,809617

answered Mar 9 '16 at 8:40

Francesco Nazzaro

1,809617

add a comment |

point.pt is a tuple(x,y)`.

So,

x = point.pt[0]

y = point.pt[1]

or,

(x,y) = point.pt

edited Dec 22 '18 at 4:45

skumhest

answered May 6 '17 at 8:13

saikat sarkar

9114

add a comment |

point.pt is a tuple(x,y)`.

So,

x = point.pt[0]

y = point.pt[1]

or,

(x,y) = point.pt

edited Dec 22 '18 at 4:45

skumhest

answered May 6 '17 at 8:13

saikat sarkar

9114

add a comment |

point.pt is a tuple(x,y)`.

So,

x = point.pt[0]

y = point.pt[1]

or,

(x,y) = point.pt

edited Dec 22 '18 at 4:45

skumhest

answered May 6 '17 at 8:13

saikat sarkar

9114

point.pt is a tuple(x,y)`.

So,

x = point.pt[0]

y = point.pt[1]

or,

(x,y) = point.pt

edited Dec 22 '18 at 4:45

skumhest

answered May 6 '17 at 8:13

saikat sarkar

9114

edited Dec 22 '18 at 4:45

skumhest

edited Dec 22 '18 at 4:45

skumhest

edited Dec 22 '18 at 4:45

skumhest

answered May 6 '17 at 8:13

saikat sarkar

9114

answered May 6 '17 at 8:13

saikat sarkar

9114

answered May 6 '17 at 8:13

saikat sarkar

9114

add a comment |

Read the docs.

class KeyPoint

Data structure for salient point detectors.

Point2f pt
-- coordinates of the keypoint

float size
-- diameter of the meaningful keypoint neighborhood

float angle ...¶

So point.pt is a Point2f.

Try x,y= point.pt

edited Nov 20 '18 at 2:05

answered Mar 9 '16 at 6:37

roadrunner66

3,74321834

point.pt.x is invalid, please correct it as: x, y = point.pt

– Nirmal
Oct 26 '18 at 5:30

add a comment |

Read the docs.

class KeyPoint

Data structure for salient point detectors.

Point2f pt
-- coordinates of the keypoint

float size
-- diameter of the meaningful keypoint neighborhood

float angle ...¶

So point.pt is a Point2f.

Try x,y= point.pt

edited Nov 20 '18 at 2:05

answered Mar 9 '16 at 6:37

roadrunner66

3,74321834

point.pt.x is invalid, please correct it as: x, y = point.pt

– Nirmal
Oct 26 '18 at 5:30

add a comment |

Read the docs.

class KeyPoint

Data structure for salient point detectors.

Point2f pt
-- coordinates of the keypoint

float size
-- diameter of the meaningful keypoint neighborhood

float angle ...¶

So point.pt is a Point2f.

Try x,y= point.pt

edited Nov 20 '18 at 2:05

answered Mar 9 '16 at 6:37

roadrunner66

3,74321834

Read the docs.

class KeyPoint

Data structure for salient point detectors.

Point2f pt
-- coordinates of the keypoint

float size
-- diameter of the meaningful keypoint neighborhood

float angle ...¶

So point.pt is a Point2f.

Try x,y= point.pt

edited Nov 20 '18 at 2:05

answered Mar 9 '16 at 6:37

roadrunner66

3,74321834

edited Nov 20 '18 at 2:05

answered Mar 9 '16 at 6:37

roadrunner66

3,74321834

answered Mar 9 '16 at 6:37

roadrunner66

3,74321834

answered Mar 9 '16 at 6:37

roadrunner66

3,74321834

point.pt.x is invalid, please correct it as: x, y = point.pt

– Nirmal
Oct 26 '18 at 5:30

add a comment |

point.pt.x is invalid, please correct it as: x, y = point.pt

– Nirmal
Oct 26 '18 at 5:30

point.pt.x is invalid, please correct it as: x, y = point.pt

– Nirmal
Oct 26 '18 at 5:30

add a comment |

Here is my take (runable code):

import cv2, os

import numpy as np

import matplotlib.pyplot as plt



# INITIALISATION

filename = os.path.join('foo', 'bar.jpg')

img0 = cv2.imread(filename) # original image

gray = cv2.cvtColor(img0, cv2.COLOR_BGR2GRAY) # convert to grayscale

sift = cv2.xfeatures2d.SIFT_create() # initialize SIFT 

f, (ax1, ax2) = plt.subplots(1, 2) # create subplots



# DETECT AND DRAW KEYPOINTS

# sift.detect() returns a list of keypoints

# keypoint is a standard class of opencv (not just SIFT-related)

kp = sift.detect(gray,None) # calculates SIFT points

img1=cv2.drawKeypoints(gray,kp, None) # mae new image with keypoints drawn

ax1.imshow(img1) # plot 



# RETREIVE KEYPOINTS COORDINATES AND DRAW MANUALLY

# Reade these and make numpy array

pts = np.asarray([[p.pt[0], p.pt[1]] for p in kp])

cols = pts[:,0]

rows = pts[:,1]

ax2.imshow(cv2.cvtColor(img0, cv2.COLOR_BGR2RGB))

ax2.scatter(cols, rows)



plt.show()

edited Nov 2 '18 at 12:58

answered Nov 2 '18 at 10:40

quickbug

1,65931117

add a comment |

Here is my take (runable code):

import cv2, os

import numpy as np

import matplotlib.pyplot as plt



# INITIALISATION

filename = os.path.join('foo', 'bar.jpg')

img0 = cv2.imread(filename) # original image

gray = cv2.cvtColor(img0, cv2.COLOR_BGR2GRAY) # convert to grayscale

sift = cv2.xfeatures2d.SIFT_create() # initialize SIFT 

f, (ax1, ax2) = plt.subplots(1, 2) # create subplots



# DETECT AND DRAW KEYPOINTS

# sift.detect() returns a list of keypoints

# keypoint is a standard class of opencv (not just SIFT-related)

kp = sift.detect(gray,None) # calculates SIFT points

img1=cv2.drawKeypoints(gray,kp, None) # mae new image with keypoints drawn

ax1.imshow(img1) # plot 



# RETREIVE KEYPOINTS COORDINATES AND DRAW MANUALLY

# Reade these and make numpy array

pts = np.asarray([[p.pt[0], p.pt[1]] for p in kp])

cols = pts[:,0]

rows = pts[:,1]

ax2.imshow(cv2.cvtColor(img0, cv2.COLOR_BGR2RGB))

ax2.scatter(cols, rows)



plt.show()

edited Nov 2 '18 at 12:58

answered Nov 2 '18 at 10:40

quickbug

1,65931117

add a comment |

Here is my take (runable code):

import cv2, os

import numpy as np

import matplotlib.pyplot as plt



# INITIALISATION

filename = os.path.join('foo', 'bar.jpg')

img0 = cv2.imread(filename) # original image

gray = cv2.cvtColor(img0, cv2.COLOR_BGR2GRAY) # convert to grayscale

sift = cv2.xfeatures2d.SIFT_create() # initialize SIFT 

f, (ax1, ax2) = plt.subplots(1, 2) # create subplots



# DETECT AND DRAW KEYPOINTS

# sift.detect() returns a list of keypoints

# keypoint is a standard class of opencv (not just SIFT-related)

kp = sift.detect(gray,None) # calculates SIFT points

img1=cv2.drawKeypoints(gray,kp, None) # mae new image with keypoints drawn

ax1.imshow(img1) # plot 



# RETREIVE KEYPOINTS COORDINATES AND DRAW MANUALLY

# Reade these and make numpy array

pts = np.asarray([[p.pt[0], p.pt[1]] for p in kp])

cols = pts[:,0]

rows = pts[:,1]

ax2.imshow(cv2.cvtColor(img0, cv2.COLOR_BGR2RGB))

ax2.scatter(cols, rows)



plt.show()

edited Nov 2 '18 at 12:58

answered Nov 2 '18 at 10:40

quickbug

1,65931117

Here is my take (runable code):

import cv2, os

import numpy as np

import matplotlib.pyplot as plt



# INITIALISATION

filename = os.path.join('foo', 'bar.jpg')

img0 = cv2.imread(filename) # original image

gray = cv2.cvtColor(img0, cv2.COLOR_BGR2GRAY) # convert to grayscale

sift = cv2.xfeatures2d.SIFT_create() # initialize SIFT 

f, (ax1, ax2) = plt.subplots(1, 2) # create subplots



# DETECT AND DRAW KEYPOINTS

# sift.detect() returns a list of keypoints

# keypoint is a standard class of opencv (not just SIFT-related)

kp = sift.detect(gray,None) # calculates SIFT points

img1=cv2.drawKeypoints(gray,kp, None) # mae new image with keypoints drawn

ax1.imshow(img1) # plot 



# RETREIVE KEYPOINTS COORDINATES AND DRAW MANUALLY

# Reade these and make numpy array

pts = np.asarray([[p.pt[0], p.pt[1]] for p in kp])

cols = pts[:,0]

rows = pts[:,1]

ax2.imshow(cv2.cvtColor(img0, cv2.COLOR_BGR2RGB))

ax2.scatter(cols, rows)



plt.show()

edited Nov 2 '18 at 12:58

answered Nov 2 '18 at 10:40

quickbug

1,65931117

edited Nov 2 '18 at 12:58

answered Nov 2 '18 at 10:40

quickbug

1,65931117

answered Nov 2 '18 at 10:40

quickbug

1,65931117

answered Nov 2 '18 at 10:40

quickbug

1,65931117

add a comment |

I solved your problem like this.

kp,des = surf.detectAndCompute(img,None) 

pts = [p.pt for p in kp]

Now you get a list of x,y co-ordinates for all keypoints in your image.

edited Oct 6 '17 at 9:06

Shaido

12.6k122541

answered Oct 6 '17 at 8:49

Alexander Hunt

add a comment |

I solved your problem like this.

kp,des = surf.detectAndCompute(img,None) 

pts = [p.pt for p in kp]

Now you get a list of x,y co-ordinates for all keypoints in your image.

edited Oct 6 '17 at 9:06

Shaido

12.6k122541

answered Oct 6 '17 at 8:49

Alexander Hunt

add a comment |

I solved your problem like this.

kp,des = surf.detectAndCompute(img,None) 

pts = [p.pt for p in kp]

Now you get a list of x,y co-ordinates for all keypoints in your image.

edited Oct 6 '17 at 9:06

Shaido

12.6k122541

answered Oct 6 '17 at 8:49

Alexander Hunt

I solved your problem like this.

kp,des = surf.detectAndCompute(img,None) 

pts = [p.pt for p in kp]

Now you get a list of x,y co-ordinates for all keypoints in your image.

edited Oct 6 '17 at 9:06

Shaido

12.6k122541

answered Oct 6 '17 at 8:49

Alexander Hunt

edited Oct 6 '17 at 9:06

Shaido

12.6k122541

edited Oct 6 '17 at 9:06

Shaido

12.6k122541

edited Oct 6 '17 at 9:06

Shaido

12.6k122541

answered Oct 6 '17 at 8:49

Alexander Hunt

answered Oct 6 '17 at 8:49

Alexander Hunt

answered Oct 6 '17 at 8:49

Alexander Hunt

add a comment |

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