display pose next to the the detetcted ArUco marker [closed]

asked 2018-11-17 02:42:38 -0600

Shrijan
6 ●1 ●2

Hi, I'm able to get pose of all the detected markers but i'm not able to display the pose of each marker respectively on the image.

        for i in range(0, self.ids.size):
            #print(self.tvecs[i][0][2])
            cv_image=aruco.drawAxis(cv_image, camera_matrix, camera_distortion, self.rvecs[i], self.tvecs[i], 10)
            #str_position = "trans"%((self.tvecs[i][0]))

            str_position = "MARKER Position x=%4.0f  y=%4.0f  z=%4.0f"%(self.tvecs[i][0][0], self.tvecs[i][0][1], self.tvecs[i][0][2])
            #cv2.putText(cv_image, str_position, (0, 100), font, 1, (0, 255, 0), 2, cv2.LINE_AA)
            cv2.putText(cv_image, "{:.2f}".format(str_position), (0,100), font, 4,(255,255,255), 2, cv2.LINE_AA)

        #print(i)
        cv2.imshow("Image window", cv_image)
        cv2.waitKey(1)

image description

So, anybody knows how to get the respective (x,y) position of the detected markers and then use cv2.putText?

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Closed for the following reason the question is answered, right answer was accepted by Shrijan
close date 2018-11-17 04:08:52.203293

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the interesting part here is: the tvec holds a 3d space position, but to draw it, we would need it's 2d (screen) projection.

maybe we need to look into what drawAxis() does there ?

berak ( 2018-11-17 02:44:34 -0600 )edit

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answered 2018-11-17 03:01:55 -0600

berak
32993 ●7 ●81 ●312

updated 2018-11-17 04:14:25 -0600

it gets slightly advanced here, but to find the 2d position of your marker on the screen, you have to project it from the 3d space of the rvec / tvec back to 2d, in the very same way, drawAxis() does it.

untested (i don't have any aruco markers), but something like this:

# a list with a single point in it (relative to the tvec position):
# maybe you want some x or y offset, so it does not interfere with drawAxis() !
pt = np.array([[-12, -12, 0]], dtype=np.float)
imgpts, _ = cv2.projectPoints(pt, self.rvecs[i], self.tvecs[i], camera_matrix, dist_coeffs)
cv2.putText(cv_image, imgpts[0][0], sometext, ...)

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On printing the imgpts i get

('Image points', (array([[[ 363.90325111,  151.41181538]]]), array([[  0.00000000e+00,   0.00000000e+00,   0.00000000e+00,
      5.44941343e+00,  -1.73800790e-02,  -4.86394205e-01,
      8.92040663e-02,   0.00000000e+00,   1.00000000e+00,
      0.00000000e+00,   1.18684255e+00,   2.66874705e-02,
     -1.27499178e+01,   2.27360909e+01,   6.00097359e-04],
   [  0.00000000e+00,   0.00000000e+00,   0.00000000e+00,
     -1.74236032e-02,   5.47465181e+00,   6.62782315e-01,
      0.00000000e+00,  -1.21241734e-01,   0.00000000e+00,
      1.00000000e+00,  -1.61702849e+00,  -3.63606781e-02,
      3.07593893e+01,  -1.27818469e+01,  -8.17610155e-04]])))

Probably i'll try to find the x,y co-ordinates from the detected corners array

Shrijan ( 2018-11-17 03:24:23 -0600 )edit

@Shrijan thanks for reporting back !

ok, my bad, got the projectPoints signature wrong (it also returns jacobians)

please see updated answer !

berak ( 2018-11-17 03:27:47 -0600 )edit

Ahh, it works. Just changed a bit while doing cv2.putText.Have to play with offset only now..Thanks alot.

pt =np.array([[-12, -12, 0]], dtype=np.float)

        #for rvec, tvec in zip(self.rvecs, self.tvecs):
        for i in range(0, self.ids.size):
            #print(self.tvecs[i][0][2])
            cv_image=aruco.drawAxis(cv_image, camera_matrix, camera_distortion, self.rvecs[i], self.tvecs[i], 10)
            #str_position = "trans"%((self.tvecs[i][0]))
            imgpts,_ = cv2.projectPoints(pt, self.rvecs[i], self.tvecs[i], camera_matrix, camera_distortion)
            #print("Image points",imgpts[0][0][1])

            str_position = "MARKER Position x=%4.0f  y=%4.0f  z=%4.0f"%(self.tvecs[i][0][0], self.tvecs[i][0][1], self.tvecs[i][0][2])
            cv2.putText(cv_image, str_position, (int(imgpts[0][0][0]),int(imgpts[0][0][1])), font, 1,

Shrijan ( 2018-11-17 04:06:32 -0600 )edit

oh, np.array, not a simple list ;)

berak ( 2018-11-17 04:13:53 -0600 )edit

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display pose next to the the detetcted ArUco marker [closed]

Closed for the following reason the question is answered, right answer was accepted by Shrijan
close date 2018-11-17 04:08:52.203293

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display pose next to the the detetcted ArUco marker [closed] edit

Closed for the following reason the question is answered, right answer was accepted by Shrijan close date 2018-11-17 04:08:52.203293

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display pose next to the the detetcted ArUco marker [closed]

Closed for the following reason the question is answered, right answer was accepted by Shrijan
close date 2018-11-17 04:08:52.203293