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

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?

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 (Nov 17 '18)edit

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answered Nov 17 '18

berak
32993 ●7 ●81 ●312

updated Nov 17 '18

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, ...)

Comments

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 (Nov 17 '18)edit

@Shrijan thanks for reporting back !

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

please see updated answer !

berak (Nov 17 '18)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 (Nov 17 '18)edit

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

berak (Nov 17 '18)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 savecancel

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