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WarpAffine blurs the image

asked 2018-08-08 03:03:28 -0500

Raki gravatar image

updated 2018-08-08 03:14:40 -0500

I am trying to rotate an image based on the rotation matrix I get from the camera. It does it good, however at every loop my image gets more blurry. What might be the reason? I've tried all the tags of WarpAffine, no luck. Here is my code:

        toBeRotatedShuttle = shuttleIcon.copy()
        rows, cols, w = toBeRotatedShuttle.shape
        angle = get_camera_rotation(smoothenedMatrix)
        angleInDegrees = round(math.degrees(math.asin(angle)),2) # convert radian to degrees
        rotationMatrix = cv2.getRotationMatrix2D((cols / 2, rows / 2), angleInDegrees, 1)
        shuttleIcon = cv2.warpAffine(toBeRotatedShuttle, rotationMatrix, (cols, rows), cv2.INTER_AREA)

and here is my rotation matrix function:

'''Takes 2 vectors and returns the rotation matrix between these 2 vectors'''
def get_camera_rotation(homographyMatrix):
    # Points in the camera frame
    camera_pts = np.float32([[round(CAM_WIDTH / 2), round(CAM_HEIGHT / 2)],
                             [round(10 + CAM_WIDTH / 2), round(10 + CAM_HEIGHT / 2)]]).reshape(-1, 1, 2)
    # Find these points in the projector image
    proj_pts = cv2.perspectiveTransform(camera_pts, homographyMatrix)

    # Find the vectors between the sets of points
    camera_vector = (camera_pts[0][0][0] - camera_pts[1][0][0], camera_pts[0][0][1] - camera_pts[1][0][1])
    proj_vector = (proj_pts[0][0][0] - proj_pts[1][0][0], proj_pts[0][0][1] - proj_pts[1][0][1])

    # change the vectors to unit vectors
    camera_vector = camera_vector / np.absolute(np.linalg.norm(camera_vector))
    proj_vector = proj_vector / np.absolute(np.linalg.norm(proj_vector))

    # calculate the angle between the 2 vectors
    # Change the sign of the angle if the rocket is turning the opposite way to desired
    #sine of the angle
    sinAngle = camera_vector[0] * proj_vector[1] - camera_vector[1] * proj_vector[0]
    #angle between the vectors
    angle = np.arcsin(np.clip(sinAngle, -1.0, 1.0))

    #print("The angle between the camera and the projector is:")
    #print(angle)
    # calculate the 2D rotation matrix from this angle
    rotation_matrix = np.matrix([[np.cos(angle), -1 * np.sin(angle)], [np.sin(angle), np.cos(angle)]])
    return angle

Any thoughts?

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answered 2018-08-08 03:18:47 -0500

Raki gravatar image

OK. I've found my mistake. I had the wrong copy of my image.

The following prevents blurring, in case if someone out there still needs it:

# rotate the shuttle as the camera does
# first though, get a copy
toBeRotatedShuttle = shuttleIcon.copy()
rows, cols, w = toBeRotatedShuttle.shape
angle = get_camera_rotation(smoothenedMatrix)
angleInDegrees = round(math.degrees(math.asin(angle)), 2)  # convert radian to degrees
rotationMatrix = cv2.getRotationMatrix2D((cols / 2, rows / 2), angleInDegrees, 1)
toBeRotatedShuttle = cv2.warpAffine(toBeRotatedShuttle, rotationMatrix, (cols, rows), cv2.INTER_LANCZOS4)

# Overlay transparent images at desired postion(x,y) and Scale.
process_the_image(toBeRotatedShuttle)
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Asked: 2018-08-08 03:03:28 -0500

Seen: 111 times

Last updated: Aug 08 '18