After vtk.js' ImageCPRMapper class example is run, how do I get the image coordinates of the center line on the cpr plane in stretch and straighten mode

[flourishing (flourish)]

I see, thank you, I now is to be calculated according to the center line of point upwards or downwards 2.5 mm location of vascular centerline points and normal vector to the tangent plane, according to the (mapper.getCenterlineTangentDirections ()) of the tangent vector to obtain the normal vector doesn’t seem very accurate