the object dimensions. During the marker detection step, a homo graphy H is calculated which essentially maps the marker in the image to the undistorted view of the marker(a plane-to-plane mapping [6]). This homography H is used to define a rectangular region of interest (ROI) within the original image to reduce the amount of data for segmentation and to facilitate parameter selection. Note that we do not rectify the image prior to segmentation. The final results are acquired by local adaptive thresholding and applying a set of morphological operations on a grey scale input image: