Abstract: After a binary image is transformed by the Hough transform under the （ρ,θ） line parameterization,a set of pairs of boundary points in the （ρ,θ） space is chosen.By computing the intersecting points of the lines in the image space,which are determined by the chosen pairs,the bounding polygon of the image objects is obtained.In addition,by determining those pairs of boundary point pairs in the （ρ,θ） space, where the θdifference of two boundary point pairs isπ/2rad but the ρlengths of the two pairs are equal,or their product is minimum,the bounding square or the minimum bounding rectangle are respectively obtained in the same way as for the bounding polygon construction.Furthermore by increasing the number of the edges in the above bounding polygon construction process,an approximate convex hull of object is achieved. Both experimental results and analysis show that our proposed algorithms have good noise-resistance ability and a large range of applicability.