An Improved Shape Descriptor Using Bezier Curves Authors: Ferdous Ahmed Sohel Dr. Gour Chandra Karmakar Professor Laurence Sean Dooley Gippsland School of Information Technology

2 ISDBC: Presentation Outline Introduction. Existing Bezier curve based shape descriptors. Proposed ISDBC –Control point determination. –Control point coding. Results. Conclusions.

3 Introduction …0110…010100… Shape Descriptor Shape Coding: Applications:  Communication: Mobile multimedia communication, low bit rate coding.  Storage and retrieval: Digital library, indexing, digital archiving.  Interactive editing: Cartoons, digital films.

4 Existing shape descriptor using BC Object shape description by Cinque et al (1998).  Divides the shape into equal segments in terms of number of boundary points.  Easy and simple.  Considers encoding of the control points.  Does not consider the shape information.  The coding is not efficient.

5 Existing shape descriptor using BC Chinese calligraphic character descriptor by Yang et al (2001).  Uses trial-and-error methods.  The control points are highly depended on direction of the shape at the segment-ends.  Does not consider the encoding.  Allows the control point be out side the shape.  Considers the shape information.

6 Existing shape descriptor using BC Arabic character descriptor by Sarfraz and Khan (2002, 2003).  Does not consider the encoding.  Allows the control point be out side the shape.  Considers the shape information.  Optimally selects the control points in the distortion sense.

7 Existing shape descriptor using BC Active shape lip model by Shdaifa et al (2003).  Easy and simple.  The control points are highly depended on direction of the shape at the segment-ends.  Does not consider the encoding.  Allows the control point be out side the shape.

8 Existing shape descriptor using BC Generic shape descriptor by Sohel et al (2005).  Weak for the shapes having loops or repeated or branches.  Considers the shape information.  Uses efficient dynamic fixed length coding ( DFLC) method.  Control points are with in the range of shape points Also the algorithm by Cinque et al is weak for loops and branches!

9 Proposed ISDBC Control point calculation –Divide the shape into segments. –Find the significant points. –Insert supplementary points. –Form the potential control point set. –Determine the control points. Control points encoding –Encoded differentially by modified DFLC.

10 ISDBC For the i th segment |B i |: number of potential control points. b I : set of potential control points.

11 ISDBC Control point coding 1 st point l1l1 2*l 1 l1l1 lili 2*l i lili … ljlj 2*l j First SegmentNext segment…Last Segment  Distance between consecutive control points is periodic. 1 st point l2*lll l … l z (=4l): maximum number of potential control points of a segment.

12 ISDBC Dynamic fixed length coding (DFLC) —A combination of run-length code and chain code. —Encodes the control points differentially. —Differential Direction is encoded by 8-bits. —The distance is the run- length. P Q

13 ISDBC The complete shape descriptor 4- bit for length of L 1 1 st point Dir + L 1 Dir + L 2 Dir + L 1 Dir + L 1 Dir + L 2 Dir + L 1 …Dir + L 1 Dir + L 2 First SegmentNext segment…Last Segment  The starting 4 bits are reserved for the length of L 1.  ISDBC can encode a segment of up to 4*2 16 shape points.

14 Results Distortion measure [1] Class 1: Peak distortion (Max) Class 2: Mean Square distortion (MS) [1] F.A. Sohel, L.S. Dooley, and G.C. Karmakar, “Accurate distortion measurement for generic shape coding,” Pattern Recognition Letters, Elsevier Science Inc., in press, available on-line.

15 Results ISDBC

16 Results

17 Results Shape  BreamArabicLip Techniques  D max D MS D Max D MS D Max D MS ISDBC Sohel et al Cinque et al Sarfraz Yang et al Shdaifat et al Distortion in different shapes by the techniques.

18 Results Shape Techniques SR = 5SR = 6SR = 7SR =8 Bream ISDBC SDBC Cinque et al Lip ISDBC SDBC Cinque et al Bit requirements 20% improvement in the descriptor size. 23% reduction in the descriptor length for each additional segment.

19 Conclusion ISDBC utilises the domain specific shape information both in  Dividing the shape into segments  Determining the control points. Keeps the distortion lower. Efficiently encode the control points.

20 Thank you