9. ALGORITHM Modified Moore’s neighbor algorithm Input : A square tessellation T containing a connected component P of black cells. Output : A sequence B(b 1 , b 2 , …, b k ) of boundary pixels i.e. the contour line. We define M(p) to be the Moore neighborhood of pixel p , c denotes the current pixel under consideration i.e. c is in M(p) . Begin Set B to be empty. From bottom to top and left to right scan the cells of T until a black pixel, s, of P is found. Insert s in B. Set the current boundary point, p, to s i.e. p = s. Set c to be the next clockwise pixel in M(p). While c is not in B do If c is black Insert c in B. Set p=c. End if Advance c to the next clockwise pixel in M(p). End while Set p=s. Set c to the next anticlockwise pixel in M(p). Repeat previous step with an anticlockwise scan each time in M(p). End.

11. RESULT / OUTPUT Sample Topographic Sheet Contour Extraction from Sample Image

12. Input image (before thinning) Output image (after thinning) THINNING

13. Contour Tracing Method

14. Contour Tracing Input Output From Contour Tracing

15. DATABASE