SUPPORTING LANDMARK IMAGE RETRIEVAL WITH SKYLINE EXTRACTION TECHNIQUES Date : 2012 / 04 / 12 資訊碩一 LAB603

Outline  Introduction  Preliminaries  Method  Experimental result  Conclusions

Introduction  Image retrieval have more challenge than text retrieval.  Use low-level feature to identify objects is non- trivial.  Skyline is a good feature to identify landmark contour.

Outline  Introduction  Preliminaries  Method  Experimental result  Conclusions

Traditional image retrieval  Traditional techniques for image retrieval rely on some metadata (i.e., keywords or captions of image)  It isn’t a good method for practical applications since it is labor intensive and need more space.

Content-based image retrieval  Content-based image retrieval(CBIR) is using image’s feature for retrieval.  Query-by-example  Query-by-sketch  Relevance feedback technique

Identifying landmarks with skylines  Region-growing-based  Using same color region extend find the skylines  Weak robustness on the sky with cloud or complex background  Edge-based  Edge detection  Retaining the points which are luminous intensity change sharply  Using other method to find clear skyline.

Outline  Introduction  Preliminaries  Method  Experimental result  Conclusions

Method(1/4) - Difficulties  Small portion of edge points constitute the proper skyline.  Skyline may not fully-connected.  Steep or tortuous.

Method(2/4) - RON  RON(radius of neighborhood)  Defining the search region (ex. RON = 2 -> grid zone = 5*5)  Solving the difficulties.

Method(3/4) – Direction priority  Using clockwise  Good direction for traversal skyline.

Method(4/4) – Find the skyline  Using Sobel Filter for edge detection  Using DFS for search. (Need decide the start point?)

Outline  Introduction  Preliminaries  Method  Experimental result  Conclusions

Experimental Result  DP VS This method ( O(n 2 ) & O(n) )

Outline  Introduction  Preliminaries  Method  Experimental result  Conclusions

Conclusions  This is a feasible for landmark image retrieval.  If there are more line cross the image?  If sky have complex object(ex. Light or cloud…)?  If the beginning point is not in skyline?  More problem need to solving…

Thank for your listening!  Q&A