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Distinguishing Image Similarities Using Frechet Metric

Esmradi, Aysan | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51855 (02)
  4. University: Sharif University of Technology
  5. Department: Mathematical Sciences
  6. Advisor(s): Mahdavi-Amiri, Nezam
  7. Abstract:
  8. Automatic recognition of input characters and distinguishing image similarities have been of high interest specially as computer systems have become widely popular in industries and businesses. In this thesis, we present a method based on the Frechet distance for automatic character and image recognition. Frechet distance is a measure of similarity between polygon curves. The presented approach in this thesis is based on the work of Maheshvari,et.al.We first provide a literature review on the existing techniques, emphasizing the superior performance of rule-based algorithms, and introducing the different types of Frechet distances based on the characteristics of the input geometry. Then, we propose a method for automatic character recognition based on computation of the Frechet distance having speed limitation inO(n^2Log2n) time.Since the input is a graphical image and has more than one pixel, image simplification needs to be performed in order to allow for comparison with the available databases using the Frechet distance. To do so, we propose a four-stage algorithm: ( 1) calculating the closed polygon curve from the input image, (2 ) extracting the skeleton from the closed polygon curve, ( 3) simplification for comparison purposes, and (4 ) matching with the original input. This algorithm has been implemented and demonstrated on two different input samples of handwritings. Finally, we perform a comparison between the Frechet distance and the Frechet distance with speed limitation.We conclude that despite the shorter computing time compared to the Frechet distance, and larger distance compared to the classic Frechet distance, the Frechet distance with speed limitation is more suitable for input character recognition due to its movement limitations along the sides of the polygon
  9. Keywords:
  10. Image Processing ; Frechet Distance Problem ; Frechet Distance with Speed Limitation ; Polygon Curve Simplification ; Polygonal Curve

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