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Image Vectorization

Image Vectorization. Cai Qingzhong 2007/11/01. What is Vectorization?. Image Vectorization. Goal convert a raster image into a vector graphics vector graphics include points lines curves polygons …. Why Vector Graphics. Compact Scalable Editable Easy to animate. Compact.

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Image Vectorization

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  1. Image Vectorization Cai Qingzhong 2007/11/01

  2. What is Vectorization?

  3. Image Vectorization • Goal • convert a raster image into a vector graphics • vector graphics include • points • lines • curves • polygons • …

  4. Why Vector Graphics • Compact • Scalable • Editable • Easy to animate

  5. Compact input raster image 37.5KB optimized gradient mesh 7.7KB

  6. Why Vector Graphics • Compact • Scalable • Editable • Easy to animate

  7. Scalable original image vector form bicubic interpolation

  8. Why Vector Graphics • Compact • Scalable • Editable • Easy to animate

  9. Editable

  10. Why Vector Graphics • Compact • Scalable • Editable • Easy to animate

  11. Easy to animate

  12. Related Work • Cartoon drawing vectorization • skeletonization, tracing and approximation • Triangulation-based Method • Object-based Vectorization • Bezier patch • subdivision

  13. Image Vectorization using Optimized Gradient Meshes Jian Sun, Lin Liang, Fang Wen, Heung-Yeung Shum Siggraph 2007

  14. About the author --- Jian Sun • Lead Researcher, Visual Computing Group, Microsoft Research Asia • Research interests in • stereo matching • interactive computer vision • computational photography

  15. Surface Representation • A tensor product patch is defined as • Bezier bicubic, rational biquadratic, B-splines… • control points lying outside the surface

  16. Ferguson Patch

  17. Gradient Mesh • Control Point Attributes: • 2D position • geometry derivatives • RGB color • color derivatives

  18. Flow Chart Original Initial Mesh Optimized Mesh Final Rendering

  19. Mesh Initialization

  20. Mesh Initialization • Decompose image into sub-objects • Divide the boundary into four segments • Fitting segments by cubic Bezier splines • Refine the mesh-lines • evenly distributed • interactive placement

  21. Mesh Optimization input image final rendering initial rendering

  22. Mesh Optimization • To minimize the energy function P: number of patches

  23. Levenberg-Marquardt algorithm • Most widely used algorithm for Nonlinear Least Squares Minimization. • First proposed by Levenberg, then improved by Marquardt • A blend of Gradient descent and Gauss-Newton iteration

  24. Smoothness

  25. Smoothness Constraint • Add a smoothness term into the energy which minimizes the second-order finite difference.

  26. Vector line guided optimized gradient mesh

  27. Vector line guided optimized gradient mesh • Given vector fields Vu and Vv, we optimize

  28. More Results

  29. More Results

  30. THE END. Thank you!

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