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2- D IMAGE MORPHING

2- D IMAGE MORPHING. What is image morphing?. Creating a smooth transition between two images 3D model based or Image based Used for obtaining special effects. Use of morphing in movies. Hair-raising Wolfman Dr. Jekyll to Mr. Hyde Michael Jackson – Black & White video.

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2- D IMAGE MORPHING

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  1. 2-D IMAGE MORPHING

  2. What is image morphing? • Creating a smooth transition between two images • 3D model based or Image based • Used for obtaining special effects

  3. Use of morphing in movies • Hair-raising Wolfman • Dr. Jekyll to Mr. Hyde • Michael Jackson – Black & White video

  4. Techniques for image morphing • Cross-dissolve • Field morphing • Mesh morphing

  5. Cross-Dissolve • Pixel-by-pixel color interpolation • Very primitive • Not smooth transitions

  6. Field Morphing • “Which pixel coordinate in the source image do we sample for each pixel in destination image?” • Correspondence achieved using feature line(s) in source and destination images

  7. Field Morphing - Transformation with One Pair of Lines • Corresponding lines define mapping between pixels X and X’

  8. Transformation with One Pair of Lines • For each pixel X in the destination image • Find the corresponding u, v • Find the X’ in the source image for that u, v • destinationImage(X) = sourceImage(X’)

  9. Transformation with One Pair of Lines • Original image (UL), rotated image (UR), translated image(LL), scaled image (LR)

  10. Transformation with Multiple Pairs of Lines • Weighted average of single pair version • a – smoothness of warping • b – falloff of strength with distance • p – rewarding longer lines

  11. Transformation with Multiple Pairs of Lines • For each pixel X in destination • DSUM=(0,0) • weightsum=0 • For each line Pi Qi • Calculate u,v based on Pi Qi • Calculate X’I based on u,v and Pi’ Qi’ • Calculate displacement Di=Xi’-X • Calculate weight • DSUM+=Di*weight; weightsum+=weight • X’ = X+ DSUM/weightsum • destinationImage(X) = SourceImage(X’)

  12. Transformation with Multiple Pairs of Lines • “Lines” are actually line segments • Distance from a pixel to a line is • abs(v) if 0<u<1 • Distance from P if u<0 • Distance from Q if u>0

  13. Transformation with Multiple Pairs of Lines • Not possible to do uniform scaling or shear

  14. Advantages Expressive Adding control points is easy Disadvantages All line segments need to be referenced for each pixel Line segments have global impact Transformation with Multiple Pairs of Lines

  15. Mesh Warping • Source and target images are meshed • The meshes for both images are interpolated • The intermediate images are cross-dissolved

  16. Mesh Warping • for each frame f do • Linearly interpolate mesh M, between Ms and Mt • warp Images to I1, using meshes Ms and M • warp Imaget to I2, using meshes Mt and M • Linearly interpolate image I1 and I2 • end

  17. Mesh Warping

  18. Mesh Warping • Hard to fit the mesh in images • All control points affect the warping equally • Not enough control in certain areas when needed

  19. Transition Control – Uniform Metamorphosis

  20. Transition Control – Non-uniform Metamorphosis

  21. Polymorph

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