Real-Time Gradient-Domain Painting

1. ACM-ToG 2008 Real-Time Gradient-Domain Painting James McCann, Nancy S. Pollard Presenter : Min Jung Kim

2. Why Gradient Domain? • Human visual system • Very sensitive to Gradient • Rather than intensity itself • Itseems reasonable as an input • One may wish to work directly in the gradient domain • But it took some time.. Direct cloning Clone gradient : seamless cloning

3. They did it! • Present image editing program • allows artists to paint in the gradient domain • with real time feedback • On megapixel-sized images

4. Application #1 • Drawing & coloring nice picture!

5. Application #2 • Extending the crack using a segment of existing crack • Adding own orange stripe

6. Application #3 • Removing wrinkles

7. In Real Time! An so on …

8. Whole System • Brushes • Allow user to draw gradients • Blending Modes • New gradients are combined with the existing gradients by this mode • Integrator • Allows us to display the result of this process in real time

9. Brushes • Type • Gradient Brush • Edge Brush • Clone Brush • Gradient Brush • Paints intensity difference Original image +strokes Produced gradients Final image

10. Brushes • Type • Gradient Brush • Edge Brush • Clone Brush • Edge Brush • Playback captured gradients(A) Original image +strokes Produced gradients Final image

11. Brushes Original image +strokes Produced gradients Final image • Type • Gradient Brush • Edge Brush • Clone Brush • Clone Brush • Copies gradients relative to a source location(A) onto a destination(B)

12. Blending Modes • Type • Additive Blending • Maximum Blending • Minimum Blending • Over Blending • Directional Blending • Additive Blending

13. Blending Modes • Type • Additive Blending • Maximum Blending • Minimum Blending • Over Blending • Directional Blending • Maximum Blending • Useful when cloning or copying edge Edge brush + Maximum blending mode

14. Blending Modes • Type • Additive Blending • Maximum Blending • Minimum Blending • Over Blending • Directional Blending • Minimum Blending • Useful when cloning or copying edge Edge brush + Minimum blending mode

15. Blending Modes • Type • Additive Blending • Maximum Blending • Minimum Blending • Over Blending • Directional Blending • Over Blending • Useful when cloning or erasing texture with the gradient brush

16. Blending Modes • Type • Additive Blending • Maximum Blending • Minimum Blending • Over Blending • Directional Blending • Directional Blending • Enhances background gradients • Point in the same direction as the brush gradient Shadow was darkened using directional blending

17. Integration • Multi-grid method • The solution for a coarse grid • Resembles the solution for a fine grid • Takes fewer steps to obtain • Can prime the solution for a fine grid

18. Integration • Multi-grid method • Convergence rate • This method turns out to have the fastest convergence Fine grid Coarse grid The large-scale, low-resolution features are solved quickly The small-scale, high-resolution features are filled in on the fine grids

19. Integration single call to V-cycle • Notation • u : image with gradient close • : gradient field of 257x257 image • R : restriction operator • Smooth / subsample • P : interpolation operator • Inserts values / bilinear interpolation What we want What we got : poisson eq. Restrict f to coarser grid 0

20. Integration single call to V-cycle single call to V-cycle Initial condition result of 1 V-cycle result of 1 V-cycle Interpolate, refine the coarser solution Restrict f to coarser grid 0

21. Summary • Demonstrated • easy-to-implement real-time integration system • Interface with different brush types and blending modes • Painting in the gradient domain • Gives users the ability to create and modify edges without specifying an associated region

22. My own example

23. My own example

25. Any Questions?