1. Real-Time Image Mosaicing
--Research Project for , Nov 29, 1999
Li Zhang

2. Image Mosaicing
Stitching together images taken from different viewpoints seamlessly
Representation: cylindrical, spherical, and perspective panoramas

3. Problem Statement
Given two images I0 and I1 of a scene, find a transform T that minimizes

4. T is a planar perspective transform M
Special cases
If the scene is planar, and I0 and I1 are taken from different viewpoints with different orientation,
If the scene is arbitrary, and I0 and I1 are taken from same viewpoint with different orientation,
T is a planar perspective transform M

5. My work
Given two images I0 and I1 of a scene, find a transform M that minimizes
Search M interactively in real-time

6. Illustration

7. Algorithm Details(1)
Given I0, I1 and current M, we iteratively update M using
We wish D to minimize

8. Algorithm Details(2) We warp I1 into I1’ such that
We instead wish D to minimize

9. Acceleration Details(1)
We find d by solving a least-square minimization problem with following acceleration techniques:
Approximate the Jacobian as

10. Acceleration Details(2)
Warp I1’ from I1 using hardware-accelerated texture mapping;
Perform minimization hierarchically using OpenGL Mipmaps.

11. Results(1)
Real images of University Center Mural

12. Results(2)
Full view panorama of UC Mural

13. Summary(1) Good features:
Users can interactively create image mosaics in real-time
The transform is locally optimized

14. Summary(2) 8-parameter transform sometimes get stuck in local minimum
The size of image is limited by frame buffer

15. Reference
R. Szeliski and H.-Y. Shum. Creating full view panoramic image mosaics and texture-mapped models. Computer Graphics (SIGGRAPH'97), pages , August 1997.