1. Stitching Photo Mosaics
IBMR Assignment 1
Stitching Photo Mosaics

2. What is Photo Mosaic? Stitching photos to construct a wild-view scene.
Part1: CORNER DETECTION
Part2: PERSPECTIVE MAPPING and MOSAICING
Handout after Part2 Finished

3. PERSPECTIVE MAPPING and MOSAICING

4. Requirement
Read n>2 images, and create an image mosaic by registering, projective warping, resampling, and compositing them.
(bonus) multiband blending, SIFT ,panorama or other methods mentioned in class.

5. Just overlapping

6. Steps Shoot the Pictures Recover Homographies
Warp the Images/ Image Rectification
Gain Compensation
Blend the images into a mosaic

7. Shoot the Pictures
You may use the photos on the webpage, but shoot your own photos and mosaic them will get bonus credit.
Shoot photos as:
Overlap the fields of view significantly. 40% to 70% overlap is recommended.

8. Recover Homographies
Construct a linear system as: p’=Hp, where p’ and p are correspondence points.
Follow the Lecture 8 page 6~9. You may try Affine mappings(DOF=6) or Projective mappings(DOF=8).
Solve Ax=0

9. Warp the Images/Image Rectification
Source scanning(forward mapping) or destination scanning(inverse mapping).
You will need to avoid aliasing when resampling the image.
Be careful of the size of the resulting image.

10. Gain Compensation
Find the optimize gains of gi according to means of overlapping regions between image pair i and j.

11. Blend the images into a mosaic
Linear blending by the weights:
where w(x) varies linearly from 1 at the centre of the image to 0 at the edge.
Multi-band blending (bonus): A B
𝐼(𝑥,𝑦)= 𝐼𝑎∗ 𝑊−𝐷𝑎 +𝐼𝑏∗(𝑊−𝐷𝑏) 𝑊−𝐷𝑎 +(𝑊−𝐷𝑏)

12. Multi-band blending Band 1 scale 0 to σ Band 2 scale σ to 2σ
Band 3 lower than 2σ

13. Support Your own project1a code. A C called matlab library.
to calculate inverse matrix , SVD or etc.

14. Result

15. Grading Basic: 75% Bonus: Harris Corner Detection + KNN (Hw1a) RANSAC
Projection Mapping / Affine Mapping
Image Warping
Bonus:
Non-Maximum Suppression 5%
KD Tree 5%
SIFT 15%
Gain Compensation 10%
Linear Blending 5%
Multi Blending 10%
Stitching your own photos 5%
Others

16. Deadline 11/22 11:59:59pm Upload your program & report to:
host : caig.cs.nctu.edu.tw
port : 30021
username : IBMR10
password : IBMR10
and create your own folder with your ID.