Stitching Photo Mosaics IBMR Assignment 1 Stitching Photo Mosaics

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

PERSPECTIVE MAPPING and MOSAICING

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.

Just overlapping

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

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.

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

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.

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

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)

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

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

Result

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

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.