Project 6: [Auto]Stitching Photo Mosaics

15-463 (15-862): Computational Photography
Project 6: [Auto]Stitching Photo Mosaics

Jun-Yan Zhu

Part 1: IMAGE WARPING and MOSAICING

Overview

In the first part, I implemented the image warping and mosaicing algorithm. There are several steps to achieve the goal. In Shoot the Pictures step, I took some pictures from the second floor of Smith Hall, and used some outdoor images. In Recover Homographies step, I applied the leaset square methods to estimate homography matrix from manually labelled points. (See computeH.m function). In Warp the Images step, I warped several images into a new projection (See imageWarp.m function and generateP.m function). In the Image Blending part, I used distance transform to generate alpha maps and performed alpha matthing (See imageWarp.m functoin and blendIm.m function). After all the above steps, my algorithm could obtain good image mosaic results. The entry point to MATLAB code is stitch.m script. Please set the parameters in setConfig.m function.

Results

The following images are warping and mosaicing results:

EDSH 1

EDSH 2

Outdoor

Part 2: FEATURE MATCHING for AUTOSTITCHING

Overview

In the second part, I implemented feature matching for automatic photo stitching. The project includes several components. First, I used Harris Interest Point Detector to detect corners in a fixed scale. Then, I implemented Adaptive Non-Maximal Suppression to give a better spatial distribution of features. Next, I extracted feature descriptors (i.e. axis-aligned 8x8 patches) around interest points and also blas/gain-normalized the descriptors. Then I performed feature matching. The matching threshold is based on the ratio between the first and the second nearest neighbors. Finally, I applied 4-piont RANSAC to estimate the homography robustly.

Results

The following images are automatic photo stitching results:

Results

The following images are warping and mosaicing results:

EDSH 1

Original Images

Interest Points

Threshold Matching

RANSAC Results

Manual Stitching Results

Automatic Stitching Results

EDSH 2

Original Images

Interest Points

Threshold Matching

RANSAC Results

Manual Stitching Results

Automatic Stitching Results

Outdoor

Original Images

Interest Points

Threshold Matching

RANSAC Results

Manual Stitching Results

Automatic Stitching Results