Computational Photography Assignment 1

Alyssa Reuter - Spring 2010

Description

To align the color channels, I implemented a modified approach to the Sum of Squared Differences (SSD) distance (which compares edges instead of values), as well as an image pyramid for the larger images. Furthermore, I only consider the center 25% of the image during matching, which reduces error by ignoring the inaccuracies near the edges. When the algorithm is finished, it prints out the required displacements for the red and green channels in matlab's command window.

The algorithm automatically crops off the boarder to eliminate most of the ugly colors at the edges. There are a few cases where there are still some remnants of color, but I did not want to crop down too far and risk losing information in the majority of images which looked okay.

Outcome

I had very good results for all the required images, which can be viewed here. My biggest concern is that the large TIF files take 2 or 3 minutes to process, but maybe this is to be expected. There was only one image that did not turn out quite as well:

The reason for this error is that in my algorithm I only look for displacement possibilities within a [-15,15] window, but the required offset for this particular image is beyond that (it requires a [-25,25] window). I'm hesitant to change my algorithm since it will make the large images even longer to process, but I did run the adjusted algorithm on the image to show the results: