In this project, we restored the color of images from the Prokudin-Gorskii collection, a collection of glass plates exposed in 3 colors that records color photographs. In order to do so, we needed to align the 3 filtered channels correctly, as the alignment is slightly off to begin with. For my approach, I used normalized cross-correlation (NCC) as a metric to compare color channels at different offsets, under the (slightly flawed) assumption that the exposures in the 3 channels would be of similar distribution. I implemented image pyramid for the higher resolution TIF images to reduce the number of NCC computations needed to arrive at a precise alignment.
Initially I used the SSD metric to compare images, but NCC proved to be a more accurate metric. Then, I had trouble tuning the parameters of the image pyramid. The optimal depth and crop amount ended up being 4 and 200 respectively; it was also helpful to search more extensively at the deepest level, when the NCC operation is the cheapest.