Images of the Russian Empire: Colorizing the Prokudin-Gorskii photo collection

All images worked with were from the early 1900's Prokudin-Gorski photo collection and can be downloaded here These photos are glass plate images involving taking three pictures with diffrent filters for each color channel (red, green, blue).

The crux of this is to use image processing techniques such as image pyramids and exhaustive search, to overlay the glass plate images atop each other to form a single RGB color image. All images processed can be found below.

The algorithm for larger images is as follows. Successive rescaling was done by a factor of .7 each time until the image was 500x500 pixels or smaller, then from here a large window was sampled to find the best displacement. Going back down the pyramid (towards higher resolutions) to successively get closer to the optimal displacement was then done for both the red and green channels before finally overlaying them atop each other for the final images.

Cropping the images before finding the displacements greatly improved results and reduced noise when computing L2 norms, however this caused more exaggerated the colored lines on the edges of the photos. Although they could be cropped out they look more interesting like this and it was kept.