Project #1: Images of the Russian Empire

Annie Xie

Project Overview

In the 1900s, Russian photographer Sergei Mikhailovich Prokudin-Gorskii recorded three exposures of every scene onto a glass plate using a red filter, green filter, and blue filter as a way to create color photographs. The idea was to align the three stills to produce a color image, but unfortunately, he never saw his plans come to fruition. The goal of this project is to take the digitized glass plate images and automatically align them to create the color images from the Russian Empire!

For the smaller images, I performed a search over possible x-displacements and possible y-displacements in the range of [-15, 15] to find the best alignment between two channels. I used sum of squared differences to measure how good an alignment is and found the x-, y-displacement that maximized the sum of squared differences. To minimize the effect of the edges on the calculations, I cropped out 10% of the channel images before calculating the SSD. To create the final image, I aligned the red and green channels to the blue and stacked them on top of each other.

To use the naive algorithm on the larger images, we would need to search for the optimal displacement in a much larger range, making the algorithm extremely slow. Thus, we extend the simple algorithm to search through a pyramid of the original image at various scales. I scale the image down by a factor of 2 until the height is smaller than 400 pixels and search through the scaled down version with the same [-15, 15] range for the optimal x-, y-displacement. Then, scale it back up by a factor of 2. In the new image, I find the new best displacement again in the range of [-15, 15] offset by 2 times the optimal x-, y-displacement found in the previous step. This is repeated until we have scaled all the way back to the original image and found the best displacement at the original scale.

Results

Cathedral

G: (2, 5) R: (3, 12)

Cathedral

Monastery

G: (2, -3) R: (2, 3)

Monastery

Nativity

G: (1, 3) R: (0, 8)

Nativity

Settlers

G: (0, 7) R: (-1, 15)

Settlers

Emir

G: (24, 49) R: (57, 103)

Emir

Harvesters

G: (16, 59) R: (13, 124)

Harvesters

Icon

G: (17, 41) R: (23, 90)

Icon

Lady

G: (8, 56) R: (11, 116)

Lady

Self Portrait

G: (29, 79) R: (37, 176)

Self Portrait

Three Generations

G: (14, 53) R: (11, 112)

Three Generations

Train

G: (6, 43) R: (32, 87)

Train

Turkmen

G: (21, 56) R: (28, 116)

Turkmen

Village

G: (12, 65) R: (22, 138)

Village

More Images

Resurrection (jpg)

G: (3, 5) R: (4, 11)

Resurrection

Portrait (jpg)

G: (-2, 5) R: (-6, 11)

Portrait

Melons (tif)

G: (11, 82) R: (13, 178)

Melon