Project 1: Hybrid Images

Background

For this assignment, I've implemented an grayscale-only implementation of hybrid images as introduced by the 2006 paper by Oliva, Torralba, and Schyns. At close distances, viewers perceive only the high frequencies of an image. Only after moving far away from the image do the low frequencies begin to stand out. Hybrid images leverage this aspect of perception by merging the low frequencies of one image and the high frequencies of another into a single static image. As a result, one image is seen at close distances while the other starts to appear as the viewer moves further from the screen.

Hybrid images are constructed by taking the Laplacian pyramids of two images. Instead of reconstructing an image using one image's pyramid, the lower levels of one image (like Her Majesty Queen Elizabeth II) are used to contribute the lower frequencies of the image and the higher levels are used from the other (like His Majesty Big Bird) for higher frequencies.

Results

Aside from the images provided with the stencil code, I used pictures of Muppets and their celebrity impersonators. In some cases, it made for good results (e.g. Big Bird and the Queen), while in other instances the subjects looked too much alike for either image to stand out at any distance (e.g. Al Roker and Professor Bunsen Honeydew). Smaller versions of the results are included to simulate viewing the images from a distance.

I found that there wasn't any benefit to fiddling with the cutoff-frequency for any of the images. Each result is formed by compositing the bottom 5 levels of the lower frequency image's Laplacian pyramid with the top 3 levels of the higher frequency image's pyramid.

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