Skip to main content helps meld the past and the present by creating then-and-now pictures
Image used with permission by copyright holder
You’ve probably seen them all over the web — those then-and-now pictures with a slider that lets you swap the view between the two. Now, a retired computer engineering professor is working to make those before-and-after comparisons easier to create. The project is based on “rephotography” and the first manifestation of the idea is a website called that will automatically align your than and your now to match up perfectly.

Rephotography is the idea of taking the same exact picture years. and even decades. apart to illustrate the changes over time. Oliver Vornberger, a now-retired professor at the University of Osnabrück in Germany, started the project two years ago and now works with computer science students to continue to add new ideas. The website that aligns then-and-now photos is the first step, and the group is also working on an iOS app that will direct users where to shoot from to get the same angle as the earlier picture. currently works by uploading two different images, a before and after, then setting four different markers that tell the computer which parts of the photos should match up. The computer then aligns the photos based on those points, delivering before and afters that line up despite the changes over the years. The final product is two aligned photos with that slider animation, created through Juxtapose, that allows you to view each photo separately or half of each shot at the same time.

Along with the upcoming app, another student is working on an algorithm to update the website so those four reference points aren’t required and the software can align automatically without that user input.

The software, as it stands, works with both buildings and people — though we also tried it as a before and after for a DIY project. Along with aligning the photos, users can add date and time information and share the images. Users can also browse other before and afters, including aerial views and nature, along with buildings and people. Viewers can also comment and rate the rephotography. The platform doesn’t have the option to download at this time. is free to use after signing up for the platform with a username, email, and password. The new platform already has more than 300 users and over 800 then-and-now compilations to browse through for inspiration or to get a general idea of how the platform works.

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