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parc – projector aspect ratio correction

This is a small piece of JavaScript code that allows you to adjust the scale and translation of your HTML page, in cases where it's being projected in an incorrect aspect ratio.

Have you ever been stuck using a projector that just didn't get the aspect ratio right? I have, and was extremely annoyed by it. As a response I created this project, which simply uses the transform CSS property to adjust your HTML page.

Note: this utility was written to work with a non-scrolling single page, so any page that has scrollbars is going to do some weird layout stuff if you try to scale it. You can also try setting the CSS overflow of your <body> to hidden, to prevent scrollbars from showing up.

Try it now

This page includes the parc.js file from the GitHub repo, so you can try it now to see if it works in your current browser window. Hit the V key to pop up a reference square, and then use the arrow keys to adjust the scale. When you're done, hit the V key again to hide the square.


This library is provided as is, and has been written to work with a pretty narrow use case. So it's highly likely that something may go wrong if you try to use this code elsewhere. See the GitHub site for this project if you want to submit a pull request.


James Allenspach. See the GitHub site for contact info.