Sunday, 30 October 2016

A punched card reader in javascript

While trying out the Ektoparty CTF 2016 there was a challenge which requires to decode a series of punched card images. A punched card looks like this

A Punched Card
Fig 1: A sample punch card

The small white blocks denote the punch. All of the card images were specifically generated by an online service - Card punch. However, on searching for a tool which reads such images, I found nothing, hence I developed a small web app which can read in these punched card images. Please do note the card image must have an exact dimensions of 588 x 264 or else the tool wont work. You can try out the tool here or below. The source is on github.


  1. followed instruction to convert image to 588x264 loaded image but
    did not convert?

    1. At that time the images had a dimension of 588x264. It may have changed meanwhile. As a result even after resizing the image the punches won't be in the exact same position as was earlier.