This is part one of a tutorial that describes how to create a reconstruction of a cone-beam computed tomography (CT) dataset. This tutorial includes the preprocessing step that is needed to go from raw X-ray images to projections that…
2020 was a really quiet year on this blog, with a grand total of four articles posted… I’ve been working full-time (and sometimes a bit more) in my consulting business, and the time to write blog posts often eluded me. Instead of going over the…
A Voronoi diagram is a partition of the plane into a number of cells, where each cell consists of exactly those points that are closest to the site (or seed point) of that cell. An example with ten seed points is shown in…
When you are designing a modem, you’ll typically make heavy use of simulations. Much of the design work is concentrated on the algorithmic part of the device, especially in these days of Software-Defined Radio (SDR), where the actual electronics might…
Now that we are just past Pi Approximation Day (22/7 or July 22), I thought about how to find other fractional approximations of pi with small numerators and denominators. I decided that I was going to brute force this thing, just because I can…
A year is the time that it takes the Earth to complete one revolution around the Sun. You might think that a day is the time that it takes the Earth to complete one rotation of 360 degrees, but that isn’t true. A full 360 degrees rotation takes only about…
This article is a wrap-up of what happened on TomRoelandts.com in 2019.
There is really only one circle. Of course, you have to allow for translation and scaling for this to be true, but I think you’ll agree that a large circle is essentially the same as a small one. The geometrical term for this is similarity. Two objects are similar if…
In the context of images, steganography is the hiding of an image (or other information) within another image. The “carrier image” can then be sent over an untrusted channel (e.g., published on the Internet), and only people that know that the hidden message is there will…
With fractional delay, I mean a delay of a fraction of a sampling period. Introducing a delay of an integer number of samples is easy, since you can do that by simply skipping a number of samples, or buffering them if you don’t want to…