A well-known result from linear algebra is that one can use a matrix to represent any linear mapping between two vector spaces. While rotation is a linear mapping, translation unfortunately is not. But, wait… by adding another dimension to the vector space, and by interpreting the vector coordinates correctly, we are able to perform rotation and translation with a single matrix multiplication! This article describes how to restore a fragmented image with the help of homogeneous coordinates.

Motion blur usually occurs in an image, when the camera was moved with respect to the subject. Motion blur has an interesting effect on the Fourier-transformed image, as pointed out by D. Burschka at University of Technology, Munich. Here is an example how the Fourier-transformed images of toy images look like that have been subject to motion blur.

When using Gnome 3, one can access the dashboard by moving the cursor to the top-left corner of the screen. As it turns out, I always kept accidentally moving the cursor to this “hot corner”, thereby opening the dashboard involuntarily. Here is a small hack that disables this hot-corner effect. You are still able to show the dashboard by activating the “super” key.

Encrypting your hard drive is generally a good idea. Yet, the encryption renders dual-booting a little more difficult. Here I briefly sketch how I installed Ubuntu in parallel to an existing Arch installation on a LUKS-encrypted drive.

Being suprised by a low-flying unidentified objects? Maybe it was just a remote-controlled airplane by Team Black Sheep, who were giving a talk at TNG Big Techday in Munich on 2011-05-27.

Having a poisson-distributed random variable X, how can we efficiently generate samples (or say realizations) of that random variable? This article shows how Knuth’s technique can be derived and it also indicates that the Ratio-of-Uniforms method is quite efficient.

This article shows the derivation of an algorithm for resizing images in Matlab, using nearest-neighbor interpolation. Scaling an image is mathematically just multiplying image coordinates by a scaling factor. Surprisingly, when dealing with digital images, the scaling process becomes a little bit more complex.

Über wenige Webhosts lassen sich beliebige Top-Level-Domains registrieren. Beispielsweise ist es derzeit (Juni 2010) bei Dreamhost nicht möglich, de-Domains zu bestellen. Bei deutschen Anbietern wiederum ist dies möglich, im Niedrigpreissektor z.B. bei Evanzo. Bei Evanzo hat man Zugriff auf die DNS-Einträge der Domäne.

Keine besonders umwerfende Erkenntnis, aber diese Identität hat mir letztens weitergeholfen:

Wozu dient der DBus? Und wie spricht man ihn an? Ein einfaches Beispiel in fünf verschiedenen Sprachen —- mit Java, OCaml, Python, C und der Shell!

Feldversuch. Wie funktioniert Cairo in Verbindung mit OCaml?

This article briefly introduces some existing programming concepts. It is a summary of a couple of interesting approaches that were presented at Ferienakademie 2009.

PostScript ist eine Programmiersprache, die zur Beschreibung von Seiten dient. Mit ihr programmiert man direkt auf dem Stack und nutzt dabei die umgekehrte polnische Notation, was einigen Spaß bereitet, sobald man mal den Dreh herausgefunden hat. Mit PostScript kann man programmatisch skalierbare Grafiken zeichnen.