Tracking an object over a sequence of 2D images is a challenging task. One approach uses a linear mapping between observed intensity differences and target motion; this is presented in the paper Hyperplane Approximation for Template Matching by F, Jurie and M. Dhome. Here are some results from an implementation in Matlab by a fellow student and me.
Your wireless presenter is not working for prezi.com in full-screen mode? Here is how you might be able to fix the issue on X-based Linux desktops by temporarily remapping the “Page Up” and “Page Down” buttons of your keyboard.
A set of images that have some common overlapping regions can be stichted together to form a panorama picture. Some recent camera models can even compute the panorama picture internally and do not require post-processing on the computer. While this is a problem that has already been solved (for example, there is AutoStitch, here are some hints on classic DIY-panorama-stitching using Matlab, SIFT, DLT and RANSAC.
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.
Who has the luxury of working on a green field project where you can write everything from scratch, and thus feel in control about your code? I usually don’t. There are several good reasons that force programmers to develop their skills in reading code they have not written by themselves. You might want to add a feature (extending existing code), fix a bug (maintaining existing code), look for inspiration (learning from existing code) or integrate functions into another project (reusing existing code). All of these goals require you to read code.
Unsharp masking is an image enhancement technique that sharpens an image and highlights fine detail and put more weight on edges. By subtracting a blurred version of the original image, one obtains an unsharp mask that in turn can be added to the original image. An easy-to-digest explanation can be found in the “GIMP help pages”:file:///usr/share/gimp/2.0/help/en/plug-in-unsharp-mask.html. Here is an example of a picture before and after unsharp masking:
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.
Besonders nett und nicht nur zum Entwerfen von Tapetenmustern hilfreich. Wolfram|Alpha zeichnet Bereiche im R^2. Beispiel:
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:
$${n \choose a} {n-a \choose b} = {n \choose b} {n-b \choose a}$$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!
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.