My Contribution to the Public Domain

Well, here is my humble contribution to the Public Domain, sorted roughly in chronological order. I hope you will find some of the following helpful ...

There is also older stuff, which probably no one is interested any longer in.

Experiments on Approximate Nearest-Neighbor Search using kd-Trees (with Python Code)

In this set of experiments, I wanted to determine under what circumstances and parameters the approximate nearest-neighbor search using a kd-tree is significantly faster (in practice) than the exact nearest neighbor search using a kd-tree. As you know, there is always the curse of dimensionality.

Batch convert all Powerpoint files in a folder to PDF

Here is a Applescript program (zipped) for Mac that will convert all Powerpoint files in a folder to PDF in a batch. (For Google, here it is again as a plain text file.) You need Powerpoint:mac 2011.

Apparently, this should also be possible (and easier) with Automator, but the required Automator actions are not installed on my machine, and many others', too (which seems to fit the common Micro$oft practice, that everything has to be paid and installed extra).

OpenGL Transform Feedback Example

Here is a simlpe, self-contained example program (actually, three) that demonstrates the Transform Feedback of OpenGL. It shows two triangles (or 2x2 points, resp.), the latter of which is a copy of the former that was obtained via the Transform Feedback. I have developed and tested the program under Mac OS X 10.6 using XCode 3.2 with an ATI graphics card. So it should also compile as-is under Linux (you just need Glut).

Since getting the transform feedback to work has caused me considerable headache (I also needed a lot of help), I thought I'd post this TAR file. Hopefully, it will help reduce the headache of others.

Concatenate movies automatically

Here is a little Automator Workflow, with which you can concatenate a number of movies automatically. You first have to open the workflow in Automator. Then you select the movies in Finder. Then you click the "play" button in Automator.

Make your presentations / lectures more lively with PowerDraw

PowerDraw Download - Have you ever wished to just draw a few lines on the screen during your presentation? Or did you wish you could highlight a word or phrase or part of a drawing during your lecture? Maybe you even wanted a few blank slides so you could explain something in more detail?

Then PowerDraw is the tool for you.
It is particularly useful when giving presentations / lectures using a ModBook (this is a tablet MacBook).
On the right you can see a picture how it looks like

Here is an overview of the features:

Installation: just download the disk image and move the application inside to your Applications folder.

Usage: just run PowerDraw, the rest should be straight-forward.

Prerequisites: Mac OS X 10.5 or higher and, if you want to use it with Powerpoint, Powerpoint 2008.

Donation: if you find yourself using this app sometimes, please consider making a donation (see the button at the bottom of the configurations sheet); all kinds of donations will be highly appreciated!

License: please notice that I put PowerDraw under a copyright and license that basically says it's free for personal use but not for commercial use.

Test program showing how to create a window that is always on top, transparent, and still gets mouse events in Cocoa (on Mac OS X)

Because it cost me at least 2 days to find out how to create a window under Cocoa that allows to do the following: I post this little test program ; here is the single source file again, so that (hopefully) people will find it better via google (it is, of course, contained in the zip file, too). It works under XCode 3.1.3 and Mac OS X 10.5 (Tiger).

Make the iPhone work with congstar

When I switched to congstar in Germany, I had the problem that it wouldn't let me enter the parameters for the Cellular Data Network (APN, username, password) although my iPhone did receive an EDGE signal.

I solved this with the following procedure:

  1. Download this Carrier Bundle: and unzip it.
  2. Copy it over to your iPhone:
    scp -r congstar_de.bundle"/System/Library/Carrier\ Bundles",
    where is the current IP address of you iPhone. (I usually do this by creating a private network on my Mac.)
  3. Ssh into your iPhone:
    cd /System/Library/Carrier\ Bundles.
  4. Make the new carrier bundle the one to be used in Germany on the T-Mobile network like so:
    # mv 26201 26201_old
    # mv 26206 26206_old
    # ln -s congstar_de.bundle 26201
    # ln -s congstar_de.bundle 26206
  5. Reboot your iPhone.
And by some magic, I even got the correct internet parameters in Settings -> General -> Network -> Cellular Data Network after the reboot, namely APN = internet.t-mobile , username = t-mobile , password = tm ! (They are not contained in the carrier bundle...)
Update: with the upgrade to firmware 2.2, I don't have the menu 'Settings -> General -> Network -> Cellular Data Network' any more :-( , but the settings are still correct ;-)

The iPhone still doesn't show the carrier's name at the top left (next to the signal strength), and you still get a blank carrier name in Settings -> Carrier, where it should say D1 or T-Mobile ... but, oh well ...

I've got an iPhone 2G with firmware 2.1, jailbroken and unlocked.

I relied on a number of most valuable sources for the above procedure: , , (the plutil was already installed on my Mac).

Batch Convert a Number of Movies with Quicktime

Here is a little applescript that batch converts a number of movies into the format that you have used last time when you converted a movie using Quicktime.
Just unpack the gzip file (double-clicking should do it), then drag a number of movies onto the icon.

A few Basic Shapes as OmniGraffle Stencil

I have imported a few shapes from Visio into OmniGraffle and created a stencil of them. It contains a curly brace, a number of cloud shapes, thunderbolts, block arrows, and callout boxes. Just download the zip file, unpack it, and move the .gstencil file into ~/Library/Application Support/OmniGraffle/Stencils.

Move Off-Screen Windows to the Main Screen

Here is a little applescript that moves all windows that are almost or completely off-screen to a position on the screen (main display).
This can be very handy when you plug in your Mac laptop to different displays (such as projector and flat panel). Then, it often happens (to me, at least) that some windows get pushed to the very sides of the screen, so that only a few pixels of the windows remain on-screen.
I should mention that this version is based on the script provided by Jonathan Laliberte

Here is a little variation; the difference is: all windows that are more or less off-screen (no matter how much) are moved back so that they are completely on screen (if possible).

Counting Polygons in VRML / X3D

If you want to count the number of polygons in a VRML / X3D file without a VRML loader / brwoser, here is a little script.

Simplex Noise

Here is a port to GLUT of Stefan Gustavson's demo of "simplex noise", which was invented by Ken Perlin. My port compiles and runs fine under Mac OS X 10.4 on my Powerbook, and it should also compile fine under Linux (please let me know).


(The following text is in German, because the Excel sheet is in German, too.)
Mit diesem Excel Sheet kann man Klausurergebnisse komfortabel auswerten, d.h., Noten erstellen und kleine Statistiken erzeugen. Hier sind 3 Beispiel-Snapshots: Bsp 1, Bsp 2, Bsp 3 (verschiedene Ausschnitte desselben Excel-Sheets).

Folgende Dinge berechnet das Sheet automatisch:

Alle diese Dinge werden automatisch berechnet, sobald man eine der Eingaben ändert (z.B. Punkte in einer Aufgabe, Schwellwerte, etc.). Folgende Daten muß man eingeben: Eine kurze Anleitung und Erläuterungen sind im Excel-Sheet enthalten.

Bemerkung: Beim Öffnen muß man "enable macros" anklicken (ansonsten funktioniert die Aktualisierung der Farbcodes der Noten nicht; alles andere funktioniert aber weiterhin).

Make Proceedings from many PDFs

This page explains an easy method to produce a single PDF (such as a proceedings) from a bunch of PDFs, such that the pages of the single PDF have headings and consecutive page numbers.

Print Your Mac's IP

This little script prints your external as well as your internal IP on the command line.

These two IPs might be different if you are behind a router or a NAT device. The script is written in Python (which is installed on your Mac).

Find Duplicate Files on the Mac

Here is a little command line tool for Mac OS X (10.4, Tiger) that finds duplicate files in a directory tree. Just put the binary somewhere in your PATH, e.g., ~/bin.

Details: Find files that are (byte-wise) identical, but are (possibly) scattered among different directories. This might happen, for instance, if you copy a large directory tree and (accidentally) resolve symbolic links during the copying.
The output (on stdout) consists of two lists (mainly): first a list of files that have been found to be equal, one file per line, and the last file within each group of equal files gets a period appended; second, the list of duplicates sorted by complete pathname.
Special files, like .DS_Store, are not considered. Also, special directories, like CVS, are skipped. In addition, only regular files are considered, no symbolic links or other special files.
The implementation uses a number of optimization tricks to speed up the search. On my G4, scanning a directory tree consisting of 40,000 files in total, containing 7,000 duplicates, took about 3 minutes.

And here is the source code as XCode 2.4 project.

Photo Screen Saver for the Mac

ArtSaver has a home on its own page, now.

Convert CSV to Mail Aliases

I transfered all my contacts from my good old Revo to a Siemens CX65. But I send my email under Linux using mutt. So here is a little Perl script that converts a CSV file into a file containing an email alias for each name. Prerequisite: the Perl module Text::xSV (see the man page perlmodinstall for installation instruction).

 by ChangeDetection (it's free and it's private).
Gabriel Zachmann
Last modified: Wed Nov 28 22:19:42 MET 2012