Tag Archives: Science

Astronomy Calendar of Celestial Events – UPDATED

My Astronomy Calendar of Celestial Events is up-to-dated now. I entered both past and upcoming events from 2011 December 14 until 2012 December 14.
Source: Sea and Sky.


Generating color palettes – based on the Fibonacci sequence

We are continuously facing with complicated mathematical concepts every day, even without knowing about their existence.

Just take a look at the range of IP addresses. In ideal case an IP address tends to be closer to another IP address even when adding some new addresses between, the concept of the Hilbert curve:

The previous theory is highly applicable from machine point of view, but there are also plenty of theories applicable from human point of view. Maybe the most famous is the Golden Ratio or Divine Proportion:

In mathematics and the arts, two quantities are in the golden ratio if the ratio of the sum of the quantities to the larger quantity is equal to the ratio of the larger quantity to the smaller one.

  a    b

meaning, a+b is to a as a is to b. From the machine’s point of view, nothing particularly happens, it’s just a “constant” which values is 1.6180339887… (yes, with quotes, the value of this proportion is an irrational number therefore I’m not sure about using the term “constant” when talking about irrational numbers, if you think otherwise, leave a comment below). However this “constant” is really important when talking about beauty and perfection generally. It appears in everything which is aesthetic to us, humans:

1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, … as you may have already realized, the next number in this sequence should be 55+89=144. The numbers of the Fibonacci sequence, or the Fibonacci numbers. What could be so interesting in this sequence other than describing the growth of an idealized rabbit population?
If you don’t know yet, let me show you. Divide the current and the previous number of the Fibonacci sequence above, starting from the second element, repeating infinite times:

\frac{1}{1} =1\newline\newline \frac{2}{1}=2\newline\newline \frac{3}{2}=1.5\newline\newline \frac{5}{3}=1.66..\newline\newline \frac{8}{5}=1.6\newline\newline \frac{13}{8}=1.625\newline\newline \frac{21}{13}=1.615\newline\newline \frac{34}{21}=1.61904...

As you may have already discovered the results of these iterations are approaching to the value of the Golden Ratio (see above, it was: 1.6180339887…).

The question is appropriate: Is there any way to apply this abstract representation of the golden ration?

Let’s take a look at the hexadecimal representation of a color “from the web”, a0ff11. Each color consist of three components, the red: a0, the green: ff and the blue component: 11. The idea is very simple: increment every component by the elements of the Fibonacci sequence.

The implementation happened in JSP, because everyone needs to know JSP!!1 currently I’m advancing in JSP. 🙂
Nothing fancy just a simple opening page to gather the required parameters, like the base color, number of color in the palette and the component which have to be modified:

<title>Color Palette Generator</title>
	<form action="generator.jsp" method="get">
				<td>Base color:</td><td><input name="baseColor" type="text" /></td>
				<td>Palette size:</td><td><input name="sequence" type="number" /></td>
			<tr valign=top>
				<td>Component to modify:</td><td>
				<input type="checkbox" name="red" value="r" />Red
				<input type="checkbox" name="green" value="g" />Green
				<input type="checkbox" name="blue" value="b" />Blue
				<input type="submit" value="Generate" />

modifying only by blue component

click to enlarge

Now some green magic:

click to enlarge

…and some red:

click to enlarge

And finally some of the colors I picked up randomly, all three modified components are rendered at once:





The code itself is quite simple.

<%@ page language="java" import="java.awt.Color,java.util.*"%>
<%!/* Some members of the mighty Fibonacci sequence
	 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987
	// and some of them what I found useful:

	int fib[] = { 13, 21, 34, 55, 89, 144 };

	//int fib[] = new int[] { 2, 3, 5, 8, 13, 21, 34 };
	//int fib[] = new int[] { 5, 8, 13, 21, 34, 55, 89 };

	public ArrayList generatePalette(Color baseColor, int n, String modifier) {
		ArrayList<Color> colorVector = new ArrayList<Color>();
		Color tmp = baseColor;
		for (int i = 0; i < n; i++) {
			tmp = generateColor(tmp, fib[i % 6], modifier);
		return colorVector;

	public Color generateColor(Color color, int delta, String modifier) {
		int r = -1;
		int g = -1;
		int b = -1;

		if (modifier.equals("r")) {
			r = add(color.getRed(), delta);
			g = color.getGreen();
			b = color.getBlue();
		} else if (modifier.equals("g")) {
			r = color.getRed();
			g = add(color.getGreen(), delta);
			b = color.getBlue();
		} else if (modifier.equals("b")) {
			r = color.getRed();
			g = color.getGreen();
			b = add(color.getBlue(), delta);

		return new Color(r, g, b);

	public String colorToStr(Color color) {
		String r = Integer.toHexString(color.getRed());
		String g = Integer.toHexString(color.getGreen());
		String b = Integer.toHexString(color.getBlue());
		r = r.length() < 2 ? "0" + r : r;
		g = g.length() < 2 ? "0" + g : g;
		b = b.length() < 2 ? "0" + b : b;
		return r + g + b;

	// if > 255 restart from 0
	public int add(int old, int d) {
		if (old + d > 255)
			return old + d - 255;
			return old + d;
	String baseColor = (String) request.getParameter("baseColor");
	int colorToInt = Integer.parseInt(baseColor, 16);
	Color newColor = new Color(colorToInt);
	String sequence = (String) request.getParameter("sequence");
	int times = Integer.parseInt(sequence);
	String[] modifiers = new String[3];
	modifiers[0] = (String) request.getParameter("red");
	modifiers[1] = (String) request.getParameter("green");
	modifiers[2] = (String) request.getParameter("blue");
<title>Color Sequence Generator</title>
<link rel=stylesheet type="text/css" href="generator.css">
		for (int j = 0; j < modifiers.length; j++) {
			if (modifiers[j] == null)
	<table class="main">
				ArrayList palette = generatePalette(newColor, times,
					for (int i = 0; i < palette.size(); i++) {
						String current = colorToStr((Color) palette.get(i));
			<td class="colorDiv" bgcolor="#<%=current%>"><font

Getting started with Unit Testing

In this post I’ll talk about the concepts and theory of Unit Testing, shortly after the way to implement them. If you were thinking that the “algebra and such as” isn’t part of the practical programming then you were wrong! In this field the set of keyword contains only 1 important element – assert – which either generates an exception or not. Or, more precisely: you have a Groupoid defined on YourClass with (YourClass, assert).
…search engines and tutorials are not the key elements of this game, you will rather use your natural logic. 😉

So, what is Unit Testing about? I could paste here some Wikipedia definition, and after reading it you could ask yourself: why to test some parts of my program once it’s debugged and works correctly.

Imagine the following situation: you have an open-source project – because you are cool -. It’s source code is quite big, consists from 100 unique classes and 1000 definitions and holds 10000 lines of code. As I said, its open source, what means today you’ll hack something on the getFeedProperties() item, tomorrow I’ll and after a week a third person.

After a month when you are starting to package your software you discover that something is wrong with the program. It’s working, but in a little different way. Actually it’s showing the Feed’s URL instead of their desired name (yeah, it’s probably a feed reader).

What will you do? Of course debug it! You assume that the bug appears in the nth class. After checking the formatting parameters, the string output, etc. you discover that everything is fine in this class. No problem, backtrack it, look at the n-1th class and increment you personal wastedTime variable with 1 :P. Unfortunately in the n-1th everything is okay, so wastedTime++, take a look to n-2th class. After k steps you will reach the last class in your debugging, and you will found out that the getFeedProperties() returns the desired object, but the object’s name field is set to the feed’s URL.
Conclusion: problem solved with time requirement of O(n-k), it’s linear, not bad!
Could be it better?

What happens if your project has built with Unit Testing? When a third person submits his own patch for something what breaks something else, your automated Unit Test will report if some method is working different then it’s expected. So, if I should define: Unit Testing is about defining the behavior of different parts in your program between the given circumstances.

Take a look to this pseudo code:

// from the feed reader messed up by a 3rd person
FeedProperty getFeedProperties() {
// from FeedReaderTest test class
Feed f = new Feed("http://planet.ubuntu.com/rss20.xml", ....);

void testGetFeedProperties() {
FeedProperty fp = f.getFeedProperties();
assert fp.getFeedName == "Ubuntu"
//an exception will be generated here, because the getFeedProperties placed wrong string into the "name" field of your "f" object. Your class is inconsistent. The bug is obviously here.

Time requirement: O(1), the bug were found by running the top of your Unit Testing class.

Any thoughts, comments, spams are welcome!

Researchers’ Night 2010, Novi Sad – Serbia

In this year, together with other 32 European countries Serbia represented itself too on the Researchers’ Night at Novi Sad.
It was totally awesome to see those experiments from YouTube, live! in front of you with a bunch of technical innovation.

For example, I was totally impressed with the brain-wave controlled software. Imagine a complete software environment for controlling your Facebook account – writing statuses, “like-ing”, commenting, approving friend requests – without using the “standard” input hardware.

Have you seen this before?

I already tried it! Actually I was totally n00b and the “coolest” thing what I’ve managed to do with this touchdesk was dragging the figures… This technology was implemented – in the form of education software – by the guys from FIT. Basically: put the special eye-glasses (it was assembled by them too) and start to draw something with the touchpad. I drew a circle-like figure, after a few sec it’s loaded everything what was stored in the softwares database and was similar to a circle. You can drop any item from the list of similar figures to the workspace and interact with them like in the video above.

Thank to my university a one hour long video conference established with CERN.

Ruben’s Tube + Guitar, experiments and other sexy thing with liquid nitrogen. Robots in any size, solar-powered, competing, industrial…

Here are some photos from their Facebook group, it’s open:

What to say, it was the biggest party of this year so far.

Astronomy Calendar of Celestial Events – from 2010, August

I’ve just made up a simple Astronomy Calendar containing the celestial events from 2010, August according to www.seasky.org.
It is a Google Calendar so you can simply add it by ID: nhsv6ru3irspm1305gthlmf938@group.calendar.google.com
in your Google Calendar on the left side, bottom hit Add > Add a friend’s calendar, paste the ID here.
You can view it as HTML here: http://www.google.com/calendar/embed?src=nhsv6ru3irspm1305gthlmf938%40group.calendar.google.com&ctz=Europe/Prague.
I’ll keep this calendar up-to-date so if you want to embed it just drop me an email.