Month: February 2010

Getting To Know Eu…ler

Posted by – February 26, 2010

One of the best ways to get to know a programmer is to see their code. You might not know their favorite hobbies, favorite foods, or favorite football team (trick question, programmers don’t like football. Hehe), but getting a glimpse at how someone goes about solving problems can really be quite helpful.

With that in mind, I’m going to be taking part in ProjectEuler.net. It’s all math-based to one degree or another. I am horrible at math, really. I know enough to get by, but a lot of it I’ve forgotten since being out of school. But, I must admit, I love a figuring out puzzles — especially by programming — so I’m anxious to get started.

If you’d like to follow along, feel free to set up an account on their site and try the stuff out yourself. It can get quite addictive :)

Since I’m going to post code-samples here, I might as well include one of my “helper” routines I ended up using in a couple of solutions. Since a few of the problems involved prime numbers, I made a generic function for allowing me to determine whether a specific number is a prime or not.

I’m sure there are more effective ways of figuring out if a number is a prime, but math was never a subject a particularly excelled at…

Function IsPrime(ByVal tmpVal As Long) As Boolean
Dim strVal As String = tmpVal.ToString

'If the number ends in 0,2,4,5,6,8 then it's NOT prime (might be a composite)
If strVal.Length > 1 AndAlso strVal.Substring(strVal.Length - 1, 1) = "0" Then Return False
If strVal.Length > 1 AndAlso strVal.Substring(strVal.Length - 1, 1) = "2" Then Return False
If strVal.Length > 1 AndAlso strVal.Substring(strVal.Length - 1, 1) = "4" Then Return False
If strVal.Length > 1 AndAlso strVal.Substring(strVal.Length - 1, 1) = "5" Then Return False
If strVal.Length > 1 AndAlso strVal.Substring(strVal.Length - 1, 1) = "6" Then Return False
If strVal.Length > 1 AndAlso strVal.Substring(strVal.Length - 1, 1) = "8" Then Return False

'Except for the number 2, if a number is even, it's always composite
If tmpVal <> 2 AndAlso tmpVal Mod 2 = 0 Then Return False

'If a number's digits add up to a number which is divisible by 3, it's composite
Dim tmpDigitSum As Integer = 0
If strVal.Length > 1 Then
For k As Integer = 0 To strVal.Length - 1
tmpDigitSum += strVal.Substring(k, 1)
Next
If tmpDigitSum = 3 Then Return False
End If

'If a number's square root is an integer, it's a composite
If System.Math.Sqrt(tmpVal) = CInt(System.Math.Sqrt(tmpVal)) Then Return False

'If it's not divisible by itself, it's not Prime
If tmpVal Mod tmpVal <> 0 Then Return False

Dim MaxVal As Long = System.Math.Sqrt(tmpVal)

For k As Long = 2 To MaxVal
If tmpVal Mod k = 0 AndAlso k <> 1 Then
Return False
End If
Next

Return True
End Function

Java

Posted by – February 22, 2010

I don’t just hate Java. I loathe it.

In the past, I’ve done everything I can do avoid using it.

If I want to develop for Android, though, I guess I need to bite the proverbial bullet and find a copy of “Java For Dummies”.

There are a few somewhat niche things I’d like to do with my phone that there simply aren’t applications for yet.

The only mildly-practical thing I might make is a bluetooth-based remote control app for my Playstation 3. And, really, that’s just more about teaching myself than something I’d actually use much of.

Other than that, I have two main “pet projects” I’d like to get working.

The first application I want to make really just comes down to my desire to have things as automated as possible when it makes sense. In this case, I have a podcast app (Google Listen) which I only listen to when I’m in the car. Since my car’s stereo uses Bluetooth, I’d like to launch Google Listen when it detects the car stereo (which is only going to be while the car is powered on) and close it when the signal is lost (if it was automatically launched earlier). Granted, I could probably use the “Locale” app for that, but — hey — that costs money and is not nearly as much fun as making something myself, right? ;)

The second project I have in mind, ties in with my various GPS-based social networking apps (FourSquare, Loopt, BrightKite, etc.). Essentially, what I’m looking to do is to “check in” at my favorite places if I’ve been there for at least x-amount of minutes and I haven’t already checked in recently (whether manually or via this program). All of these have APIs that can be tied into, so it shouldn’t be TOO hard. I’d just need to make sure not to abuse the GPS too much or it’ll drain my battery… There are some way to ensure the GPS only comes on when the phone gets close, though, by looking at nearby cell towers or wifi networks, for instance. It’s not fool-proof, but probably would be better than having the GPS running all of the time.

To The Root Of The Issue

Posted by – February 22, 2010

I’ve had the MyTouch 3G from T-Mobile for a while now. It’s a good, solid phone. There are a lot of nice apps and features and I instantly fell in love with the Android OS. It was a new experience and I really liked doing stuff on the phone.

Still, that feeling of ‘newness’ only lasts for so long…

Last week, I rooted it and installed the latest stable Cyanogen build. It’s been an absolutely wonderful experience. And really was a night-and-day difference between the official build and the custom ROM.

Plus, there are all sorts of neat tricks to eek out even more benefits. So far, my favorite is simply referred to as the “10MB hack”. The result is an extra 10MB of system memory to play with. Granted, that isn’t a WHOLE lot, but when you’re talking about smart-phones, every little bit counts.

Do I Look Fat In These Pixels?

Posted by – February 17, 2010

As I mentioned in my A New Year’s (Image) Resolution post, I’ve had a side project that requires dealing with images that come in at varying resolutions. Regardless of resolution, though, they all have the same basic requirements. I need to be able to “stamp” the pages with a dynamic header text, the quality needs to remain high enough that they can be viewed/printed, and — ideally — I need to have the header text be relatively the same size once it’s scaled on the screen or printed.

I think I’m a little closer to where I want to be, but it’s still not quite ideal.

I have a font object that’s 10-point bold “Courier New”. I use a Generic Typographic string format with No Clip and Word Trimming. I then use the MeasureString method on my graphics object to store the string size. Once I have that, I basically just subtract the height of that object from the width and height of my target rectangle and offset my starting position of DrawImage accordingly.

What I had hoped it would do is, if writing my header required 4mm of height, I’d scale the image down enough to give me 4mm of room on both sides (to keep the same aspect ratio) and write the header text. Similarly, if the header text somehow required an inch of height, it’d scale down so there was an inch of room.

It does seem to work, but just not as good as I had hoped. On some images, the header text was very close to the original fax text (which I want). In others, though, the spacing was a bit more pronounced and I’m not quite sure why just yet.

Ideally, what I want to do next, is have a way to determine the ideal font size based on the image. If I’m dealing with a basic image at 1275×1755 (at 96dpi H-Res and 96dpi V-Res), I would need a different size font than if I was working with a 1728×1052 image (at 203dpi H-Res and 98dpi V-Res).

I just haven’t quite figured out how I’ll actually DO that… yet :)

Actually, I take that back… my true ideal solution is to toss the text on the top or bottom of the page in a spot that isn’t being used a not have to mess with the scaling at all. But that’s more of a Phase-II plan…