utf-8 - Dave's Blog

Infrared Paint Link Roundup

2009 May 29, 2:50

I like the idea of QR codes, encoding URLs and placing them on real world objects, but the QR codes themselves are kind of ugly. To make them less obvious I thought I could spray QR codes on to an object with an infrared reflective paint and shine infrared light on the QR codes, since most cameras, for instance the camera in my G1 phone, pick up infrared that our eyes do not.

In my search for infrared paint I've found a seller of IR ink (via programming forum) and an Infrared Paint Recipe (via IR FAQ).

In looking for this paint I've found that it comes up a lot in relation to the military for things like paint markers that are visible at night with proper equipment, and paint that absorbs IR light to make vehicles less obvious to night vision goggles. Even though the first reflects infrared light and the second absorbs it websites end up refering to both as infrared paint which made it difficult to search.

Additionally I found links to some other geeky infrared projects:

• Infrared goggles that block out all light except for the edge of infrared light that humans can perceive.
• A project to make infrared patterns and paint to screw with tourist video/photos.

ir paint technical ir infrared qr qr code

The 'Is It UTF-8?' Quick and Dirty Test

2009 Mar 6, 5:16

I've found while debugging networking in IE its often useful to quickly tell if a string is encoded in UTF-8. You can check for the Byte Order Mark (EF BB BF in UTF-8) but, I rarely see the BOM on UTF-8 strings. Instead I apply a quick and dirty UTF-8 test that takes advantage of the well-formed UTF-8 restrictions.

Unlike other multibyte character encoding forms (see Windows supported character sets or IANA's list of character sets), for example Big5, where sticking together any two bytes is more likely than not to give a valid byte sequence, UTF-8 is more restrictive. And unlike other multibyte character encodings, UTF-8 bytes may be taken out of context and one can still know that its a single byte character, the starting byte of a three byte sequence, etc.

The full rules for well-formed UTF-8 are a little too complicated for me to commit to memory. Instead I've got my own simpler (this is the quick part) set of rules that will be mostly correct (this is the dirty part). For as many bytes in the string as you care to examine, check the most significant digit of the byte:

F:

This is byte 1 of a 4 byte encoded codepoint and must be followed by 3 trail bytes.

E:

This is byte 1 of a 3 byte encoded codepoint and must be followed by 2 trail bytes.

C..D:

This is byte 1 of a 2 byte encoded codepoint and must be followed by 1 trail byte.

8..B:

This is a trail byte.

0..7:

This is a single byte encoded codepoint.

The simpler rules can produce false positives in some cases: that is, they'll say a string is UTF-8 when in fact it might not be. But it won't produce false negatives. The following is table from the Unicode spec. that actually describes well-formed UTF-8.

Code Points	1st Byte	2nd Byte	3rd Byte	4th Byte
U+0000..U+007F	00..7F
U+0080..U+07FF	C2..DF	80..BF
U+0800..U+0FFF	E0	A0..BF	80..BF
U+1000..U+CFFF	E1..EC	80..BF	80..BF
U+D000..U+D7FF	ED	80..9F	80..BF
U+E000..U+FFFF	EE..EF	80..BF	80..BF
U+10000..U+3FFFF	F0	90..BF	80..BF	80..BF
U+40000..U+FFFFF	F1..F3	80..BF	80..BF	80..BF
U+100000..U+10FFFF	F4	80..8F	80..BF	80..BF

test technical unicode boring charset utf8 encoding

Excercise Bike and Tacoma Screw Products

2008 Jan 13, 11:07

Sarah and I got an exercise bike on sale and when attempting to put it together found that it was missing a bag of about ten different screws. The manufacturer website said we could order a replacement bag for thirty dollars (!!) but since the instructions listed the various kinds of screws we needed I figured we could just go to a hardware store and buy them.

We started at Home Depot because I didn't know better. The screws are all listed in metric sizes which is apparently uncommon and a helpful senior worker forwarded us to McLendons whose stock was better but we were again redirected this time to Tacoma Screw Products.

Tacoma Screw Products is great! See them for your hardware needs first! The store has a back area with every kind of screw ever. I felt a little out of place as as all the customers looked like contractors. The employee who helped me explained the various options I had in screws as the bike instructions weren't as explicit as they could have been. In the end I bought all my screws for only one dollar (much better than $30!) and they all fit correctly.

screw bike personal tacoma screw products nontechnical

Second Life Translator

2007 Jul 4, 10:58Hackdiary
I really enjoy reading Matt Biddulph's blog hackdiary. An entry some time ago talked about his Second Life flickr screen which is a screen in Second Life that displays images from flickr.com based on viewers suggested tags. I'm a novice to the Second Life scripting API and so it was from this blog post I became aware of the llHTTPRequest. This is like the XMLHttpRequest for Second Life code in that it lets you make HTTP requests. I decided that I too could do something cool with this.

Translator
I decided to make a translator object that a Second Life user would wear that would translate anything said near them. The details aren't too surprising: The translator object keeps an owner modifiable list of translation instructions each consisting of who to listen to, the language they speak, who to tell the translation to, and into what language to translate. When the translator hears someone, it runs through its list of translation instructions and when it finds a match for the speaker uses the llHTTPRequest to send off what was said to Google translate. When the result comes back the translator simply says the response.

Issues
Unfortunately, the llHTTPRequest limits the response size to 2K and no translation site I can find has the translated text in the first 2K. There's a flag HTTP_BODY_MAXLENGTH provided but it defaults to 2K and you can't change its value. So I decided to setup a PHP script on my site to act as a translating proxy and parse the translated text out of the HTML response from Google translate. Through experimentation I found that their site can take parameters text and langpair queries in the query like so: http://translate.google.com/translate_t?text=car%20moi%20m%C3%AAme%20j%27en%20rit&langpair=fr|en. On the topic of non US-ASCII characters (which is important for a translator) I found that llHTTPRequest encodes non US-ASCII characters as percent-encoded UTF-8 when constructing the request URI. However, when Google translate takes parameters off the URI it only seems to interpret it as percent-encoded UTF-8 when the user-agent is IE's. So after changing my PHP script to use IE7's user-agent non US-ASCII character input worked.

In Use
Actually using it in practice is rather difficult. Between typos, slang, abbreviations, and the current state of the free online translators its very difficult to carry on a conversation. Additionally, I don't really like talking to random people on Second Life anyway. So... not too useful.personal translate second-life technical translator sl code google php llhttprequest