Gl.ib.ly - Computers

Doing OCR on linux/Mac

nospam@example.com (Tariq) — Mon, 27 Jul 2009 12:03:45 -0600

Yesterday somebody gave me a USB key with ~1000 JPEGs on it. Each JPEG was a scanned page, ugh, and the task was to find some useful information about topic X. Now each JPEG was about 1-2mb and I needed to do something useful with these images quickly. So what follows is quick walk through of how to do Optical Character Recognition (OCR, that means taking silly image files and ripping out any text identified in them) on Linux or in my case a Mac.

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Encoding audio and removing file extensions from files

nospam@example.com (Tariq) — Fri, 24 Jul 2009 09:51:59 -0600

Earlier today I got a massive SCORM object that contained lots of mp3 files. They were all high quality files, so I wanted to cut them down in size for web use. For this purpose I am using ffmpeg which you can easily get for Windows, Linux or Mac. I tried the following on a Mac, but it should also work on Linux (paths permitting) and on Windows if you are using something like cygwin.

I highly recommend you get familiar with ffmpeg as it is amazingly useful. Just check out the man pages; swf to avi, avi to something that works on ipods, all a breeze!

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Searching compressed Apache logs

nospam@example.com (Tariq) — Tue, 23 Jun 2009 15:50:46 -0600

From time to time things tend to go wrong and systems tend to go crazy. Sometimes these errors are more of nuisance than anything else, an intermittent annoyance you'd prefer not to investigate -- trawling through logs is a pain in the backside. Now you need to take a peak at those compressed Apache error log files, ugh! Well before you look for suitable places to hang some rope try running some expressions across a certain number of files. Normally you'd only want to look at logs for the last 7 days, so lets give that a go.
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The command prompt has been disabled by your administrator?

nospam@example.com (Tariq) — Thu, 05 Feb 2009 08:10:00 -0700

I came across an old enough post on Didier's blog about Group policies that have disabled cmd.exe from running. Didier mentions a few ways to get cmd.exe to run. The suggestion I like the most is to find the DisableCMD string in cmd.exe and change it to DisableAMD using a hex editor. Thankfully there is a tool which will allow us to patch cmd.exe in one tiny line.
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Programmatically creating cool images

nospam@example.com (Tariq) — Fri, 09 Jan 2009 09:52:01 -0700

One of the elective courses in the final year of my undergraduate degree course in software engineering was Graphics I (and later followed by Graphics II). For our Graphics I project we were first shown Pixar's famous lamps short. After it had played we were told our project would be to do our own 3d animation greater than 1 minute in duration. The only restriction was that all objects needed to be generated in the program, so no loading up really complicated open source stuff. I wrote a 3d animation of fighting stick men which was way more than I could chew at the time so they ended up shooting each other from a distance :-p. Anyway since then I have been in love with generating all types of images using pure code.
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My experiences with Google Chrome

nospam@example.com (Tariq) — Thu, 08 Jan 2009 16:19:07 -0700

On September 1, 2008 Google announced a A fresh take on the browser. I greeted this news enthusiasticly; some people believed that google was mobilizing to crush Microsoft in an all out internet browser war. At the same time Firefox crackpots (I am nearly one :op) riled at how inferior Google Chrome was or still *is* -- what no browser extensions? I decided to hold back on what I thought and give it a fair chance.
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Deleting specific emails from the postfix mail queue

nospam@example.com (Tariq) — Thu, 08 Jan 2009 12:34:18 -0700

A week ago a development database server lost power, which is usually no big deal only that I have some reporting scripts that run every 5 minutes for each database. When these databases became unavailable they (the scripts) like to send me a quick mail telling me what went wrong. The network switch also was out of action so there was no route to the outside world from this small development network. The server lost power for three days and a massive amount of mail built up in the mail queue. When power was restored the SPAM started pouring in.
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All configuration variables in Moodle code?

nospam@example.com (Tariq) — Mon, 15 Dec 2008 12:15:37 -0700

Sometimes Moodle introduces some nice new configuration variables and I like to make sure that I know what they are and where they are. So to begin my investigation without heading off to the web I use the following command to get me a sorted list of the $CFG variables.
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Creating an HTML file with white space traces

nospam@example.com (Tariq) — Tue, 09 Dec 2008 08:29:00 -0700

Once upon a time I was comparing some Java files. Now one way to find plagiarism among students who share program code is to look at the white space traces in a file. Students typically try and edit the source code: changing variable names and function names; however, they usually fail to conceal the original author's white space patterns. White space consists of characters which don't appear on screen such as spaces, tabs, and new line characters. Anyway you can catch lots of cheaters by looking at the white space patterns in files ... maybe that's another blog entry, so back to this one.

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Getting logins per day in Moodle

nospam@example.com (Tariq) — Tue, 02 Dec 2008 08:59:00 -0700

Today I got the urge to see how many logins we had on some of our Apache servers in November. We host more than one moodle site on one server and so I wanted the total number of logins we handled. As usual this ended up becoming an awkward but useful one liner.
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