FilipiVianna

Resizing images and generating animated gifs

2011-11-23T09:37:00.000-08:00

After writing my last posts (Plotting memory usage on console and More trickery with gnuplot dumb terminal), I had to put here some lines used to make the screenshot I'd put there.
To resize all screen shot frames:

ls -1 *.png | cut -d . -f 1 | while read line ; do convert $line.png -resize 60% $line.mini.png; done

In stead of resizing the image, they can be cropped:

ls -1 *.png | cut -d . -f 1 | while read line ; do convert $line.png -crop 400x270+92+37 $line.mini.png; done

To make the animated gif
convert -delay 100 -loop 0 screenshot0*mini.png screenshot.gif

More trickery with gnuplot dumb terminal

2011-11-23T07:38:00.001-08:00

In my post "Plotting memory usage on console" the chart doesn't panned the data.
Now, using a named pipe, the effect got a little bit nicer.
First we have to run the memUsage.sh script to get a file filled with memory usage info:
./memUsage.sh > memUsage.dat &
Then we have to create a named pipe:
mkfifo pipe
Now we have to run another process to tail only the last 64 lines from the memUsage.dat
while [ 1 ]; do tail -64 memUsage.dat> pipe; done &
And now we just have to plot the data from the pipe:
watch -n 1 'gnuplot -e "set terminal dumb;p \"pipe\" with lines"'
And that is it!

Plotting memory usage on console

2011-11-23T03:09:00.001-08:00

This is just a simple hack to play around with gnuplot set to dumb terminal (character console), doesn't meant to be serious application.

First I had written a bash scritp to log memory usage a while ago:

So, while running this script in background (./memUsage.sh > memUsage.dat &), logging the data, the memory usage information can be plotted with gnuplot and watched in real time:
watch -n 1 'gnuplot -e "set terminal dumb;p \"memUsage.dat\" with impulses"'

The chart can be plotted with lines, with impulses or any gnuplot style option.

ftdi232 permission on Ubuntu

2011-11-22T11:29:00.000-08:00

I'am using the ftdi chip with bitbang mode to control some hardware with linux.
Every time a copy my software to a new desktop, it always toke me hours to figure out why it has not permission to run the bitbang mode as a regular user.
Every website or forum I look around tells me about the udev, but I check back on the working desktops and there is no udev rule for the ftdi hardware. And after trying to force permissions with chgrp and chmod directly on /dev/bus/usb/* I figured out that I had to master at least a little about udev rules.

Checking with a little more care at a working machine I´ve found a Virtualbox instalation which created a udev rule for the virtualbox usb driver. Changing that rule to be used with the FTI chip I do the following steps, with had worked perfeclty:

Create the file /etc/udev/rules.d/10-ftdi.rules

Write on it:
SUBSYSTEM=="usb_device", GROUP="dialout", MODE="0664"
SUBSYSTEM=="usb", ENV{DEVTYPE}=="usb_device", GROUP="dialout", MODE="0664"

I have to make sure my user belongs to the dialout group, reboot the machine and that´s done.

powerpoint slides to jpeg

2011-08-25T18:03:00.000-07:00

Looking for some way to convert power point slides to JPG, I've found this site:

http://www.commandlinefu.com/commands/browse

It has tons of good linux command line tips.

And here is the tip about the pdf to jpg which brought me there:

http://www.commandlinefu.com/commands/view/719/convert-pdf-to-jpg

And to convert the powerpoint to pdf before, one can issue the unoconv command:

unoconv -f pdf slides.ppt

Books

2011-08-12T19:02:00.000-07:00

Tonight I was home alone with my kid. Fortunetly for us (the kid and me) our PC is connected to the TV set. So, he watched his favorites DVDs, while I had Google Reader in play mode with slide show enabled and side by side windows.

After playing the DVDs a dozen times, Google Reader showed this e-book post.

PostgreSQL is my database of choice, so this book will be very appreciated.

The PostgreSQL e-book is at:

http://www.commandprompt.com/ppbook/

Mac OS X in Linux via VirtualBox (as guest OS)

2011-08-12T05:15:00.000-07:00

That is some thing I want to do for quite some time:

Install Mac OS X Snow Leopard as a guest OS in a VirtualBox Linux host

http://martinml.com/en/how-to-install-mac-os-x-snow-leopard-in-virtualbox/

http://blog.nguyenvq.com/2010/12/04/mac-os-x-in-linux-via-virtualbox-as-guest-os/

http://myhack.sojugarden.com/guide/

JavaScript Pie charts

2011-08-09T07:27:00.000-07:00

Considering the "Warning against using pie charts", I'm needing to produce a couple of jquery/json ajax enabled piecharts within a simple webapp I'm designing.

There are some sort of ready to use examples:

Using various javascript libraries to create pie chart

JavaScript charts | Pie charts

dd over ssh

2011-08-01T10:46:00.000-07:00

Just to make some backups:

dd if=/dev/sda1 | gzip -c | ssh filipi@10.30.46.11 'dd of=/opt/backups/big/filipi/disk.image.gz'

Flash Calendar V2.0 to iCal

2011-08-01T05:57:00.000-07:00

The organization where I work uses a Flash Calendar to show holidays, special day activities and other public calendar. The Flash Calendar loads its events from a XML file which, in our case, is keeped really up to date. So I was willing to view those events on my Google Calendar screen, to better plan my meatings and so on.

After that, I had written a small wrapper to parse the XML and echo iCal output. It still not fully compatible with Flash Calendar XML, but for the uses of my organization is enougth.

I did put it on github.

https://github.com/filipi/swfcalendar2iCalWrapper

Tron CSS theme

2011-08-01T05:08:00.000-07:00

After two posts about the last Tron Legacy movie (Web Fonts, emacs, Tron Legacy and Interface design), and trying to make a Tron theme for my web apps. I decided to google for a Tron CSS theme... Wasn't a surprise Google came with Sassy Tron Theme, which includes the movie's touch keyboard entirely written with CSS.

Design Stencils

2011-07-29T10:13:00.000-07:00

We need to develop some interface sketch at one of our labs.
So would be good to have a collection of gui stencils to draw it in inkscape.

Yahoo has a beautiful stencils collection at: http://developer.yahoo.com/ypatterns/about/stencils/

And there is also the Axure at:
http://www.axure.com/widgetlibraries#Widget_Libraries

More on cross-compiling (Codeblocks targets)

2011-07-28T06:22:00.000-07:00

Following two old posts (Cross-compiling windows applications under linux with wine and DevC++ and Compiling win32 binaries on linux) here another post on cross-compiling windows applications on linux.

DevC++ has apparently been droped by its creators, as it has been years since its last release.

After that I am willing to migrate some projetcs to Codeblocks. To not loose to much productivity, I am using a windows vitual machine (Virtual Box) to compile my windows projects, with DevC++, Codeblocks and Borland C++ Builder.

But what I want most is to do everything from my emacs window. Until I can do it so, I am using Codeblocks which is a multiplatform IDE, running on Windows, Linux and Mac.

Codeblocks has a target option to its projects. One can set diferent target platforms for the same project. The same project can be opened on diferent Codeblocks versions, linux and windows for example, and, with the propoer target configuration, be compiled for windows and for linux even folowing different kind of dependencies at each platform.

Codeblocks wiki has a simple, but nice, tutorial on cross compiling wxWidgets with codeblocks.

plaNETlab

2011-07-27T12:16:00.000-07:00

Working in multiple labs sometimes worth new infos on different knowledge areas. As I am at LAD every Wednesday and Friday at afternoon, people there always came with news on high performance computing. Today, one former student visiting the lab told me about the PlaNETLab project, wich is s a global research network that supports the development of new network services. There are hosts spread trough many countries as shown on their map.

Interface design

2011-07-27T06:55:00.000-07:00

I am not a designer... much worst, I am an engineer. But I was always fascinated with beautyfull interfaces designed for movies. In speciall from last movies like Tron Legacy, Iron Man 2 and Avatar and one a little dated, LCARS from Star Trek.

Googling a little on "lcars avatar tron iron man interface design", I've found some awesome links:

Interesting user interfaces from sci-fi movies & tv?
http://ux.stackexchange.com/questions/998/interesting-user-interfaces-from-sci-fi-movies-tv

Visual effects of Tron: Legacy and beyond – conversation with GMUNK
http://www.pushing-pixels.org/2011/06/01/visual-effects-of-tron-legacy-and-beyond-conversation-with-gmunk.html
TRON Board Room
http://work.gmunk.com/#1190825/TRON-Board-Room

Iron Man 2 Case Study
http://perceptionnyc.com/node/68
http://www.behance.net/jose_ortiz
http://www.behance.net/gallery/IRON-MAN-II-Molecule-Discovery/573381
http://www.behance.net/gallery/IRON-MAN-II-Hologram-Armor-Suit-Development/570107
http://motionographer.com/features/prologue-iron-man-2/
http://prologue.com/projects/iron-man-2--2/groups/interfaces--3/galleries/interface-design--2

Sci-Fi Movie Interfaces: Why Transparent Screens Are Miserable to Use
http://www.switched.com/2011/03/16/sci-fi-movie-interfaces-why-transparent-screens-are-miserable-t/

How Can the Division of the Screen Enhance our Experience of Dimensionality?
http://davidtatnell.wordpress.com/2010/12/01/research-paper/

I hope to improve this blog design :-) and to put more content on desgin here.

Web page test

2011-06-02T16:49:00.000-07:00

An old friend which is working for an high volume web site just pass by for a short visit. Chatting a little about simple technicalities he gave me a tip about a web site which gives statistics about site performance.

http://www.webpagetest.org

They access your web site, from a location and web browser of your choice and give back to you lots of statistics about download time of your web site.

I have tested this blog, the results are at http://www.webpagetest.org/result/110602_F6_R879/

And the IDEIA's web site restuls:

http://www.webpagetest.org/result/110603_73_RDWS/

Using ffmpeg to encode a high quality video

2011-05-10T09:46:00.000-07:00

I had acquired some high quality images and was willing to encode them into a video, but ffmpeg default settings was always outputting a ugly video which had 1280x720, but with lots of artifacts.

After googling a little, I've found:

http://stackoverflow.com/questions/3561715/using-ffmpeg-to-encode-a-high-quality-video

Digging a little more on the comments I've found:

You need to specify the -vb option to increase the video bitrate, otherwise you get the default which produces smaller videos but with more artifacts.
Try something like this:
ffmpeg -r 25 -i %4d.png -vb 20M myvideo.mpg

So, the key was the -vb flag!

ffmpeg -i Image-%d.jpg -s 1280x720 -aspect 16:9 -r 24 -vb 20M teste.mp4

Web Fonts, emacs, Tron Legacy

2011-04-19T11:36:00.000-07:00

After read the jtnimoy blog, about how emacs got into Tron Legacy. I had noticed he had embedded a beautiful typeface on his site and I started to pay some attention on web fonts and the new Google service "Google Web Fonts".

They have a good collection of fonts available under an open source license.

Getting which browser access your site, from apache's logs

2011-04-12T10:31:00.000-07:00

I am developing a small web based system to run inside my sector here where I work. I had spend some time to make it compatible with the majority of web browsers available. I'm still not using html 5 and rendering dynamic graphics to png to display on Internet Explorer browsers. Even the PNG transparency is fixed to a solid background color for better rendering on Internet Explorer 6, so I decided to check which browser my colleges are using to access this small system.

To do it so, I used the follow line on my server's console:

cat /var/log/apache2/access.log | cut -d "\"" -f 6 | sort | uniq

Which had returned:
GbPlugin Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; InfoPath.1; InfoPath.2) Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; InfoPath.2) Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; InfoPath.2) Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; InfoPath.2) Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; InfoPath.2; OfficeLiveConnector.1.3; OfficeLivePatch.0.0) Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.16 (KHTML, like Gecko) Chrome/10.0.648.204 Safari/534.16 Mozilla/5.0 (X11; U; Linux x86_64; en-US) AppleWebKit/534.16 (KHTML, like Gecko) Ubuntu/10.04 Chromium/10.0.648.133 Chrome/10.0.648.133 Safari/534.16

So... nobody is using IE6. Good!

How to create stacked area graphs with Gnuplot

2011-04-12T04:40:00.000-07:00

Marco has a nice tutorial showing how to make stacked area charts using Gnuplot.

http://freesoftware.zona-m.net/how-to-create-stacked-area-graphs-with-gnuplot/

jquery plugin for mind mapping

2011-04-07T12:06:00.000-07:00

Looking for some jquery plugin for mind mapping, I've reached a stakoverflow conversation:
http://stackoverflow.com/questions/1374149/jquery-mind-map-think-map

And there is a cool demo here re-written with jquery:
https://github.com/kennethkufluk/js-mindmap

Last version (pure javascript)
http://kenneth.kufluk.com/google/js-mindmap/

And another tool, also interesting which worth a future review:
http://thejit.org/demos/

RRDtool, MRTG, Tobi Oetiker

2011-04-07T07:51:00.000-07:00

Tobi Oetiker has created two good tools for visualizations, th MRTG and the RRDtool. Both realy worth attention for their performance and in special the RRDtool for its versatility.

Changing SVG with inkscape from command line

2011-04-06T06:34:00.001-07:00

One can do more than simple convert vector to raster drawings with inkscape from the command line. In fact, there are other tools if the goal is just converting files, as rsvg and convert.

With inkscape, is also possible to change the drawing, using verbs.

From the inkscape man page, we can find the folowing example:

Duplicate the object with id="path1555", rotate the duplicate 90 degrees, save SVG, and quit:
inkscape filename.svg --select=path1555 --verb=EditDuplicate --verb=ObjectRotate90 --verb=FileSave --verb=FileClose

Googling a little on inkscape "--verb", I did find more examples, a list with the available verbs and details from the inkscape wiki.

On Tuftefying gnuplot

2011-03-28T05:26:00.000-07:00

Marcus Ritt has a nice tutorial on how to make gunplot graphics a little more Tufte.

http://www.inf.ufrgs.br/~mrpritt/doku.php?id=tufte

And Technolope also has some considerations on Tufte and gnuplot.

Latex following Edward Tufte

2011-03-20T08:52:00.000-07:00

I was putting some sparklines at an web app I am designing. I am using the "Sparkline PHP Graphing Library" which is a well written PHP library for generating the famous sparklines created by Edward Tufte. So I was wondering which another advice I could pick up from Master Tufte... I went googling arround for Edward Tufte and a bunch of links came up but, the one which most called my attention was a Tufte-inspired LaTeX class for producing handouts, papers, and books. The samples provided by the web site are really well designed.

Javascript, visualization and statistics (Protovis and Jstat)

2011-03-19T16:03:00.000-07:00

Last week I got faced with two very interesting libraries.

Protovis
Protovis uses JavaScript and SVG for web-native visualizations. Protovis composes custom views of data with simple marks such as bars and dots.

Unlike low-level graphics libraries that quickly become tedious for visualization, Protovis defines marks through dynamic properties that encode data, allowing inheritance, scales and layouts to simplify construction.

jStat

jStat is a statistical library written in JavaScript that allows you to perform advanced statistical operations without the need of a dedicated statistical language (i.e. MATLAB or R).

Read Write Web has also an article about other 20 JavaScript Libraries for Data Visualization

Let’s use video to reinvent education: Salman Khan on TED.com

2011-03-14T11:05:00.000-07:00

Acer Aspire One BIOS Recovery

2011-02-08T05:19:00.000-08:00

From (http://macles.blogspot.com/2008/08/acer-aspire-one-bios-recovery.html)

The Acer Aspire One has a built-in BIOS recovery routine, which can boot into a minimal BIOS environment via a special boot block to re-flash the BIOS, even if the system does not pass POST and does otherwise not boot anymore. This procedure is also known as Crisis Disk.

First format an USB flash drive with FAT. It does not need to be bootable.

Download the latest BIOS, and extract all files. Put both FLASHIT.EXE and the BIOS file with FD suffix in the root directory of the flash drive. The files must not be in a folder. Rename the BIOS file to ZG5IA32.FD before proceeding. It only works with this exact filename.

Turn the AA1 off, and verify both battery and AC adapter are plugged in.

Press Fn and Esc simultaneously, keep them pressed and press the power button. Release Fn+Esc after a few seconds. The power button starts blinking at this point. Press it once. The AA1 will now access the files on the flash drive and initiate flashing the BIOS. After a while the power button stops blinking, and the AA1 reboots by itself. Wait patiently.

If it doesn't reboot, but keeps blinking, wait at least a few minutes before turning it off, and try again.

BIOS

Open Source Your Rave with OpenLase

2011-01-18T02:35:00.000-08:00

Open Source Your Rave with OpenLase: "

Without a doubt, Laser Projectors are a great way to project large, bright images on any surface you can imagine. With a high enough quality projector and software package, excellent images and visualizations can be displayed in real time. [marcan], of the openkinect project, decided that there were not any open source laser projection packages out there that suited his wants or needs, so logically he decided to write his own. Because home-made laser projectors often use the audio out port of a PC, building the framework on top of the JACK unix sound software to control the hardware made perfect sense. OpenLase includes plugins for audio visualizations, 2D and 3D gaming, as well as converting video streams into laser format in real time.

Be sure to check out the Chaos Communication Congress presentation [marcan] gave after the break, as well as all the extra demo videos on his website.

How to fix Emacs 23 Huge ungly font on Lucid

2011-01-14T03:01:00.000-08:00

Since I've upgraded to Ubuntu 10.04 (Lucid) Emacs 23 now has beautiful antialiased fonts, but I like the old bitmaped X11 "fixed" font. I do use a .Xresources file to setup emacs default font.

This is my emacs section at .Xresources

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

! emacs, xemacs

!emacs*Background: DarkSlateGray

emacs*Background: Black

!!!emacs*Foreground: Wheat

emacs*Foreground: White

emacs*pointerColor: Red

emacs*cursorColor: Red

emacs*bitmapIcon: on

emacs*font: fixed

!!!emacs*font: 9x15bold

!!emacs*geometry: 100x40+20+20

But for my surprise using this setup emacs launches with a ugly huge serif font.

I tried to launch emacs with -fn fixed but the ugly font did still there.

So I checked at my /etc/X11/fonts/misc/xfonts-base.alias, which is the file where fixed font is declared. And it was there:

fixed -misc-fixed-medium-r-semicondensed--13-120-75-75-c-60-iso8859-1

And which had called my attention, was that 6x13 font alias had the same properties as the fixed:

6x13 -misc-fixed-medium-r-semicondensed--13-120-75-75-c-60-iso8859-1

So launching emacs with -fn 6x13 gave me back the look and feel I wanted. After that I changed my .Xresources to use 6x13 instead of fixed. And it is done.

I don't know what was done with emacs but this little work around fix the Huge Ugly font issue which I had see while I was googling arround on that subject.

Extended desktop at the login screen in ubuntu

2011-01-12T04:07:00.000-08:00

I have an ATI Raden dual head at my desktop here at my job. I like to use WindowMaker as my window manager of choice, but since I had upgraded to Ubuntu 10.04 Lucid, WindowMaker is showing some issues regarding the dual monitor setup. WindowMaker follows the login screen (GDM) monitor setup and when I launch a gnome-session, things get messed up.

The first solution which came to my mind is to make gdm aware of the two monitors.

"Googling" around I've found two usefull links:

https://help.ubuntu.com/community/MultiseatOneCard

http://ubuntuforums.org/showthread.php?t=1611704

Following the first section of the first link ("Extended desktop through both monitors") I've wrote my new xorg.conf file:

Section "Monitor"
 Identifier      "monitor0"
EndSection

Section "Monitor"
 Identifier      "monitor1"
 Option          "RightOf" "monitor0"
EndSection

Section "Device"
 Identifier      "card0"
 Driver          "radeon"                     ### EDIT ###
 Option          "Monitor-DVI-0" "monitor0"   ### EDIT ###
 Option          "Monitor-DVI-1" "monitor1"   ### EDIT ###
EndSection

Section "Screen"
 Identifier      "screen0"
 Device          "card0"
 Monitor         "monitor0"
 DefaultDepth    24
 SubSection "Display"
         Depth   24
         Virtual 1280 1024                   ### EDIT ###
 EndSubSection
EndSection

Section "ServerLayout"
 Identifier      "default"
 Screen          "screen0"
EndSection

And everything worked just fine.

SVox PicoTTS (from Android) is available on Ubuntu 10.10

2010-10-13T09:47:00.000-07:00

Another repost. This pos, form acassis is special for my quest to Voice Picking with freesoftware. More resources on SVox can be found at Open Hand Set Alliance www.openhandsetalliance.com.

acassis: "

Finally SVox PicoTTS (from Android) is available on Ubuntu 10.10.

To install it execute:

$ sudo apt-get install libttspico-utils

To test execute it:

$ pico2wave -w /tmp/test.wav 'Hello World'
$ aplay /tmp/test.wav

Transparent image overlays in OpenCV

2010-09-28T19:11:00.000-07:00

http://www.aishack.in/2010/07/transparent-image-overlays-in-opencv/

GPU Processing and Password Cracking

2010-09-28T05:59:00.000-07:00

GPU Processing and Password Cracking: "

Recently, research students at Georgia Tech released a report outlining the dangers that GPUs pose to the current state of password security. There are a number of ways to crack a password, all with their different pros and cons, but when it comes down to it, the limiting factor in all of these methods is processing complexity. The more operations that need to be run, the longer it takes, and the less useful each tool is for cracking passwords. In the past, most recommendations for password security revolved around making sure your password wasn’t something predictable, such as “password” or your birthday. With today’s (and tomorrows) GPUs, this may no longer be enough.

Although the article never mentions them by name, the newest tools in password cracking are based around two tools, nVidia’s CUDA and AMD’s Stream SDKs. These tools allow programs to be written in C that can be broken up and utilize the parallel nature of the hardware that is usually optimized for graphics. GPUs are much better at large-scale mathematical operations than CPUs because of this parallel layout. Chances are, if you have a somewhat recent graphics card, it is probably compatible with either CUDA or Stream, and if you already know C, you have all the tools necessary to get started.

The lesson to learn here, the longer or more complex a password is, generally the safer it is. Because of this, a number of tools, both software and hardware, may become more and more popular, or necessary, to accommodate this need.

Open source substituto para o LabView

2010-09-25T18:14:00.000-07:00

Open source substituto para o LabView: "

Ha algum tempo recebemos na empresa onde trabalho a visita de um representante da National Instruments que demonstrou varias placas e o LabView para utilizar como ferramentas para diagnostico e testes de placas na nossa linha de producao.

Na epoca eu comecei a imaginar algumas solucoes open source para fazer as mesmas funcoes da solucao apresentada pela NI, uma vez que a nossa empresa preferiu nao comprar a solucao deles.

Hoje resolvi documentar as quais software e placa eu utilizarei para implementar uma solucao equivalte ao da NI:

- Scilab: http://www.scilab.org

- Comedi: http://www.comedi.org

- USBDUX: http://www.linux-usb-daq.co.uk/prod2_usbdux/

More on Web3D

2010-09-13T04:18:00.000-07:00

Following some posts on standards for 3D (Web CAD and Pseudo 3D game) here are some other links on Web3D:

http://www.web3d.org/

http://www.web3d.org/x3d/x3dom/

http://www.teratec.eu/gb/forum/atelier_3.html

http://www.x3dom.org/

IGES STEP data formats links

2010-09-08T07:48:00.000-07:00

I have to write a full post about this. But for now, just some links

http://machinedesign.com/article/whats-new-with-iges-and-step-0524

http://www.wiz-worx.com/iges5x/gehaeuse/

http://www.llach.com/cimcad3d.htm

Another home-built laser projector

2010-08-23T13:15:00.000-07:00

From my Google Reader:

Another home-built laser projector: "

[Jarrod] sent us a link to this home-built laser projector after seeing a different projector that we featured yesterday. This system is fundamentally different. [ChaN], who finished the project several years ago, didn’t use a loudspeaker to move the mirrors, but instead build his own closed-loop Galvanometers. Two of these are controlled by an ATmega64 to produce incredibly clean and accurate vector images. It’s not just the images that are impressive, his hardware is laid-out with skill and forethought that make hiding it in a case a sacrilege.

Quickstart: SSH Public Key Infrastructure

2010-07-26T09:51:00.001-07:00

The following quickstart was copied from http://uaahosting.uaa.alaska.edu/axjww/sshkey/

By Jim Weller

The purpose of this document is to quickly step you through using
passwordless authentication to connect to servers using the SSH2
protocol. This document is unique in that it unifies all the clients
and servers under a single identity. This document is very coarse
and expects that you'll follow along with the videos and only
use the notes as a supplement.

Prerequisites

Commercial SSH client version 3.2 or higher installed.

ftp://ssh.com/pub/ssh
Commercial SSH Accession agent

ftp://ssh.com/pub/accession
PuTTY SSH2 Client Suite

http://www.chiark.greenend.org.uk/~sgtatham/putty/
OpenSSH environment. Cygwin shown here, but Linux, Mac X, BSD, Solaris and many others apply

http://www.cygwin.com/

Video Guides

Terse Text Notes


Generating Private and Public Keys

A - Pick a strong password. You'll need to remember it because you'll type it
a couple of times during this setup and once every windows login after that.

B - Generate a key using commercial SSH.
       1 edit->settings->keys->new key
          Key Type: DSA
          Key Length: 2048
          NEXT>
          name: dsa204_commssh
          Pasword: leave blank
          Comment: leave blank

C - convert the key to openssh private key format and set a password
on it. You'll have to move the key you created above to a location
where you can use ssh-keygen from the openssh package. Either cygwin
or an openssh unix box (like linux/mac) or whatever you have handy.

       # convert commercialssh private to openssh private
       ssh-keygen -i -f dsa1024_commercial > dsa1024_openssh
       # convert openssh private to opensshpublic
       ssh-keygen -y -f dsa1024_openssh > dsa1024_openssh.pub
       # convert openssh public to commercialssh public
       ssh-keygen -e -f dsa1024_openssh.pub > dsa1024_commercial.pub
       # finally set a password on openssh private
       ssh-keygen -p -N password -f dsa1024_openssh
     
D - go back to commercial ssh and change to the password to match.

E - Use puttygen to convert the openssh key to a putty key. Set your
password while doing it. You only need to save a private key.

Now you have 3 identical private key files with the same passphrase
for each of the three different clients. The private keys must be
kept very secure. Never share them or leave them lying around. Make a
backup copy to put in a vault, firebox, or ziploc bag.

You also have two public key files, one for each brand of server.
These are not critical files. You'll share them with the servers you
want to connect to. As shown above, you can always re-create the
public keys from the private keys.

Just remember the server gets the public key of its flavor. The client
uses the private key of its flavor.



Making the Connection

Here are all the connection combinations

c - commercial ssh
o - openssh
p - putty

Client -> Server
----------------
c -> c
o -> c
p -> c

c -> o
o -> o
p -> o


You don't have to learn all six. You just need to learn 5 things. 2
ways to put public keys on servers and 3 clients to connect using
private keys.


Servers

You have to connect to the server at least once with a password in
order to perform these operations. Very high security environments
might have someone else do this for you. Either way, you have
to have your account on the server configured to accept your
public key.

1 - OpenSSH server

connect to the server
# mkdir .ssh
# chmod 700 .ssh
# cd .ssh
copy the OpenSSH public key file and append it to authorized_keys

2 - Commercial SSH server

connect to the server
# mkdir .ssh2
# chmod 700 .ssh2
# cd .ssh2
copy the commercial ssh public key file and put it in it's own file on the server
add a line to the authorization file to reference your key

Clients

By default you have to authenticate against your key every time you
connect to a server. This is good for security because you never send
a password over the wire; just big complex key strings. It's a pain
for you though. That's why most clients have an "agent" which runs in
the background on your computer and remembers the keys you
authenticated against. It's very convenient.

COOL!: Once the ssh-agent is running. You can eject your USB keychain. The
authentication ends when either you 1 kill the agent 2 exit your windows session
(killing the agent) 3 deallocate the key from the running agent.

1 - PuTTY and Pageant
start pageant.exe
right click the icon->add key
browse for your .PPK key
select the PPK key
type the key's password
launch putty sessions to servers having the key

2 - Commercial SSH Client and Accession
start accession
click add key
browse for your dsa2048_commssh
type the key's password
launch commercial ssh sessions to servers having the key

3 - OpenSSH client, ssh-agent, and ssh-add

ssh-agent bash -login
# bash -login could be another program like X or xterm or login
ssh-add /YourUsbKeyStore/dsa2048_openssh
# type your password
# launch openssh sessions to servers having the key



Getting your public key into banner
-----------------------------------
prod.alaska.edu (aka Toklat) is a commercial SSH server. So all the
notes I presented earlier about commercial ssh servers still apply.
prod.alaska.edu differs because statewide does not give you a standard
shell like bash or csh. They give you a homegrown menu system that
keeps you in a sandbox.

S for shell commands
D for directory commands
2-y-.ssh2 to make the .ssh2 directory
1-y-.ssh2 to change to the .ssh2 directory
R to return to the main menu
4 or 5-y-mykey.pub to edit a file with emacs or vi respectively (this is the jim.pub file from the videos). Paste your commercial public key into the file
4 or 5-y-authorization add 'Key mykey.pub' to this file just like in the videos

You're done. You should be able to SSH in using public key
authentication. I don't know yet how this relates to you password on
glacier, but I assume you'll never need to worry about it which is
fine as this is a billion times more secure.

Free Open Source Parametric 3D CAD on Linux

2010-07-26T05:43:00.000-07:00

The folks looking for a free and open source option for a Parametric 3D CAD have theirs choice now. HeeksCAD is a parametric 3D CAD, based on the open source modeler OpenCascade.

Actually it is for Linux and Windwos. It uses WX Widgets as its widget set.

The HeeksCAD site lacks on screenshots, as long as they are keeping a good work on the software... (let the community provides the screenshots ;-)

Googling a little we can found a good discussion in a forum at

http://www.linuxgraphic.org/forums/viewtopic.php?f=41&t=5728 (it is in French)

From the forum discussion above, I had extracted the following shots:

I had already used the Salome (another OpenCascade based tool), but the CAD it provides where more for geometry design for finite element pre and post processing. Diferent from Salome, HeeksCAD has much more functionalities from CADs like Pro/Engineer and SolidWorks.

I have around 8 years of experience in Pro/Engineer and 5 years using SolidWorks, I had no difficult to start modeling on HeeksCAD.

There are another Free and Open Source CAD based on OpenCascade. I had tried the gCAD, the FreeCAD and the HeeksCAD. The three are good, but the one which I was more productive was the HeeksCAD.

A few links from iheartrobotics.com

2010-07-09T16:14:00.000-07:00

A few links from http://www.iheartrobotics.com

http://code.google.com/p/structured-light/

http://meshlab.sourceforge.net/

http://openscad.org/

http://www.iheartrobotics.com/search?q=robot+vision

Security, auditing, etc

2010-07-09T10:05:00.000-07:00

Chating with an old friend, he told me to check these tools:
the hydra, at http://freeworld.thc.org/ and the Sipvicious at http://blog.sipvicious.org/.

Benoit Mandelbrot: Fractals and the art of roughness | Video on TED.com

2010-07-06T10:13:00.000-07:00

Benoit Mandelbrot: Fractals and the art of roughness | Video on TED.com

uSleep on windows (win32)

2010-07-01T07:25:00.000-07:00

I am facing a terrible issue regarding timing on windows.

Googling arround, I've found those infos:

Using QueryPerformanceCounter and QueryPerformanceFrequency APIs in Dev-C++
(http://yeohhs.blogspot.com/2005/08/using -queryperformancecounter-and_13.html)
QueryPerformanceCounter() vs. GetTickCount()
http://www.delphifaq.com/faq/delphi_windows_API/f345.shtml
How to time a block of code
http://www.cryer.co.uk/brian/delphi/howto_time_code.htm

And Results of some quick research on timing in Win32

http://www.geisswerks.com/ryan/FAQS/timing.html

With that I'm trying to write something like a uSleep function for windows:



#include<windows.h>

void uSleep(int waitTime){
__int64 time1 = 0, time2 = 0, sysFreq = 0;

QueryPerformanceCounter((LARGE_INTEGER *)&time1);
QueryPerformanceFrequency((LARGE_INTEGER *)&freq);
do{
QueryPerformanceCounter((LARGE_INTEGER *)&time2);

//  }while((((time2-time1)*1.0)/sysFreq)<waitTime);
  }while( (time2-time1) <waitTime);
}

There is also already a nanosleep at:

http://www.mail-archive.com/bug-gnulib@gnu.org/msg17746.html

and a usleep at MKSToolkit at:

http://www.mkssoftware.com/docs/man3/usleep.3.asp

Low cost microcontrolling

2010-06-30T17:48:00.000-07:00

I had a terrible issue at work today. We certainly have to give up from a windows controlled device, depending on time critical software to use a cheap and easy to find microcontroller.

Making a couple of phone calls to local electronics shops, draws me to one single option. Microchip's PIC 16F family.

So, let's go to PIC world:

http://www.grennan.com/picprog/ (Programming the PIC16F84 with LINUX)

The PIC16F84 is easily found at any electronics shops in my town. It costs around R$ 15,00 (fifteen reais), local brazilian currency, which is around US$ 8.45.

Programming PIC’s in Linux using C with SDCC

Intro to Programming PIC Microcontrollers in Linux

http://www.lancos.com/prog.html (PonyProg - GLP Serial devices programmer)

http://www.freenet.org.nz/sdcc/ (sdcc for PIC HowTo)

There is a good Spanish site about PIC projects at http://www.micropic.es/

Some free/open tools for hobbies

2010-06-26T14:33:00.000-07:00

[Open source PCB routing] MUCS-PCB - The University of Manchester School Of Computer Science PCB design software
http://intranet.cs.man.ac.uk/apt/projects/tools/mucs-pcb/

Ladder Logic for PIC and AVR
http://www.cq.cx/ladder.pl

SketchFlat: 2d CAD, with Constraints
http://www.cq.cx/sketchflat.pl

SOLVESPACE -- parametric 3d CAD
http://solvespace.com/index.pl

And for autorouting on kicad, there is the closed source freerouting

Multi (platform) browser CSS

2010-06-14T10:57:00.000-07:00

Reading an old friend's blog, I've seeing some tools he likes and there a particular one very suitable for my own needs. The blueprint CSS framework it uses the git hub. There is also some tips on using it with PHP (my favorite scripting language).

wxTerm

2010-06-14T10:42:00.000-07:00

IFTools has an free/libre open source (wxWindows license) communication terminal which uses a multi platform communications library.

Worth to take a look at:

https://iftools.com/opensource/download.en.php

Coffee machine robot

2010-06-14T10:33:00.000-07:00

Here at IDEIA we share a common spare time project. We want to build a robot which brings the coffee from the kitchen to our offices.

This project was a little inspired by the S.T.A.I.R. project from Stanford.

Looking around we've found the Mobile Robot Programming Toolkit (MRPT).

And perhaps worth to look at:

Arduino Ethernet Shield

and

Arduino Ethernet Library

[SIGGRAPH 2009]Build Your Own 3D Scanner: Optical Triangulation for Beginners

2010-06-10T19:41:00.000-07:00

There is an interesting course on 3D scanning at SIGRAPH 2009:

http://mesh.brown.edu/byo3d/source.html

Other good resources on 3D can be found at:
http://www.ieeta.pt/~pdias/Low_Cost_3D_Sensor/Low_Cost3DSensor.htm
http://www.ieeta.pt/~pdias/Camera%20Calibration/Camera%20Calibration.htm
http://www.awn.com/articles/tutorials/iinspired-3d-modeling-and-texture-mappingi-part-2/page/1,1
http://www-2.cs.cmu.edu/afs/cs.cmu.edu/user/rgw/www/TsaiCode.html
http://www-2.cs.cmu.edu/afs/cs/usr/rgw/www/HomePage.html

Pseudo 3D game

2010-05-31T21:17:00.000-07:00

How about make an pseudo 3D game with your company as th scenario?

This tutorial brings some examples:

http://dev.opera.com/articles/view/creating-pseudo-3d-games-with-html-5-can-1/

http://blog.nihilogic.dk/2008/07/wolfenflickr-3d-unlikely-mashup.html

Another demo:

http://www.benjoffe.com/code/demos/canvascape/

http://www.benjoffe.com/code/demos/canvascape/textures

Yet another javascript charting library

2010-05-31T21:00:00.000-07:00

I have to remember to check Grafico, another javascript charting library.

References:

http://dailyjs.com/2010/02/08/grafico/

Web CAD

2010-05-31T20:38:00.001-07:00

More on my quest to build something near a 3D visualizer with PHP and Javascript

Web 3D rendering:

http://www.uselesspickles.com/triangles/demo.html (this one uses less divs for the rendering)

http://www.treebuilder.de/default.asp?file=844112.xml

http://www.lutanho.net/svgvml3d/index.html

http://deanm.github.com/pre3d/

http://www.nihilogic.dk/labs/canvas3dtexture_0.2/

http://www.nihilogic.dk/labs/canvas3d/

3D Chrome Experiments

http://www.chromeexperiments.com/detail/monster/

Quering for "chrome experiments 3D shading" on google

http://www.chromeexperiments.com/detail/colorscube/

http://www.chromeexperiments.com/detail/orange-tunnel/

Some other Chrome experiments

http://www.chromeexperiments.com/detail/js-touch/

http://www.chromeexperiments.com/detail/3d-waveform/

Opening IGES/STEP files

http://www.opensg.org/wiki/PotentialContributions (with OpenSG)

http://www.ogre3d.org/forums/viewtopic.php?t=33146&highlight=&sid=ce193664e1d3d7c4af509e6f4e2718c6 (with Ogre)

http://code.google.com/p/heekscad/

Linux CADs

http://www.gcad3d.org/gCAD3D_en.htm

http://sourceforge.net/apps/mediawiki/free-cad/index.php?title=Main_Page

http://www.pythonocc.org/

Gaming

2010-05-31T17:23:00.002-07:00

Looking for some other software to load wavefront obj files I've found some interesting things on the gaming field:

http://tfc.duke.free.fr/ How to load Quane, Quake 2 and Doom3 characters with OpenGL

and

https://help.ubuntu.com/community/Doom3 How to setup Doom 3 on Ubuntu Linux

Loading wavefront obj files

2010-05-31T17:23:00.001-07:00

Looking for some other software to load wavefront obj files I've found some interesting thins on the gaming field:http://tfc.duke.free.fr/ How to load Quake, Quake 2 and Doom3 characters with OpenGL

and

https://help.ubuntu.com/community/Doom3 How to setup Doom 3 on Ubuntu Linux

Teaching Internship - Lab Class

2010-05-31T14:40:00.000-07:00

Tonight was my first lab class at my teaching internship.

We were preparing the undergrad students to make their final work for this class.
At this class professor introduced the "objloader" to them. For them to use it to open wavefront obj files for their animation work.
Professor also talked about the Accutrans3d.

The old Pro/Engineer also saves wavefront obj files.

Done - with Catull type face

2010-05-13T10:35:00.000-07:00

(Done with inkscape, following the tutorial cited on a previous post.)

Goostavo

Bookmarks on Finite Element Analisys

2010-05-11T10:45:00.000-07:00

http://www.freebyte.com/cad/fea.htm

http://www.engineersedge.com/engineering/Engineering_Downloads/Finite_Element_Software_Public_Domain/
http://geuz.org/gmsh/
http://www.range-software.com/
http://www.caelinux.com/

CAD Tutorials

2010-05-11T09:48:00.000-07:00

The Mechanical Engineering Department from the Carnigie Mellon University has placed some good tutorials on how to use the PTC Pro/Engineer CAD software.

It is an excellent material and is based on Pro/Engineer Wildfire 3, the last one with a Linux version.

It also includes Sheet Metal and Surfaces design and Finite Element Analisys using the Pro/Mechanica module.

Google Logo to Goostavo

2010-05-10T06:56:00.000-07:00

I was looking for a way to make a colored logo likes Google's to use for my kid's name.

Here is a simple tutorial on how to make the colored 3D effect with inkscape.

If I had the Catull type face, used by Google, it would be very cool to write my son's name (Gustavo) as Goostavo ;-) (done at May 13, 2010)

Catull Type face

(tutorial done with Catull, results at "Done - with Catull type face")

Kicad - crossplatform suite of programs for EDA

2010-04-22T05:04:00.000-07:00

Working in a place where people do projects on electronics using different platforms (windows and linux) certainly leads us to look for some tool which enables us to exchange our schematics and layouts through all this platforms. There is where Kicad came to help us.

And, to help us to use it, here is a short tutorial on how to do simple things with Kicad:

PS.:

Other interesting link on GNU/Linux and Electronics:

http://1010.co.uk/scrying_tech_notes.html

And on electronics:

http://www.electronics-lab.com/blog/?tag=power-supply&paged=2

Convert Scanned PDF Documents to Text without having to wait for google bots

2010-04-20T10:05:00.000-07:00

Working supporting old scientific hardware sometimes brings me some challenges. Usually, the manuals are only on paper and when there is a digital version it was digitized (scanned) .

Googling a little, came to me an article which relies on waiting for the google to index your files and OCR them. But there is an open source alternative.

Looking a little further, I did find another two articles at linuxquestions.org and at linux.com, on which I've found the tesseract-ocr. So to solve my issue, I had to first convert my PDF file to a bunch of TIF images, and so OCR them with tesseract. This way:

gs -dNOPAUSE -sDEVICE=tiffg4 -r300x300 -sOutputFile=page%03d.tif -- 1850_operators_manual.pdf

ls -1 *.tif | cut -d e -f 2 | while read line ; do tesseract "page"$line "page"$line -l eng; done

Hope this helps somebody...

Recursively Adding files to CVS

2010-04-20T06:25:00.000-07:00

I'm still running a couple of projects which rely on CVS for version control. But adding more folders recursively is very painful. So I use this line as many times as there still being files/folders to be added.

cvs update -R -P -d | grep "?" | cut -d " " -f 2 | while read line ; do cvs add $line ; done

New boy in town...

2010-04-12T13:30:00.000-07:00

My son (Gustavo) was born last Saturday (April 10th 2010), with 2.790kg (6.15 pounds) and 48cm (1.57 feet).
Here is a picture to share the most amazing moment in my life.

Cool demo on TED

2010-03-10T04:55:00.000-08:00

Hmmm... I am not shy to say I am following Bill Gates on twitter. And he posted a link to Gary Flake talk, in which he demos “pivot”. A very cool tool for info graphics.

Here it is:

More on Open Source Hardware

2010-02-26T13:47:00.000-08:00

Slashdot came with this Retro Arcade-Style Clock, designed by Amanda 'w0z' Wozniak.

MONOCHRON - open source retro clock from adafruit industries on Vimeo.

This toke me the Lady Ada web site with some projects on open source hardware.
http://www.ladyada.net/

Tableau Public

2010-02-11T17:03:00.000-08:00

New tool for interactive data visualization:

http://www.tableausoftware.com/public/

Emacs Regular Expressions

2010-01-28T05:21:00.001-08:00

I do use GNU Emacs for almost every text file related thing. Functions like search, replace, cut, paste, etc are all quickly mastered. But, then I've faced a different situation. I had to replace a string, repeat some numbers and put another string. The answer: regular expressions.

Emacs has a regular expression replace function. To access it, just type: "Ctrl + Alt + Shift + 5" (too much keys huh... ?) And it asks what should be searched. In my case, in which I wanted to capture the regex match, I did type $[0-9][0-9][0-9]$ to locate a 3 digit numbers and capture them. Then I typed enter and did tell Emacs what it should put in those numbers place: ID=\1; mv \1 ./safebox/\1
And enter again and ! to replace all. That is it.

Automation

2010-01-05T02:52:00.000-08:00

As an exercise for our teaching methodologies class, my group had made an automation lecture. Here are a couple of videos illustrating a cool kind of automation.

More on http://xpock.tv/play.php?vid=1823

FTDI USB to Serial

2009-12-28T07:58:00.000-08:00

Hack a Day has exactly the tutorial I am needing: Introduction to FTDI bitbang mode.

It is also a Windows Serial thought USB programming tutorial for dummies.

Reducing Browser Memory Leaks with Google Maps API

2009-12-28T03:55:00.000-08:00

Reducing Browser Memory Leaks

The Google Maps API encourages the use of function closures, and the API event handling system GEvent attaches events to DOM nodes in such a way that almost inevitably causes some browsers to leak memory, particularly Internet Explorer. Version 2 of the Maps API introduces a new method, GUnload(), that will remove most of the circular references that cause these leaks. You should call GUnload() in the onunload event of your page to reduce the potential that your application leaks memory:

 onunload="GUnload()">

Using this function has virtually eliminated Internet Explorer memory leaks in Google Maps, though you should test for memory leaks on your own site using tools like Drip if you are noticing memory consumption problems.

SOURCE: GOOGLE

Internal Projects

2009-12-28T03:02:00.000-08:00

We can't open much about our internal projects here at IDEIA. But now that University students and and professors, our main customers are on vacation, we have more time to spend on some internal projects which were put aside during the year.

One of them, in cooperation with the IDEIA's Optics Lab, is related to digitize images captured with a regular composite video camera. The guy from the Optics Lab have a EasyCAP USB device, which I have to put to work with my linux box.

I didn't find an out of the box solution, or a few steps tutorial to put it to work during the year. Looking again, I've found a couple of forums, tutorials, and links:

http://ubuntuforums.org/showthread.php?t=662531

http://www.unicap-imaging.org/download.htm

http://sourceforge.net/projects/syntekdriver/files/syntekdriver/Release%202.1.0/stk11xx-2.1.0.tar.gz/download

http://ubuntuforums.org/showthread.php?t=451200&highlight=Syntek+Semiconductor

I hope these might be useful to others trying to make this EasyCAP thing work with Linux.

Information Visualization

2009-12-23T03:38:00.000-08:00

Since I had done the visualization class at grad school, the world wans't the same anymore. To look at informational illustrations and graphic plots is being a real cool exercise. And when I have to use some software to plot some chart, quickly come back to my mind when our professor were telling us if we went to his office, he will receive us with a box of paper tissue to wipe our tears away...

So, when I read the slashdot article about a Ronald Knief collecting charts of nuclear reactors, originally published in issues of Nuclear Engineering International, I became very curious.

The Wired website brings more details.

But after reading those articles I had reached the BibliOdissey blog, which has much more digitized illustrations, from artistic illustrations, through info charts, to puzzles. It is really awesome... It has lots of illustrations. They are all hires illustrations, the BibliOdissey has a Flickr gallery with them in 5156 x 3244.

Here are some of my favorites:

Cross-compiling windows applications under linux with wine and DevC++

2009-11-21T14:05:00.000-08:00

This post has the same title as this, from Violin Iliev because it is almost a "repost". I had an old post on compiling win32 binaries on linux, but the technique I had shown lack the windows resource file compiling. Violin had written his wrapper to the windres resource compiler, but one good "emergency option" if one couldn't, or don't want, or hasn't time to, write a wrapper or compile Violin'd wrapper, is to follow what was commented on Violin's blog by someone who signed as Andy. Andy said:

"I had the same problems with windres and mingw32-make under wine 1.0.1
I solved the problems by putting an original copy of msvcrt.dll in the bin subfolder of mingw32 and telling wine to load it first instead of its own msvcrt emulation.
hope it can be useful
Andy"

All my avatars until now

2009-11-12T03:32:00.000-08:00

These are the avatars I use for instant messaging. They were all made with inkscape

Region of interest

2009-11-06T04:17:00.000-08:00

This another test was made with a restricted region of interest, to avoid the detection of undesired squares.

Square detection results:

2009-11-05T04:20:00.001-08:00

This is a first test on my square detection system that will be used for syncing stereo videos.

The centroid of each square is also marked with a red circle, for motion tracking purposes.

Quadrilateral Centroid Algorithm

2009-11-02T16:34:00.000-08:00

Oh men... This time google wasn't helping much...

I was looking for an algorithm to find the centroid from a quadrilateral polygon. It wasn't necessary to be a general, any polygon, centroid algorithm... just one which give me the centroid of a regular convex quadrilateral. It was hard to find something that simple. But finally, here is.
The following code is a C example on how to compute the area and the centroid from a regular convex quadrilateral polygon:

#include<stdio.h>

int main(void){
  float verticesX[5];
  float verticesY[5];
  float centroidX = 0;
  float centroidY = 0;

  verticesX[0] = 3.58; verticesY[0] = 1.90;
  verticesX[1] = 4.48; verticesY[1] = 1.88;
  verticesX[2] = 4.56; verticesY[2] = 2.71;
  verticesX[3] = 3.64; verticesY[3] = 2.74;
  verticesX[4] = 3.58; verticesY[4] = 1.90; // Repeat the first vertex


  int i, k;
  float area = 0.0f;
  float tmp = 0.0f;
  
  for (i = 0; i <= 4; i++){
    k = (i + 1) % (4 + 1);
    tmp = verticesX[i] * verticesY[k] - 
          verticesX[k] * verticesY[i];
    area += tmp;
    centroidX += (verticesX[i] + verticesX[k]) * tmp;
    centroidY += (verticesY[i] + verticesY[k]) * tmp;
  }
  area *= 0.5f;
  centroidX *= 1.0f / (6.0f * area);
  centroidY *= 1.0f / (6.0f * area);
  printf("Centroid = (%1.2f, %1.2f),  area = %1.2f\n", centroidX, centroidY, area);

  return 0;
}

Experiences with OpenCV

2009-10-29T15:39:00.000-07:00

OpenCV has really lots of useful classes and features.
The square detection for my virtual reality class work is being made with it.

Unfortunately, on my tests, I was detecting squares which I didn't want the software to detect. Like on the image below:It would be much better if I could do the image analysis only inside the laptop screen. "Googling" on "OpenCV image crop" I had reached the nashruddin.com (OpenCV Region of Interest - ROI). This blog has a good explanation on how to crop (extract the region of interest) from a image.
With those informations I got the following result for the same frame:

Now I have to check the area of the detected squares. At the web archives of the computer geometry class mailing list, from the Illinois University, google had shown me one algorithm to calculate the area of a closed polygon, as follows:

Let 'vertices' be an array of N pairs (x,y), indexed from 0
Let 'area' = 0.0
for i = 0 to N-1, do
Let j = (i+1) mod N
Let area = area + vertices[i].x * vertices[j].y
Let area = area - vertices[i].y * vertices[j].x
end for

In C, to use with OpenCV:

double polygonArea(CvPoint vertices[]){
  double area = 0.0;
  int i, j;
  for (i=0;i<4;i++){
    j = (i+1) % 4;
    area = area + vertices[i].x * vertices[j].y;
    area = area - vertices[i].y * vertices[j].x;
  }
  if (area<0) area = -area;
  return area;
}

Becoming father...

2009-10-27T13:35:00.000-07:00

After 4 years of marriage we will finally have our first kid.

My wife is writing a blog with more details (in Portuguese). But which is letting me more exited about this near future is the new excuse to buy toys. The chart below from graphjam illustrates well:

see more Funny Graphs

And here is one echo scan image made when we were with 12 weeks of pregnancy:

Developing PlayStation2 Games

2009-10-24T18:48:00.000-07:00

The I finally have a PlayStation2 at home. Now it is time to start looking for tools for game developing for it.

The first place google has shown was http://ps2dev.org/. The first look has been promising. Besides the PlayStation2 related pages, it also has tutorials and articles related to the PlayStation3 and the PSP.

I hope to sooner be posting something about my experiences developing for the PlayStation2.

The results should probably be tested with some PlayStation2 emulator (http://pcsx2.net/, http://www.emulator-zone.com/doc.php/ps2/)

How many times each user has logged in

2009-10-21T05:57:00.000-07:00

Checking auth.log for ssh brute force attacks

2009-10-20T14:34:00.000-07:00

As I am letting my personal computer always on, as a homelinux server, I decided to check if someone is trying to breaking in with SSH brute force attacks.

First I did a grep for fail at the /var/log/auth.log. (grep -i /var/log/auth.log)

And I got lots of lines with the string "fail". With [grep -i /var/log/auth.log | wc -l] I figured out that were 1164 fail entries at auth.log

With an [grep -i fail auth.log | cut -d " " -f 6 | sort | uniq] I checked that were two kind of failed attempts:
Failed
pam_unix(sshd:auth):

So I wrote the following line to check with which users they were attempting to log:
grep Failed auth.log | cut -d " " -f 11 | sort | uniq | while read line ; do echo -n $line" "; grep $line auth.log | wc -l; done | sort -n -k 2

Here, the field position (the number 11 at the above command lines [-f 11]) may change in some systems. At my desktop at work, the username came at the position 9.

Here are the "top ten":
root 2922
user 2884
test 30
oracle 26
admin 22
mythtv 12
user1 6
teste 4
silentios 4
setup 4

Iauch! 2922 attempts! Luckily I always change my SSH config to not permit root logons.

At the /etc/ssh/sshd_config, PermitRootLogin no
And a good habit is to add a last AllowUsers line, followed by the usernames enabled to log trough SSH.

As most unixes do log rotation with gzip, the line above can be changed to zgrep all auth logs as follows:
zgrep Failed auth.log* | cut -d " " -f 11 | sort | uniq | while read line ; do echo -n $line" "; zgrep Failed auth.log* | grep $line | wc -l; done | sort -n -k 2

This particular line took me around 4 minutes running. After that, it came with a list with 676 diferent users which attemped to log with ssh in my host.

Here are the top 50:
w 9707
u 9707
t 9707
sshd 9707
ssh 9707
s 9707
r 9707
p 9707
o 9707
m 9707
log 9707
l 9707
k 9707
i 9707
h 9707
g 9707
f 9707
ed 9707
e 9707
desktop 9707
d 9707
am 9707
a 9707
v 9706
user 9706
n 9706
id 9706
z 8419
c 6818
root 2322
y 840
b 677
j 381
test 319
adm 268
admin 253
at 222
x 189
it 167
q 134
ftp 124
mail 113
web 102
postgres 79
mysql 78
mini 74
suporte 71
guest 67
pop 65
oracle 62

Control and Industrial applications

2009-10-17T19:37:00.000-07:00

http://epics.web.psi.ch/software/ioc-octave/index.php

EPICS at the SLS

EPICS Video Server using Firewire Camera

GNU Octave from PHP without temp files

2009-10-17T19:16:00.000-07:00

Of course... How haven't I thought that? Pipes!

I was "googling" about PHP and Octave and I had found some simple approach at a mailing list archive. I had already used Octave with PHP but I had always used temporary files, but pipes are a much simpler approach.

From the mailing list post:

in php
start "octave -q script" with popen

create a string in php e.g. "input_data = [102 10 10 10 10 10];"

write this string to the pipe

in octave

recive the string with fread on stdin
let the eval function do the job
calculate

print the result with printf in php syntax "$result = array(12,10,9,12,)"

php
read the output from the pipe (with php fread)
use phps eval function


but using eval with octave and php is a security risk, to avid eval parse
the matrix wird scanf

this is also not the fastes way to use octave (the octave startup needs a
lot of time)

Plotting with AJAX + Javascript

2009-10-09T17:12:00.000-07:00

A friend of mine had written an application which communicates with a small microcotroled board and saves data read from this board on a mysql database. He wants to plot these data on the web. He wrote a PHP script using the GD lib. He did a real good job, but he wants it to plot the data dynamically and an http refresh made things a little ugly. He is now trying to plot directly with AJAX + Javascript. He is trying to use Flot, which is a javascrit for plotting data.
Another usefull resource for realtime web graphics is the CavasDemos.

Regex within PostgreSQL

2009-10-05T13:48:00.000-07:00

Regex (Regular expressions) are very useful. I had to make a SQL query to return only the firstname from a table where the field provides the full name.
ideia_onde=# SELECT name FROM users;
name
--------------------------------
Linus Torvalds
Randal Schwartz
Steve Wozniak
(3 rows)

ideia_onde=#
Now, with a simple substring using a regular expression:
SELECT SUBSTRING(name, '(.*?(\\s))') FROM users;
substring
-----------
Linus
Randal
Steve
(3 rows)

ideia_onde=#
What do I did?
The substring function extracts from the name field everything (.*) until (?) a space character (\\s).

Experiences with Tecgraf Libraries

2009-10-03T18:50:00.001-07:00

My advisor is always right. So I have decided to take a look at Im lib, from Tecgraf.

As a learner by example, I first tried to compile and run the examples provided with Im lib, but most of their examples came written in lua and I need to write my code in C (or C++). Fortunately there were 6 examples written in C++:
glut_capture.c im_copy.cpp im_info.cpp im_view.c iupglview.c proc_fourier.cpp
But, I wans't use glut (discarted glut_capture.c and iupglview.c)
So I've choosen im_view.c to try to compile, and the torture has started. There wans't any doc, readme or anything which tells something on how to compile the examples. The only clue was the comments written on the source header:
/*
IM 3 sample that shows an image. Needs "im.lib", "iup.lib", "cd.lib" and "cdiup.lib". Usage: im_view Example: im_view test.tif Click on image to open another file.
*/
Well, I had discovered that I was needing three more libs from Tecgraf to compile this example. So let's get them. With all these four libs I did put them all at /usr/local/tec/include and /usr/local/tec/lib, changed my /etc/ld.so.conf to add /usr/local/tec/lib and had runned the ldconfig command. But now, which GCC parameters I should use?

Issuing a gcc -I/usr/local/tec/include/ -L/usr/local/tec/lib im_view.c
was always resulting on error. Taking a look at imlib dependencies with ldd
# ldd libim.so
linux-gate.so.1 => (0xb7f27000)
libm.so.6 => not found
libgcc_s.so.1 => /lib/libgcc_s.so.1 (0xb7dc9000)
libc.so.6 => /lib/tls/i686/cmov/libc.so.6 (0xb7c79000) /lib/ld-linux.so.2 (0xb7f28000)
I have discovered that my system was missing the libm.so.6. After googling a little I have figured out that libm is the motif library. With a apt-cache search libmotif:
apt-cache search libmotif
libmotif-dev - Open Motif - development files
libmotif3 - Open Motif - shared libraries
Ubuntu has a package for libmotif3. Installing it the ldd on libim.so din'd show bronken dependencies anymore:
# ldd libim.so
linux-gate.so.1 => (0xb7f27000)
libm.so.6 => /lib/tls/i686/cmov/libm.so.6 (0xb7dd4000)
libgcc_s.so.1 => /lib/libgcc_s.so.1 (0xb7dc9000)
libc.so.6 => /lib/tls/i686/cmov/libc.so.6 (0xb7c79000) /lib/ld-linux.so.2 (0xb7f28000)
And adding the -l flag to the gcc, I got this output:
gcc -I/usr/local/tec/include/ -L/usr/local/tec/lib im_view.c -liup -lim -lcd
/tmp/ccKdeRAP.o: In function `CreateDialog': im_view.c:(.text+0x634): undefined reference to `cdContextIup'
/usr/local/tec/lib/libim.so: undefined reference to `operator new[](unsigned int)'
/usr/local/tec/lib/libim.so: undefined reference to `operator delete[](void*)'
/usr/local/tec/lib/libim.so: undefined reference to `operator delete(void*)'
/usr/local/tec/lib/libim.so: undefined reference to `__cxa_pure_virtual'
/usr/local/tec/lib/libim.so: undefined reference to `__gxx_personality_v0'
/usr/local/tec/lib/libim.so: undefined reference to `vtable for __cxxabiv1::__vmi_class_type_info'
/usr/local/tec/lib/libim.so: undefined reference to `vtable for __cxxabiv1::__class_type_info'
/usr/local/tec/lib/libim.so: undefined reference to `operator new(unsigned int)'
/usr/local/tec/lib/libim.so: undefined reference to `vtable for __cxxabiv1::__si_class_type_info'
collect2: ld returned 1 exit status
Very strange, as im_view.c was suposed to be a C program, not C++. Well the libs must have C++ operations, so let's compile with g++.
g++ -I/usr/local/tec/include/ -L/usr/local/tec/lib im_view.c -liup -lim -lcd
/tmp/cc01yIbF.o: In function `CreateDialog()':
im_view.c:(.text+0xd8): undefined reference to `cdContextIup' collect2: ld returned 1 exit status
But there still one missing reference. Obviously I had missed -lcdiup, but:
g++ -I/usr/local/tec/include/ -L/usr/local/tec/lib im_view.c -liup -lim -lcd -lcdiup
/usr/bin/ld: cannot find -lcdiup collect2: ld returned 1 exit status
So what's up.
Fortunately, the project has an on-line history log
http://www.tecgraf.puc-rio.br/cd/en/histor y.html
And looking at the history, I found this peace of information:

Changed: IMPORTANT - the "cdiup" and "cdluaiup" libraries moved from CD to IUP under the name "iupcd" and "iupluacd". But headers and documentation remains on the CD package. Function names were NOT changed. This change eliminates a cross-dependency that IUP and CD had, now only IUP depends on CD.

So, it wasn't -lcdiup, in stead it was -liupcd. I finally had my g++ command line:
g++ -I/usr/local/tec/include/ -L/usr/local/tec/lib im_view.c -liup -lim -lcd -liupcd
And here is a screenshot of my im_view running:

Im lib looks very promising. Now that I have runned my first example, I hope to learn it soon.

Converting a video file to lots of images

2009-10-03T13:19:00.000-07:00

Still for that grad school work on stereo video, I want to convert the videos I made to a bunch of bitmap images.

With linux and ffmpeg it is easy. It is just type:

ffmpeg -i video.dv image%03d.bmp

There are more ffmpeg cheats at:
http://webupd8.blogspot.com/2009/08/ffmpeg-cheat-sheet-19-best-practices.html

Here is a couple of links very useful:

Specifically, the command line I was looking for is:

ffmpeg -i esquerda.dv -f image2 foo_%02d.bmp

Google Bookmarks And Google Notebook

2009-10-01T05:22:00.000-07:00

As an advise from my grad school advisor, I am now putting all references I am reading for my master's thesis on google bookmarks. There also is a short cut to directly add a page on ones bookmarks, using a simple firefox bookmarks toolbar button. The best part, is that with google notebook, another tool, one can share the bookmarks. So my advisor can check what I am reading.

The URL of my public bookmarks is:
https://www.google.com/notebook/public/02836905453520795692/BDT3iIgoQh_GewpYj

Some light at the end of the tunnel! Hope it is not the train!

2009-09-16T10:54:00.001-07:00

Watching a phd presentation this afternoon, I was introduced to two new libraries deal.II and the trilinos project.

EIDORS on geophysics

2009-09-13T15:32:00.000-07:00

http://eidors3d.sourceforge.net/tutorial/other_models/square_mesh.shtml

Relay Method Automates PID Loop Tuning

2009-09-12T18:48:00.001-07:00

http://www.controleng.com/article/339859-Relay_Method_Automates_PID_Loop_Tuning.php

Stereo Video

2009-09-11T21:10:00.000-07:00

Another grad school class work... Stereo Video.

Let's start googling around...

First good impression link: http://stereo.jpn.org/eng/stvmkr/
And this another one: http://www.blender.org/forum/viewtopic.php?highlight=active+stereo&t=9984

Numerical Linear Algebra Packages on Linux

2009-09-11T08:20:00.000-07:00

As a control engineer, I am always needing to use some numerical linear algebra software, usually Matlab or GNU Octave, but now that I have to write some C code using MPI for solving some linear algebra problems.
There are some software packages for that so.

Jochen Voss has a nice tutorial on BLAS and LAPACK at http://seehuhn.de/pages/linear

I was also googling around looking for something on sparse matrix with C. I've found this thread at a forum:
http://forums.aspfree.com/programming-help-33/c-initializing-a-sparse-matrix-236415.html

Mesh generator and Finite Element Solver

2009-08-19T16:52:00.000-07:00

I was reading some papers at Universia, and I've found this one which references the Gmsh, a apparently simple mesh generator with an simple integrated CAD. It also has screencasts showing how to use it.
Gmsh was is developed by the professor Christophe Geuzaine for academic uses. I didn't read much, but Gmsh is apparently scriptable and the CAD tool is realy simple to use. I was planning to develop something very similar. Another cool thing at the professor's site is the project GL2PS, which the main idea, on convert OpenGL rendering in PS, PDF and SVG, I was also thinking in.
Professor Geyzaine had also written an finite element solver, the GetDP.
I am planning to use them all on some grad school works.
Another code on Finite Element Analysis is the SLFFEA, which stands for San Le's Free Finite Element Analysis, deserves note and is entierly written in Ansi C.

Warning against using pie charts

2009-08-18T18:17:00.000-07:00

Bernhard Reiter had wrote a really nice warning against using pie charts, and he did put it on his plotting tool ;-)

Here is a peace:

"... Piecharts are generally not recommended to visualise information! Use bar- or pointchars instead if the quantities are important. Studies have shown that piecharts are hard to read if you actually have to answer questions about the numbers they represent. They look very pleasing and are used in a lot of places but they do not help to visualise information that well. Analytic thing person will read the percentages or values given on the legend or the chart itself and analyse them in their head. ... "

Check the full text at his web site.

Some tricks with gnuplot

2009-08-03T10:39:00.000-07:00

I've been using gnuplot to embed graphics on my scripts for quite some time. And I liked it much.

Last month I was asked to maintain a legacy application which generates some live graphics using the JFreeChart class. It has some transparent animated 3D pie charts. So, I was wondering if I could do the same with a couple of scripts and gnuplot, generating an animated gif.

After googling a little, I've found these links:

And, with these new gnuplot features, I will try to do some cool scripts ;-)

Remember to try this

2009-07-24T07:10:00.000-07:00

http://www.nerdlogger.com/2008/06/transcode-and-stream-dv-to-mpeg4-via.html

Engineer Honoris Causa

2009-07-23T04:14:00.000-07:00

We always think of an engineer as a guy who has a college degree. But, in the case o William Kamkwamba, who build an windmill from scrap in his village on Malawi (Africa) we just got back to what really powers engineering: Inspiration, Motivation, Information and Dedication.
He had the Information available at a library, on how a windmill works, he had the Inspiration to see the windmill would fulfill the necessity of electric power his village had and those factors gave him the Motivation and with Dedication he did accomplish his windmill.

William Kamkwamba spoke at TED

And has a blog now.

This is a good example of a talented engineer.

College degrees give us Information, but if we don't have the Inspiration, Motivation and Dedication, we will never be a real engineer. The College degree also legitimates the engineer but in William's case, his windmill legitimates his engineering skills.