Wednesday, August 17, 2011

OpenCV performance tests

This is a good article comparing the performance of common tasks on different versions of OpenCV. Newer version doesn't necessarily mean that it is better in performance.



Here is another link that talks about comparison of OpenCV with other programming frameworks.

Sunday, August 14, 2011

A Simple Read/Write Example using Cassandra and Java

In this post, we take a look at basic CRUD (Create Read Update Delete) operations on Cassandra database using Java JDBC.

We only use Eclipse IDE. This example was tested in Windows 7 Operating System.

To find out more about NoSQL databases, look here.

Cassandra is an open source distributed database management system developed by Apache Software Foundation. It was designed to handle very large amounts of data spread out across many commodity servers while providing a highly available service with no single point of failure.
Popular user of Cassandra is Facebook

To find out more on Cassandra, refer its home site here.

  • Download and Install Cassandra from here.
  • Extract the files.
  • Setup the following Environment Variables.
    • JAVA_HOME (Give the link to the jre folder where java is installed)
    • CASSANDRA_HOME (Give the link to the cassandra folder where the files are extracted)
  • Go to the location where you extracted and then into the "~/apache-cassandra-0.6.6/bin" folder and open 'cassandra-cli.bat' file using any text editor
  • Replace Line 21 "if NOT DEFINED CASSANDRA_HOME set CASSANDRA_HOME=%CD%" with "if NOT DEFINED CASSANDRA_HOME set CASSANDRA_HOME=%~dp0.."
    Now save the file after editing the line.
  • Now open the command prompt and goto "~/apache-cassandra-0.6.6/bin>" folder and type the following command '.\cassandra.bat'. This starts the server.
  • Now open another command prompt and goto "~/apache-cassandra-0.6.6/bin>" folder and run '.\cassandra-cli.bat'. This is the UI for the database
  • Connect to the server by typing the command 'connect localhost/9160'.
  • Here, type "Create Keyspace AuthDB ;" This creates a cluster (i.e., database)
  • Here, type "Create Column Family AuthCollection ;" This creates a column family (i.e., table)
  • There are certain jar files needed which are available in the Project Dump which is available for download below. It is present in the folder titled 'JarFiles' in the Project Directory.
  • Be sure to add these jar files to the class path.


The code which performs all the CRUD operations is as follows.


The screen shot of the output is as follows:


This code is available for download along with the entire project directory here.

Wednesday, August 3, 2011

OpenCV ROS tutorial

I recently realized that OpenCV tutorials at ROS website is more useful than any others available out there.

Btw, My other programs in OpenCV will be posted here.

You can download it and other related stuff (cheatsheet, etc) at
  1. https://code.ros.org/trac/opencv/browser/trunk/opencv/doc
  2. https://code.ros.org/trac/opencv/browser/trunk/opencv/doc/opencv_user.pdf

Tuesday, August 2, 2011

Computer Vision research at Google: papers at CVPR 2011

The following are the links to Google's contribution to Computer Vision at CVPR 2011.

http://googleresearch.blogspot.com/2011/06/google-at-cvpr-2011.html

Also its not fair to ignore Microsoft's contribution to Vision Research in CVPR 2011. Microsoft has got about about 20 papers including one of the best papers.

Check this out:

http://www.cvpapers.com/cvpr2011.html