Saturday, April 30, 2011

How I wrote [java]code to give Pencil Sketch effect to a picture

I am creating an application where I wanted to transform images to give them pencil sketch effect which can be easily obtained by photoshop as is described here.

However, I needed to automate the whole process in the code and certainly it is beyond me to look "inside" photoshop to see how it works(what are the algorithms/transformations etc and their implementations).

Anyway, from the article above it became clear that pseudocode looks like following:

s = Read-File-Into-Image("/path/to/image")
g = Convert-To-Gray-Scale(s)
i = Invert-Colors(g)
b = Apply-Gaussian-Blur(i)
result = Color-Dodge-Blend-Merge(b,g)

Now it was a matter of finding open source image-processing library that provided the operations I needed. By googling, I landed on JH Labs. They, freely, provide an image editor on which I tried to replicate the process described in photoshop article mentioned above and indeed I got the pencil sketch effect. Now, the best part is that image processing library behind JH Labs image editor is open source.

Then it was just a matter of coding the pseudocode using the JH labs library and here it is...

BufferedImage src = null;
BufferedImage target = null;
src = File("C:\\tmp\\ss.png"));
src = ImageUtils.convertImageToARGB(src);

//transformations begin=============
//gray scale
PointFilter grayScaleFilter = new GrayscaleFilter();
BufferedImage grayScale = new BufferedImage(src.getWidth(),src.getHeight(),src.getType());
grayScaleFilter.filter(src, grayScale);

//inverted gray scale
BufferedImage inverted = new BufferedImage(src.getWidth(),src.getHeight(),src.getType());
PointFilter invertFilter = new InvertFilter();

//gaussian blurr
GaussianFilter gaussianFilter = new GaussianFilter(20);
BufferedImage gaussianFiltered = new BufferedImage(src.getWidth(),src.getHeight(),src.getType());
gaussianFilter.filter(inverted, gaussianFiltered);

//color dodge
ColorDodgeComposite cdc = new ColorDodgeComposite(1.0f);
CompositeContext cc = cdc.createContext(inverted.getColorModel(), grayScale.getColorModel(), null);
Raster invertedR = gaussianFiltered.getRaster();
Raster grayScaleR = grayScale.getRaster();
BufferedImage composite = new BufferedImage(src.getWidth(),src.getHeight(),src.getType());
WritableRaster colorDodgedR = composite.getRaster();
cc.compose(invertedR, grayScaleR , colorDodgedR);

target = composite;
File outputfile = new File("C:\\tmp\\saved.png");
ImageIO.write(target, "png", outputfile);

Here is how the image transform when I apply above code...

- I used above code on png images. JH Labs code only works with TYPE_INT_ARGB(ref) images so you might need to transform them correctly.
- Code shown above was written to just check the concept and has no regards for performance, beauty.

Well, to be honest, from being a alien to image-processing to getting to the code was not as linear a process as described in this post and I had to do a lot of hit n trial to get to this point. I want to thank Jerry who patiently answered my queries.

Monday, April 18, 2011

How I revised Calculus

I have been following some stuff on machine learning and realized that over time I have forgotten some of the calculus stuff that I learned in college.

I mostly remembered single variable differentiation, integration, maxima/minima etc but could not recollect the precise meaning of limit, continuity, series convergence and also the taylor series and multivariable calculus stuff(partial derivatives, optimization of multivariable function, lagrange multipliers etc).

This note is the shortcut that I took to quickly recap all of the above.

First, I read following( relevant) chapters/sections from the Calculus book by Professor Gilbert Strang.

Section 2.6(Limits) and 2.7(Continuous Functions)
Chapter 10 (Infinite Series)
Chapter 11 (Vectors and Matrices)
Chapter 13 (Partial Derivatives)

I must say that the book is great and covers a lot of breadth maintaining enough depth. However, I could not fully grasp the contents of Chapter-13(Partial Derivatives), probably because of the 3d diagrams on 2d paper(or maybe I just could not pay enough attention).
In order to understand this chapter I followed all the video lectures on Partial Derivatives(Lecture-8 to Lecture-14) from MIT Multivariable calculus course. The video lectures are easier to follow and also explains diagrams done in applets which are much easier to understand. Also, the lecture notes give a very good summary of stuff covered in the lecture videos.

Wednesday, April 13, 2011

embedding activemq in jboss

Today, I worked on a prototype web application that utilized JMS. We decided to use ActiveMQ for this. Here are the things I had to do to get it running embedded inside Jboss.

First, I followed the process described in the doc "Integrating ActiveMQ with Jboss".

By default ActiveMQ uses KahaDB for persistence, but I wanted to use our oracle db infrastructure for this. A bit of googling got me to Introduction to ActiveMQ persistence and that led to JDBC data source configuration . By now I got the ActiveMQ successfully embedded in Jboss and running.

Next, Instead of giving all the oracle db info in the broker-config.xml, I wanted to get it from Jboss managed jdbc datasource(which is being used by other applications also). So, I have already got mydatasource-ds.xml deployed inside deploy/ folder of jboss which looks like following


In order to use above datasource, Here is what I had to put inside activemq-ra.rar/broker-config.xml file.

<beans ...>

<!-- shutdown hook is disabled as RAR classloader may be gone at shutdown -->
<broker xmlns="" useJmx="true" useShutdownHook="false" brokerName="">
<!-- kahaDB directory="activemq-data/kahadb"/ -->
<!--kahaDB directory="${}/activemq"/ -->


<bean id="oracle-ds" class="org.springframework.jndi.JndiObjectFactoryBean">
<property name="jndiName" value="java:jdbc/mydatasource-ds"></property>

Well, above did not work. What happened was that Jboss was trying to start ActiveMQ before deploying mydatasource-ds.xml which resulted in JNDI NameNotFoundException(as java:/jdbc/mydatasource-ds is not available until mydatasource-ds.xml gets deployed). So, in ActiveMQ configuration, I had to declare dependency on mydatasource-ds(so that it gets deployed first). To do it, I created a file named jboss-dependency.xml inside activemq-ra.rar/META-INF/ and pasted following on it.

<dependency xmlns="urn:jboss:dependency:1.0">
<item whenRequired="Real">jboss.jca:service=DataSourceBinding,name=jdbc/mydatasource-ds</item>

Now, We are good :).

BTW, above is by no means an exhaustive list because as we go, we will make a lot of changes for the actual setup but above should get a new person started with less amount of trouble than I had.

Thursday, April 7, 2011

konsole for windows

I am a person who loves to use linux for the bash shell, very very useful command line utilities and a myriad of other useful open source softwares(just one yum install .. away). But, for various constraints, my laptop at work has to have windows. First thing I do to fill the gap is to install cygwin, add it's bin/ folder to the PATH variable and install windows version of all the other open source softwares that I regularly use on linux.

This gets me very close except the cygwin terminal ui feel/experience is nowhere close to kde konsole. Also I have missed the multiple tabs feature of konsole for a long time. I never found a direct alternative of konsole in windows. Though there is one project, kde for windows, in progress which should bring the kde konsole port to windows.

But you don't have to wait any longer to get a konsole-like experience on windows. You should install console that has many konsole like features along with multiple tabs. Once you have installed it, open it and in the menu, go to Edit -> Settings. This opens the console settings window. Then give the path to bash exe from your cygwin installation. Also, click on Hotkeys settings link in the left column and change various key bindings to your liking to get an experience as close to konsole as you like.

Here is how the settings window looks like...

And, finally, here is my konsole for windows...

[Update: April 15'11] If you want to bind "clear" to clear the screen instead of using Ctrl-l for same then you need to create \$HOME/.inputrc file and save following on it.
"clear\r": '\C-l'