The World of Chakravarthy Bhagvati
The World of Chakravarthy Bhagvati
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Office: E-207, AI Lab
I am a professor in the School of Computer and Information Sciences at University of Hyderabad. My research interests are
  • Colour Image Processing, Pattern Recognition
  • Document Analysis and Research and
  • Deep Learning

I have another set of interests (or vices) in Number Theory, Cryptanalysis and Programming.

Apart from these professional interests, I am also an amateur astronomer, model railroad enthusiast (now you know what happens during vacations!), cruciverbalist (go look it up on Google or whatever!) and ... oh yes, intermediate level player, armchair critic and follower of many sports including cricket, tennis, badminton and golf.

There is also a need somewhere to fit in PGW, Agatha Christie, Asterix, Sherlock Holmes, Shaun the Sheep, Mr. Bean, Looney Tunes, etc. Finally, I need to account for time spent on Carnatic music and Classic Rock - days sure fly by swiftly.

Rensselaer Polytechnic Institute
M. Tech(CS)
University of Hyderabad
B. Tech(ECE)
JNTU College of Engineering


Telugu (తెలుగు) Optical Character Recognition:
An Optical Character Recognition (OCR) system converts document images into text (either in ASCII or Unicode formats). OCR systems generally have a preprocessing stage for cleaning input document images and segmenting them into lines, words and characters while separating out graphical and other non-text elements. The text elements are passed to a classifier which labels them for output in text format. Our classifier is a 5-layer convolutional neural network trained on about 70,000 labelled and 200,000 unlabelled samples.
We have a complete end-to-end OCR system for Telugu script in our lab. It has been tested on a 4000 page third-party corpus and gives an accuracy greater than 91%. Most of the errors occur due to preprocessing, especially incorrect segmentation of characters. When the characters are correctly segmented, the accuracy is greater than 96%.

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Colour Image Processing:
Colour images are not, repeat not three times grayscale images. Colour is much more interesting and fascinating with strong links between physics, human vision system and digital spaces and models.

In our lab, we do research on colour science exploring links between spectra and colour operations, developing new colour operations with strong links to physical processes, use of colour in image forensics, and use of human vision principles to improve performance of deep networks.

There is also a Masters level course on Colour Image Processing offered as an elective during January-May semester.

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Deep Learning:
If you are a Pattern Recognition or an Image Processing guy, well, what else can you do these days? Like it or not, deep learning is the rage and I am not immune to it.

My interests lie in using deep learning to study cognitive processes (at least, informally), work on theories behind deep learning by looking at stochastic processes and, finally, in applying deep networks to various day-to-day tasks and have some fun!

We have several students working on deep networks in OCR, video processing, geometry and computer vision tasks, k-shot, one-shot and zero-shot learning, etc. Input domains are primarily visual and text with a smattering of speech.

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Hooked to astronomy from the time I was eight years old or so. Astronomy gave me one of my happiest moments as also one of the greatest disappointments. I saw an occultation of Saturn by the Moon in the year 2000 (I think!): an absolutely breath-taking and awe-inspiring sight to see 'tiny' Saturn emerge from behind a 'giant' Moon. Talk about a live and natural lesson in perspective and 3-D geometry! I cannot forget the sight - it is too emotional, even now gives goosebumps to think about it.

I was in Intermediate first year when the biggest disappointment (in hindsight!) of missing a total solar eclipse happened; on 16 February 1980. The eclipse was 99.5% in Vidyanagar, Hyderabad and was total from any place about 4 km south, and I didn't go - how was I to know that a Solar Eclipse is the grandest celestial spectacle and that the next one in Hyderabad is scheduled only for 18 September 2248! Although, at that time, I must admit, even 99.5% was was quite spectacular - we even had shadow bands scurry across the ground and could see the darkened cone race across the south-eastern sky.

M42 - The Great Nebula in Orion
(06 Feb 2016)

Click on any picture to get a full resolution version.

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Astrophotography ...

... is hard! You need the right equipment: a solid tripod, a good DSLR with settings for time or bulb exposures and a motor drive to track the sky.

My equipment: a 12-yr old Canon point-and-shoot camera, a Celestron 8-inch and a not-so-good tripod. Add light-pollution in Hyderabad and things become quite tricky, to say the least.

All photos here use afocal method where the camera shoots through the eyepiece: usually 12.5mm or 25mm. Exposures are less than 10s.


Orion - The Hunter

The most recognisable constellation of all! Visible from almost anywhere on the Earth, it is also a pointer to many other constellations for a beginner.


Saturn - Lord of the Rings

One of my first attempts at photographing Saturn. You don't know how tough it is until you try it! There is room for improvement.



The largest planet in the solar system is still a small target in telescopes. The real difficulty is in achieving the right focus. At least, the classic cloud bands are in full view.

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Almost Full Moon

Almost Full Moon

Taken about 2 days before the full moon, it shows almost all the principal features on the Moon. The bright crater at the bottom is Kepler and the small bright spot near the left-centre is Aristarchus: one of the brightest regions on the Moon.

Mare Imbrium

Mare Imbrium (Sea of Showers) region with the crater Copernicus on the left. One of my favourites on the Moon because of the variety of features. The almost circular mountain range is punctuated by the prominent crater Plato (on the right).

Mare Imbrium

Copernicus (Close up)

The crater Copernicus, best visible near the first and third quarter phases, is the most prominent feature on the Moon. It is an impact crater with several rings of mountains and also a central peak.

Eclipsed Moon

Copper coloured Moon during the total lunar eclipse of January 2018. The copper colour is due to refraction of the longer wavelengths of light by the Earth's atmosphere.

Eclipsed Moon
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Rare and Interesting Events

Astronomy provides a wonderful field to enjoy rarities. Some of these are eclipses, transits, occultations and conjunctions. Partial Solar Eclipse
Partial Solar Eclipse
15 January 2010

Jupiter Mars Conjunction

Jupiter and Mars

For one day, 6 January 2018, Jupiter had a new satellite: Mars! The red planet was only 0.1 degree from Jupiter. In this photo, the bump on Jupiter is Io, then Europa and Ganymede and the farthest, Callisto.

Venus Saturn Conjunction

Venus and Saturn

A close encounter between Venus and Saturn - thanks to projection effects of 3D to 2D. 9 January 2016, early morning saw Venus and Saturn separated by less than 0.1 degree.

Venus Transit

Transit of Venus

Now, this is rare! Occurs twice eight years apart every 121 years and 106 years. Venus (the large circle at the bottom left) passes right in front of the Sun as seen from the Earth. Photo taken on 6 June 2012 - the last transit for this century!

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These are some of the tools developed over the years for simplifying my own work but may be useful to others too. Some are serious others are for fun.
  • Pradarsana: A set of LaTeX macros for making technical presentations; something on the lines of Beamer but with a different philosophy. Pradarsana works on xelatex.
  • Spiro-designer: a Tcl/Tk based fun program that is based on Spirograph. Lets you draw beautiful patterns and then save them in PostScript format for printing. No manual, though! Try and learn it - if you know Spirograph toy, then spiro-designer is easy, otherwise your mileage may vary.

    Save the file spiro-designer. If Tcl/Tk is properly installed, you can run it by typing either wish -f spiro-designer or ./spiro-designer.

  • Tangrams: The classic chinese puzzle in its modern avatar. One of the first Tcl/Tk projects I did (back in 1997 or so). Again, no manual, but easy to figure out! Of course, you need to have Tcl/Tk installed - check if "wish" command exists.