eXTReMe Tracker
Mar 042009
 

In our functional imaging lab we have a poster of Electromagetic radiation spectrum. The chart goes from wavelengths corresponding to millihertz all the way up to EHz which is in 10^18 Hz range. It also describes the kind of systems that use those wavelengths, like for example the 87 to 108 MHz range is used for FM radio broadcasting and so on. I wanted to have that poster for myself so I looked around to see where I can buy one online. I found it on Unihedron website.

EM Radiation Spectrum Chart closeup

EM Radiation Spectrum Chart closeup

The person who created the website has the poster available for download – some of them in PDF and JPG formats. The posters are also on sale on that website, and at least as far as the EM radation spectrum poster goes, its available at quite an affordable price on that website.

There were other posters that were equally interesting, if you are into that kind of things. They were:

  • Value of Pi going up to 350,390 digits.
Poster of Pi: Going up to 350,390 decimals

Poster of Pi: Going up to 350,390 decimals

  • Value of e going up to 350,390 digits.

Poster of e with value going to 350,390 digits

Poster of e: Going up to 350,390 decimals

  • Primes numbers: The first 54,222 prime numbers

Poster with 54,222 primes

Poster with 54,222 primes

These are some great posters, especially the one with EM Radiation. Its a wonderful chart to have for reference if you are dealing with higher frequencies like in telecommunications or in medical imaging.

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Mar 032009
 

I had to create a movie/animation out of a series of images that I had in my folder. There were several methods described on several forums which suggested using GIMP for creating GIF files from JPG or PNG files when one is using Linux. Now the problem was that I had 70 files in total and it would have taken me a long to time to add all those images to GIMP in order to create my animation file.

Then I read somewhere that we can actually create GIF images in command line mode using Imagemagick. But to do so you need to have Imagemagick installed on your system. To install it in Ubuntu, run:

sudo apt-get install imagemagick

This program has several features that would let you do all sorts of things with images. I was interested in converting a bunch of PNG files into an animated GIF file. To do so, we need to¬† rename the files in a way that they would lie in a sequence when arranged alphabetically (if you plan on doing it the easy way). Suppose you have files named slide_01.png, slide_02.png, slide_02.png….slide_xx.png, and you want to convert them to movie.gif, we run:

convert -delay 10 -loop 0 slide*.png movie.gif

The parameter delay inserts a desired delay between two consecutive slides. The number x used for delay inserts 10x milliseconds of delay between two frames. Loop parameter 0 makes it repeat infinitely.

If you had files with non-uniform names, then you need to input each of them in a sequence after the delay and loop parameters. Suppose you have file summer.jpg, fall, winter.jpg, fall.jpg and spring.jpg and you want to order them as fall, winter, spring and summer in the gif image seasons.gif with a 1 second delay between each of them, use:

convert -delay 100 -loop 0 fall.jpg winter.jpg spring.jpg summer.jpg seasons.gif

Here are some animations of numbers from 0 to 9 with varying delays.

The delay values specified the above cases were: 1, 5, 15, 25, 50 and 100.

gif animation with 10 millisecond delay

GIF animation with 10 millisecond frame delay

gif animation with 50 millisecond delay

GIF animation with 50 millisecond frame delay

gif animation with 150 millisecond delay

GIF animation with 150 millisecond frame delay

gif animation with 250 millisecond delay

GIF animation with 250 millisecond frame delay

gif animation with 500 millisecond delay

GIF animation with 500 millisecond frame delay

gif animation 1 second delay

GIF animation 1 second frame delay

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