Simple Gaussian Blur in MatLab

One of my first graduate courses at Iowa State in the Human Computer Interaction field is ME 556X: Machine Vision. This is my first course of this kind and the first of which to deal with image processing. 

I’ve been progressing through my book and taking note of the examples presented in class, and I’d like to share one such example: the gaussian image blur!

Now, this blur can be useful for eliminating certain types of image noise (especially when the noise is of varying intensity, not merely black and white). The effect can also be applied to images that you’d just like to apply a nice blur effect to! 

The idea of the filter is to apply a natural—in the sense of optics—blur to each pixel (and its surrounding pixels) in the image. The intensity of the blur is easily altered programmatically by simply changing the

"Sig = ...;"

value (see code sample below); the lower it gets, the more dramatic the blur effect. 

In the above image, the Sig value is equal to 50.

Now, in this image above, the Sig value is set to 5. You can see how much more dramatic the Gaussian blur is. 

…

Want to try it out for yourself? Paste the code below into a MatLab script and grab the below image:

close all;
clear all;

I = imread ('lena.png');
subplot(1,2,1);
imshow (I);

I1 = fft2 (I);
I2 = fftshift (I1);

[w, h] = size (I);
GF = zeros ([w, h]);

% This value determines the 'blur' amount:
% The higher it goes, the less the blur is;
% The lower it goes, the more blur there is.
Sig = 5;

for x = 1 : w
    for y = 1 : h
        GF (x, y) = exp (-((x-w/2)^2 + (y-h/2)^2) / (2 * Sig^2));
    end
end

I3 = I2 .* GF;
I4 = ifft2 (fftshift (I3));

subplot(1,2,2);
imshow(abs(I4)/255);

Have fun!

Farewell, AT&T

We’ve had a good run, AT&T, but I’m afraid our time is through. It’s not me, it’s you. Ever since 2008, I’ve been a loyal customer of yours. I told everyone that your service wasn’t terrible and that getting an iPhone was worth it, even if they had to get you alongside it.

Even when I was tempted with other options, I stuck by your side. And you stuck by mine, allowing me to keep my unlimited data plan. It is, ironically, what you have done with that unlimited plan that is why I am leaving you.

You see, I am sick of being throttled and am sick of the alerts telling me that I am using too much of my unlimited data. And I sure as hell don’t want to pay for FaceTime over a cellular network. It’s a new feature in iOS6, why prohibit its growth and how many people will be able to use it?

I haven’t changed, AT&T, you have. And that is why, come Friday, my number will be switching to Verizon. I hope Verizon takes better care of me and appreciates my service. We’ve had our good times, but now, that’s all they are.

Do well for yourself, AT&T, and don’t lose hope. Maybe if you clean up your act, we can be friends again someday.

Sincerely,

Tyler Bell

My Fall 2012 Semester @ Iowa State

The Fall 2012 semester has begun! This will be my last semester as a computer science undergraduate here at Iowa State, as I will be graduating in December. The last two years have gone by rather quickly, and I’ve grown not only as a developer but as a person.

From a computer science perspective, my courses this semester are simply awesome and coincide with many of my interests.

My CS Courses:
CS352 — Introduction to Operating Systems
CS331 — Theory of Computing
CS472 — Principles of Artificial Intelligence
CS477 — Problem Solving Techniques for Applied Computer Science

Electives:
ENGL335 — Studies in Film
DANCE160 — Ballroom Dance I

As I come into relevant projects in my CS courses, they will most likely be mentioned on this blog.

Keep your eyes open!

On My Bookshelf, August 2012

With the new semester rapidly approaching, I have moved back in to my apartment. During the move-in I reorganized my bookshelf, and I thought I’d share what it contains at the start of the Fall 2012 semester.

The shelf features a decent selection (mostly technical reference books, though). Any book that I recommend or that I am currently reading will be underlined with a link for your further investigation.

Read More

Don’t Buy Another Stylus

“God gave us ten styluses … Let’s not invent another.” — Steve Jobs

Let’s face it, Steve Jobs was right, using your finger to interact with the touch interface of an iOS device is intuitive and extremely easy to do. In most cases.

A counter-example: I take my iPad to almost every lecture with me and use it to annotate my PDF textbooks, write down assignments, and take hand-written notes. Use cases such as these is where the finger begins to fail in regards to the touch interface, especially with larger fingers such as mine.

To solve this issue in the past, I have purchased styluses from different retailers, and these have usually gotten the job done. The stylus isn’t used as my primary interaction device, but comes out when something needs to be written, drawn, or sketched.

Rubber-tipped styluses, however, have a tendency to wear out: the tip begins to turn soft and can even tear in places. The cost of replacing a stylus isn’t much (usually $15 for a decent pen), but that can quickly add up.

My new solution? Creating one for myself. A few years ago I watched a tutorial on how to make your own stylus, but I could never come across all of the appropriate materials to MacGyver myself a workable pen. If you can find the materials, here’s what you’ll need to make your own:

• Empty ball-point pen casing
• Copper wiring
• (Electrical) tape
• Conductive foam

The material that always eluded me was the conductive foam, but I was lucky enough to randomly come into some at my internship this last summer. Creating a stylus, once you have the basic materials, is extremely easy to do. It saves money and is a fun, hands-on chance to create something practical.

The first stylus I made:

The second one I made got a little cleaner:

Follow this tutorial to see how it’s done:

If you end up creating one of your own, send me a picture of it, I’d love to see your creation!