February 25, 2009

CVprimer primary source on Betti numbers, according to AMS

Filed under: education,mathematics,news,site — Peter Saveliev @ 3:32 pm

When I discovered that Google puts my tiny article at #3 for search of “Betti numbers”  (after Wikipedia and Wolfram MathWorld), I thought “OK, they don’t know anything, this is just an algorithm”. But now my own American Mathematical society links to that article! I must say I am so flattered… I also humbly promise to improve the article.

The page the AMS’s site is on Mathematics Events at the 2009 AAAS Meeting  which, incidentally, has some interesting discussion about applications of topology. That reminds me also that there will be a short course on Applied Algebraic Topology  at IMA in June that some readers of this blog might find interesting.

BTW there wes a huge spike of traffic to the site over the weekend. It was fueled by reddit, Delicious and StumleUpon. Nice too.

February 24, 2009

Books on computer vision, part 4

As I have mentioned before, I am at the initial stages of writing a book on elementary computer vision (see part 1, part 2part 3). The alst one was Computer Vision by Shapiro and Stockman. Now a few thoughts about Computational Homology by Kaczynski, Mischaikow, and Mrozek (Springer, 2004).

Thorough presentation of all the mathematics is given.
  • A solid course in modern algebra is required for the student.
  • Prior experience with algebraic topology is required for the teacher.
Algorithms are presented in pseudocode.
Prior experience with algorithms is required.
Software (CHomP) is provided.
Prior experience with C++ is required.
The homology of n-dimensional images is addressed in full generality.
Not addressed: 

Website contains examples and downloads.
Numerous exercises are provided.
Projects provided online are geared toward academic research.
  The prerequisites make it a graduate course.

February 16, 2009

Object recognition demo from Numenta

Filed under: computer vision/machine vision/AI,image search,rants,reviews — Peter Saveliev @ 6:01 pm

The link to this demo was sent to me by Ricardo Niederberger Cabral (thanks!). The demo program is called Vision4 and was created by Numenta. This is its main point:

This program demonstrates some capabilities of Numenta’s Hierarchical Temporal Memory (HTM) technology applied to visual object recognition. .. The HTM network contained in this demo has been trained to recognize four types of objects: cell phones, sailboats, cows, and rubber ducks.

Every image is given four ratings. Each represents how much the image resembles one of the four types.

As you can see, the goal is modest and there are no unsubstantiated claims of how this is ready to be applied in real life (and don’t get me started on academic publications!). This is refreshing. The program is also fun to play with. You can load your own images, you can add noise, blur etc to the images and see the effect on the recognition. The recognition results are often good and when they aren’t, it’s still interesting.

For serious purposes, it is unclear where this is going though.

It’s fine with me that there are only four categories – just one would be enough to test the concept. It does not bother me when a face is rated high in the cow category and another face high in the duck category. My main complaint is the instability of recognition under image transformations. For example, after turning “sailboat” a few degrees it became “cell phone”. A few degrees more and it becomes mixed - half “cow” (first image below). Adding noise, occlusion, etc has similar effect (second image).

Certainly, one does not expect rotations to affect image recognition. Meanwhile, a mixed recognition is a failed recognition and should be presented as such.

I am certainly biased here. I don’t believe in “build[ing] machines that work on principles used by the brain”. I don’t believe in trying to imitate brain and I’ve written a few times about that. Traditionally, a scientist tries to understand nature by observing it, analyzing it, etc. Instead, it is suggested to try to understand nature by first understanding how the brain understands it? Seems like a roundabout to me, bordering on a vicious circle. I also have serious reservations about the use of machine learning in computer vision.

Annoying bug: every time I start it, the program would turn on my webcam and it would keep it on even after I shut it down.

February 10, 2009

Image search engines keep launching: Milabra

Filed under: computer vision/machine vision/AI,image search,rants,reviews — Peter Saveliev @ 2:26 am

TechCrunch is happy to do PR for another visual search company: Milabra.

Milabra claims that it can categorize images, “from puppies to porn”:

…when searching through a library of images for dogs, Milabra doesn’t need to constantly compare each image with its database of known ‘dog’ images - instead, it can look for traits that it has learned to associate with “doggyness”…

The two examples in the demo are “beach” and “dog”. You upload an image with people on the beach, click “Search” and you get a page of beach photos… Wait, you don’t get to upload anything – this is just a video! So, there is no way to test their claims. Unfortunately, this is not unusual in this area and in computer vision in general.

If your software can recognize a puppy in an image (95% of the time as you claim), it should be easy for you to demonstrate this ability. Create a little web application (or desktop, I don’t care) that allows me to upload my own image which is then identified as “puppy” (or “tree”, or “street”, I don’t care). There is no such program. Why not? The answer is obvious.

In response to some skepticism, this is what one of the founders wrote:

…if you think that this cannot be done, then you are completely clueless: object classifiers have been made for more than 10 years now at leading CS labs around the world.

That reminds me of the episode of Seinfeld when Kramer decides to build levels in his apartment:

KRAMER: It’s a simple job. Why, you don’t think I can?

JERRY: Oh, no. It’s not that I don’t think you can. I know that you can’t, and I’m positive that you won’t.

This is Millabra’s team:

  • MBA
  • MS in Biological Engineering and PhD in neuroscience
  • MS in Computer Science and Ph.D. in Biophysics
  • Professional Project Manager
  • Expert in computer networking, user interface design

JERRY: I don’t see it happening.

And what about TechCrunch? Same story again and again since I started to keep track a couple of years ago: they publish an enthusiastic report about a company doing image analysis/search/recognition, and then silence. The company slips into obscurity and there is no follow-up, nothing. These people never learn…

The people who do seem to learn, slowly, are the investors: Riya (like.com) $20 million or more, Polar Rose $5 million, Milabra $1.4 million. Or maybe this is just the effect of the economic downturn?

February 2, 2009

Pixcavator FAQ

Filed under: image processing/image analysis software,site,updates — Peter Saveliev @ 3:28 pm

FAQ, Frequently Asked Questions

Can you help me analyze these images?

We may be able to provide you with a sample of what Pixcavator can find in your images. For more meaningful results, however, the image should be analyzed by a person who knows that he needs to find in the image. One way to accomplish that is by experimenting with Pixcavator. We can help with that. However, we are unfamiliar with the terminology of your field and can’t tell what you are looking for based solely on your verbal explanations. Ideally, you would provide us with a few images that have been analyzed manually. Then we would try to reproduce your results with our software. Then, if this works, we could try to apply the analysis to other images. For more read the wiki article on technical support.

I am interested in purchasing your software. Since I work for a school I was wondering if you offered an educator’s discount?

There is only one price at this time, except for a free student version here. It has some limitations though…

I am a researcher at .. University. How do you normally handle orders/payment from a large institution?

There is just one way of purchasing at this time - by credit card (or PayPal) - that does not involve contracts, invoices, etc.

Is there any way to utilize Pixcavator from within a Visual Basic application, so I could streamline the process of obtaining the information that we need?

The whole Pixcavator is written in C++ using MS Visual Studio. There is also a way to call a C++ library from a Visual Basic program.

Can I apply a conversion factor to convert area in pixels to area in sq-in, or would I need to do that in Excel afterward?

At this time there is no feature that would convert automatically, so, yes, you’d have to use Excel.

How can I known the total number of pixels for each color in the attached image?

Unfortunately, Pixcavator does not have this feature at this time. The way the current version of Pixcavator analyzes image is channel by channel. A feature similar to what you need is planned for 2009. If you would like to be informed about the latest developments, please sign up for our newsletter here.

What is the runtime fee for the library? Is it $150?

Pixcavator itself costs $150. The price of the library highly depends on how you use it and other circumstances. You can try the free version described here.

I’m trying to transfer my copy of Pixcavator to my new machine. However, during activation I get an error that the maximum number of activations is reached. Is there anything that you can do about this?

We encounter installation issues once in a while. They are usually quickly settled. Activation, however, is taken care entirely by Protexis. Please visit their support site.

Can I get a refund for Pixcavator?

Yes, within 30 days. You will have to contact us first then the refund will be processed by Protexis as the seller of record.

I can’t copy Pixcavator to another computer. Is Pixcavator a single-try demo version?

No, but it is licensed to one computer at a time. You should just reactivate it.