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• Using Nearest Neighbour Algorithm for image pattern recognition

  - by user293895

  So I want to be able to recognise patterns in images (such as a number 4), I have been reading about different algorithms and I would really like to use the Nearest Neighbour algorithm, it looks simple and I do understand it based on this tutorial: http://people.revoledu.com/kardi/tutorial/KNN/KNN_Numerical-example.html Problem is, although I understand how to use it to fill in missing data sets, I don't understand how I could use it as a pattern recognition tool to aim in Image Shape Recognition. Could someone please shed some light as to how this algorithm could work for pattern recognition? I have seen tutorials using OpenCV, however I don't really want to use this library as I have the ability to do the pre-processing myself, and it seems silly that I would implement this library just for what should be a simple nearest neighbour algorithm.

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• Implementation of ECC in Java

  - by Rookie_22

  While trying to encrypt a given input using Elliptic Curve Cryptography in Java I'm using the following algorithms for generating the cipher and the key: KeyPairGenerator g = KeyPairGenerator.getInstance("ECDSA"); Cipher cipher = Cipher.getInstance("ECIES"); Now as expected, the cipher isn't accepting the keys generated by the ECDSA algorithm. I get the error as - must be passed IE key. I searched for the ciphers being supported by these 2 methods here: http://java.sun.com/javase/6/docs/technotes/guides/security/StandardNames.html#Cipher Unfortunately no else algo is supported for ECC. Has anyone used ECC generated keys to encrypt/decrypt an input? Which algo should I use for both so that they don't clash with each other?

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• image focus calculation

  - by Oren Mazor

  Hi folks, I'm trying to develop an image focusing algorithm for some test automation work. I've chosen to use AForge.net, since it seems like a nice mature .net friendly system. Unfortunately, I can't seem to find information on building autofocus algorithms from scratch, so I've given it my best try: take image. apply sobel edge detection filter, which generates a greyscale edge outline. generate a histogram and save the standard dev. move camera one step closer to subject and take another picture. if the standard dev is smaller than previous one, we're getting more in focus. otherwise, we've past the optimal distance to be taking pictures. is there a better way? update: HUGE flaw in this, by the way. as I get past the optimal focus point, my "image in focus" value continues growing. you'd expect a parabolic-ish function looking at distance/focus-value, but in reality you get something that's more logarithmic

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• Robotics Simulator

  - by Arkapravo

  Which is the best robotics simulator ? Player Project (simulator + control interface) Microsoft Robotics Studio (simulator + control interface) KiKS (in Matlab, only for Khepera) MobotSim (for point like robots ) ROS (I have only heard about it) URBI (also, only heard about it) Any other As of now, I am just looking to get simple simulations of Potential Field method, Bug Algorithms, A* Algorithm etc ! This article gives a number of such softwares etc, however I was looking for a first hand view from fellow stackoverflowers. Anyone who has worked with any other software etc is most welcome to share his/her experience !

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• Image scaling in C

  - by Ganesh

  Hi, I am designing a jpeg to bmp decoder which scales the image. I have been supplied with the source code for the decoder so my actual work is to design a scaler . I do not know where to begin. I have scouted the internet for the various scaling algorithms but am not sure where to introduce the scaling. So should I do the the scaling after the image is converted into bmp or should I do this during the decoding at the MCU level. am confused :( If you guys have some information to help me out, its appreciated. any material to read, source code to analyse etc....

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• How to specify behavior of Java BufferedImage resize: need min for pixel rows instead of averaging

  - by tucuxi

  I would like to resize a Java BufferedImage, making it smaller vertically but without using any type of averaging, so that if a pixel-row is "blank" (white) in the source image, there will be a white pixel-row in the corresponding position of the destination image: the "min" operation. The default algorithms (specified in getScaledInstance) do not allow me a fine-grained enough control. I would like to implement the following logic: for each pixel row in the w-pixels wide destination image, d = pixel[w] find the corresponding j pixel rows of the source image, s[][] = pixel[j][w] write the new line of pixels, so that d[i] = min(s[j][i]) over all j, i I have been reading on RescaleOp, but have not figured out how to implement this functionality -- it is admittedly a weird type of scaling. Can anyone provide me pointers on how to do this? In the worse case, I figure I can just reserve the destination ImageBuffer and copy the pixels following the pseudocode, but I was wondering if there is better way.

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• Datamining on a mysql database

  - by sliptix

  Hello, I Begin with textmining. I have two database tables with thousands of data.. a table for "skills" and a table for "skills categories" every "skill" belongs to a skills categorie. a "skill" is , physicaly, a varchar(200) field in the database, where there is some text describing the skill. Here are some skills extracted from the skills table: "PHP (good level), Java (intermediaite), C++" "PHP5" "project management and quality management" "begining Javascript" "water engineering" "dfsdf zerze rzer" "cibling customers" what i want to do is to extract knowledge from those fields, i mean extract only the real skill and ignore the rest of useless text. for the above example i want to get only an array with: "PHP" "Java" "C++" "PHP5" "project management" "quality management" "Javascript" "water engineering" "cibling customers" what should i do to extract the skills from tons of data please ? do you know specific algorithms to do this ? ex : k-means ... ? Thanks in advance.

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• How to setup matlab for parallel processing on Amazon EC2?

  - by JohnIdol

  I just setup a Extra Large Heavy Computation EC2 instance to throw it at my Genetic Algorithms problem, hoping to speed up things. This instance has 8 Intel Xeon processors (around 2.4Ghz each) and 7 Gigs of RAM. On my machine I have an Intel Core Duo, and matlab is able to work with my two cores just fine. On the EC2 instance though, matlab only is capable of detecting 1 out of 8 processors. Obviously the difference is that I have my 2 cores on a single processor, while the EC2 instance has 8 distinct processors. My question is, how do I get matlab to work with those 8 processors? I found this paper, but it seems related to setting up matlab with multiple EC2 instances, which is not my problem. Any help appreciated!

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• Calculating determinant by hand

  - by ldigas

  Okey, this is only half programming, but let's see how you are on terms with manual calculations. I believe many of you did this on your university's while giving "linear systems" ... the problem is it's been so long I can't remember how to do it any more. I know quite a few algorithms for calculating determinants, and they all work fine ... for large systems, where one would never try to do it manually. Unfortunatelly, I'm soon going on an exam, where I do have to calculate it manually, up to the system of 5. So, I have a K(omega) matrix that looks like this: [2-(omega^2)*c -4 2 0 0] [-2 5-(omega^2)*c -4 1 0] [1 -4 6-(omega^2)*c -4 1] [0 1 -4 5-(omega^2)*c -2] [0 0 2 -4 2-(omega^2)*c] and I need all the omegas which satisfy the det[K(omega)]=0 criteria. What would be a good way to calculate it so it can be repeated in a manual process ?

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• Java Concurrency: CAS vs Locking

  - by Hugo Walker

  Im currently reading the Book Java Concurrency in Practice. In the Chapter 15 they are speaking about the Nonblocking algorithms and the compare-and-swap (CAS) Method. It is written that the CAS perform much better than the Locking Methods. I want to ask the people which already worked with both of this concepts and would like to hear when you are preferring which of these concept? Is it really so much faster? Personally for me the usage of Locks is much clearer and easier to understand and maybe even better to maintain. (Please correct me if I am wrong). Should we really focus creating our concurrent code related on CAS than Locks to get a better performance boost or is sustainability a higher thing? I know there is maybe not a strict rule, when to use what. But I just would like to hear some opinions, experiences with the new concept of CAS.

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• How to generate a unique hash for a URL ?

  - by Jacques René Mesrine

  Given these two images from twitter. http://a3.twimg.com/profile_images/130500759/lowres_profilepic.jpg http://a1.twimg.com/profile_images/58079916/lowres_profilepic.jpg I want to download them to local filesystem & store them in a single directory. How shall I overcome name conflicts ? In the example above, I cannot store them as *lowres_profilepic.jpg*. My design idea is treat the URLs as opaque strings except for the last segment. What algorithms (implemented as f) can I use to hash the prefixes into unique strings. f( "http://a3.twimg.com/profile_images/130500759/" ) = 6tgjsdjfjdhgf f( "http://a1.twimg.com/profile_images/58079916/" ) = iuhd87ysdfhdk That way, I can save the files as:- 6tgjsdjfjdhgf_lowres_profilepic.jpg iuhd87ysdfhdk_lowres_profilepic.jpg I don't want a cryptographic algorithm as it this needs to be a performant operation.

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• Storing and comparing biometric information

  - by Chathuranga Chandrasekara

  I am not sure whether this is the best place to post this. But this is strongly related with programming so decided to put this here. In general we use biometrics in computer applications say for authentication. Lets get 2 examples finger prints and facial recognition. In those cases how we keep the information for comparison. As an example we can't keep a image and process it every time. So what are the methodologies we use to store/determine the similarity in such cases? Are there any special algorithms that designed for that purposes.? (Ex : To return a approximately equal value for a finger print of a certain person every time)

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• which is best algorithm?

  - by Lopa

  Consider two algorithms A and B which solve the same problem, and have time complexities (in terms of the number of elementary operations they perform) given respectively by a(n) = 9n+6 b(n) = 2(n^2)+1 (i) Which algorithm is the best asymptotically? (ii) Which is the best for small input sizes n, and for what values of n is this the case? (You may assume where necessary that n0.) i think its 9n+6. guys could you please help me with whether its right or wrong?? and whats the answer for part b. what exactly do they want?

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• Resources to learn sh scripting 'just like a normal programming language'

  - by Homer J. Simpson

  Hi, what is the best resource (book would be nice) to learn sh scripting (the "standard" shell on Unix systems) just like when i would learn a "normal" programming/scripting language ? There are lots of tutorials on certain aspects of shell scripting, they mostly deal with shells in general and unix commands and so on, but i would rather like to find a more general approach - meaning a quick syntactic overview and an outlook on how to do things you normally do when programming, like implementing small algorithms and so on. Doing actual scripting, not just a structured batch file. And rather 100-liners than 1-to-3-liners. Can you recommend a good standard book on the topic ?

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• Efficient algorithm for finding largest eigenpair of small general complex matrix

  - by mklassen

  I am looking for an efficient algorithm to find the largest eigenpair of a small, general (non-square, non-sparse, non-symmetric), complex matrix, A, of size m x n. By small I mean m and n is typically between 4 and 64 and usually around 16, but with m not equal to n. This problem is straight forward to solve with the general LAPACK SVD algorithms, i.e. gesvd or gesdd. However, as I am solving millions of these problems and only require the largest eigenpair, I am looking for a more efficient algorithm. Additionally, in my application the eigenvectors will generally be similar for all cases. This lead me to investigate Arnoldi iteration based methods, but I have neither found a good library nor algorithm that applies to my small general complex matrix. Is there an appropriate algorithm and/or library?

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• Fuzzy Regular Expressions

  - by Thomas Ahle

  In my work I have with great results used approximate string matching algorithms such as Damerau–Levenshtein distance to make my code less vulnerable to spelling mistakes. Now I have a need to match strings against simple regular expressions such TV Schedule for \d\d (Jan|Feb|Mar|...). This means that the string TV Schedule for 10 Jan should return 0 while T Schedule for 10. Jan should return 2. This could be done by generating all strings in the regex (in this case 100x12) and find the best match, but that doesn't seam practical. Do you have any ideas how to do this effectively?

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• What are some interesting fringe programming topics that might have hands-on training?

  - by hal10001

  Whenever training topic questions are asked, the answers are fairly typical, and involve a pretty limited subset of topics like OO, design patterns, algorithms, web services, SQL, etc., but I wonder if there are some fringe topics that are still applicable to the programming field and would give me a more rounded approach to development. When I think of "fringe", I think of 2600: The Hacker Quarterly articles that discuss how to use real world (sometimes obscure) exploits, or something like Maker Faire that demonstrates embedded systems programming using Arduino. I have around $1500-2000 to spend, and my job entails Java technologies, but that does not limit my options.

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• Red-Black trees - Erasing a node with two non-leaf children

  - by SalamiArmi

  Hi all, I've been implementing my own version of a red-black tree, mostly basing my algorithms from Wikipedia (http://en.wikipedia.org/wiki/Red-black_tree). Its fairly concise for the most part, but there's one part that I would like clarification on. When erasing a node from the tree that has 2 non-leaf (non-NULL) children, it says to move either side's children into the deletable node, and remove that child. I'm a little confused as to which side to remove from, based on that. Do I pick the side randomly, do I alternate betweek sides, or do I stick to the same side for every future deletion?

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• How to structure a Genetic Algorithm class hierarchy?

  - by MahlerFive

  I'm doing some work with Genetic Algorithms and want to write my own GA classes. Since a GA can have different ways of doing selection, mutation, cross-over, generating an initial population, calculating fitness, and terminating the algorithm, I need a way to plug in different combinations of these. My initial approach was to have an abstract class that had all of these methods defined as pure virtual, and any concrete class would have to implement them. If I want to try out two GAs that are the same but with different cross-over methods for example, I would have to make an abstract class that inherits from GeneticAlgorithm and implements all the methods except the cross-over method, then two concrete classes that inherit from this class and only implement the cross-over method. The downside to this is that every time I want to swap out a method or two to try out something new I have to make one or more new classes. Is there another approach that might apply better to this problem?

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• Novel fitness measure for evolutionary image matching simulation

  - by Nick Johnson

  I'm sure many people have already seen demos of using genetic algorithms to generate an image that matches a sample image. You start off with noise, and gradually it comes to resemble the target image more and more closely, until you have a more-or-less exact duplicate. All of the examples I've seen, however, use a fairly straightforward pixel-by-pixel comparison, resulting in a fairly predictable 'fade in' of the final image. What I'm looking for is something more novel: A fitness measure that comes closer to what we see as 'similar' than the naive approach. I don't have a specific result in mind - I'm just looking for something more 'interesting' than the default. Suggestions?

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• What to learn in my summer holidays?

  - by rgksugan

  I am finishing my graduate and i am into a sotware company. I am a fresher and have some knowledge in Java and JEE. I can program servlets and JSP and have also developed some Swing applications. I dont have that much knowledge in web frameworks. I want to use my holidays usefully at the same time i dont want to spend a lot of time into programming. What can i learn. Suggest me something usefull. I prefer learning some programming tips/algorithms.

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• How to extend WPF hit testing zone for a Path object.

  - by user275587

  Wpf hit testing is pretty good but the only method I found to extend the hit zone is to put a transparent padding area around your object. I can't find any method to add a transparent area arround a Path object. The path is very thin and I would like to enable hit testing if the user clicks near the path. I can't find any method to extend the path object with a transparent area like the image below : I tried to used a partially transparent stroke brush but I ran into the problem described here : http://stackoverflow.com/questions/1412833/how-can-i-draw-a-soft-line-in-wpf-presumably-using-a-lineargradientbrush I also tried to put an adorner over my line but because of WPF anti-aliasing algorithms, the position is way off when I zoom in my canvas and interfere with other objects hit-testing in a bad way. Any suggestion to extend the hit testing zone would be highly appreciated. Thanks, Kumar

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• Concurrency Problem in Java ...

  - by Tara Singh

  I am designing a client-server chat application in Java. This is a secure application where the messages are exchanged using cryptographic algorithms. I have one server and it can support many clients. My problem is that when one client logs on the server it works fine, but when another user logs into the system, the server starts giving me bad padding exceptions for the encrypted text. I am not able to figure out the problem, according to my logic, when new connection request to server is made, the server creates a thread for listening to the client. Is it possible that once the instance of thread class is created, it does all the processing correctly for the first client, but not for the second client because the variables in server listener thread class already have some previous value, and thus the encrypted text is not decrypted properly? Please advise how I can make this process more robust so that the number of clients does not affect how well the server functions.

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• Computing orientation of a square and displaying an object with the same orientation

  - by Robin

  Hi, I wrote an application which detects a square within an image. To give you a good understanding of how such an image containing such a square, in this case a marker, could look like: What I get, after the detection, are the coordinates of the four corners of my marker. Now I don't know how to display an object on my marker. The object should have the same rotation/angle/direction as the marker. Are there any papers on how to achieve that, any algorithms that I can use that proofed to be pretty solid/working? It doesn't need to be a working solution, it could be a simple description on how to achieve that or something similar. If you point me at a library or something, it should work under linux, windows is not needed but would be great in case I need to port the application at some point. I already looked at the ARToolkit but they you camera parameter files and more complex matrices while I only got the four corner points and a single image instead of a whole video / camera stream.

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• How to spot empty parking spaces?

  - by mithila

  I want to do a final year B.Sc project on parking space detection. Can anybody give me some link related to it? Any text-book, tutorial or anything? What would be prerequisite for this project? What type of skills(programming/math) are needed? What are the initial steps to do? What type of readings(algorithms of image processing) are needed? Detail added in comments: i'm going to use camera, not infrared. i would like to use still images, or one camera which captures images from a parking lot. i think reak-time processing will be tough, at this moment i just need to start the project. so still images will work fine. but later it may b a real-time project

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