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  • What is the best way to detect white color?

    - by dnul
    I'm trying to detect white objects in a video. The first step is to filter the image so that it leaves only white-color pixels. My first approach was using HSV color space and then checking for high level of VAL channel. Here is the code: //convert image to hsv cvCvtColor( src, hsv, CV_BGR2HSV ); cvCvtPixToPlane( hsv, h_plane, s_plane, v_plane, 0 ); for(int x=0;x<srcSize.width;x++){ for(int y=0;y<srcSize.height;y++){ uchar * hue=&((uchar*) (h_plane->imageData+h_plane->widthStep*y))[x]; uchar * sat=&((uchar*) (s_plane->imageData+s_plane->widthStep*y))[x]; uchar * val=&((uchar*) (v_plane->imageData+v_plane->widthStep*y))[x]; if((*val>170)) *hue=255; else *hue=0; } } leaving the result in the hue channel. Unfortunately, this approach is very sensitive to lighting. I'm sure there is a better way. Any suggestions?

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  • How do I best do balanced quoting with Perl's Regexp::Grammars?

    - by Evan Carroll
    Using Damian Conway's Regexp::Grammars, I'm trying to match different balanced quoting ('foo', "foo", but not 'foo") mechanisms -- such as parens, quotes, double quotes, and double dollars. This is the code I'm currently using. <token: pair> \'<literal>\'|\"<literal>\"|\$\$<literal>\$\$ <token: literal> [\S]+ This generally works fine and allows me to say something like: <rule: quote> QUOTE <.as>? <pair> My question is how do I reform the output, to exclude the needles notation for the pair token? { '' => 'QUOTE AS \',\'', 'quote' => { '' => 'QUOTE AS \',\'', 'pair' => { 'literal' => ',', '' => '\',\'' } } }, Here, there is obviously no desire to have pair in between, quote, and the literal value of it. Is there a better way to match 'foo', "foo", and $$foo$$, and maybe sometimes ( foo ) without each time creating a needless pair token? Can I preprocess-out that token or fold it into the above? Or, write a better construct entirely that eliminates the need for it?

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  • OPTICS Clustering algorithm. How to get the best epsilon

    - by Marco Galassi
    I am implementing a project which needs to cluster geographical points. OPTICS algorithm seems to be a very nice solution. It needs just 2 parameters as input(MinPts and Epsilon), which are, respectively, the minimum number of points needed to consider them as a cluster, and the distance value used to compare if two points are in can be placed in same cluster. My problem is that, due to the extreme variety of the points, I can't set a fixed epsilon. Just look at the image below. The same points structure but in a different scale would result very different. Suppose to set MinPts=2 and epsilon = 1Km. On the left, the algorithm would create 2 clusters(red and blue), but on the right it would create one single cluster containing all of the points(red), but I would like to obtain 2 clusters even on the right. So my question is: is there any kind of way to calculate dynamically the epsilon value to get this result? Thank you very much and excuse my for my poor english. Marco

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  • Public class: The best way to store and access NSMutableDictionary?

    - by meridimus
    I have a class to help me store persistent data across sessions. The problem is I want to store a running sample of the property list or "plist" file in an NSMutableArray throughout the instance of the Persistance class so I can read and edit the values and write them back when I need to. The problem is, as the methods are publicly defined I cannot seem to access the declared NSMutableDictionary without errors. The particular error I get on compilation is: warning: 'Persistence' may not respond to '+saveData' So it kind of renders my entire process unusable until I work out this problem. Here is my full persistence class (please note, it's unfinished so it's just to show this problem): Persistence.h #import <UIKit/UIKit.h> #define kSaveFilename @"saveData.plist" @interface Persistence : NSObject { NSMutableDictionary *saveData; } @property (nonatomic, retain) NSMutableDictionary *saveData; + (NSString *)dataFilePath; + (NSDictionary *)getSaveWithCampaign:(NSUInteger)campaign andLevel:(NSUInteger)level; + (void)writeSaveWithCampaign:(NSUInteger)campaign andLevel:(NSUInteger)level withData:(NSDictionary *)saveData; + (NSString *)makeCampaign:(NSUInteger)campaign andLevelKey:(NSUInteger)level; @end Persistence.m #import "Persistence.h" @implementation Persistence @synthesize saveData; + (NSString *)dataFilePath { NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString *documentsDirectory = [paths objectAtIndex:0]; return [documentsDirectory stringByAppendingPathComponent:kSaveFilename]; } + (NSDictionary *)getSaveWithCampaign:(NSUInteger)campaign andLevel:(NSUInteger)level { NSString *filePath = [self dataFilePath]; if([[NSFileManager defaultManager] fileExistsAtPath:filePath]) { NSLog(@"File found"); [[self saveData] setDictionary:[[NSDictionary alloc] initWithContentsOfFile:filePath]]; // This is where the warning "warning: 'Persistence' may not respond to '+saveData'" occurs NSString *campaignAndLevelKey = [self makeCampaign:campaign andLevelKey:level]; NSDictionary *campaignAndLevelData = [[self saveData] objectForKey:campaignAndLevelKey]; return campaignAndLevelData; } else { return nil; } } + (void)writeSaveWithCampaign:(NSUInteger)campaign andLevel:(NSUInteger)level withData:(NSDictionary *)saveData { NSString *campaignAndLevelKey = [self makeCampaign:campaign andLevelKey:level]; NSDictionary *saveDataWithKey = [[NSDictionary alloc] initWithObjectsAndKeys:saveData, campaignAndLevelKey, nil]; //[campaignAndLevelKey release]; [saveDataWithKey writeToFile:[self dataFilePath] atomically:YES]; } + (NSString *)makeCampaign:(NSUInteger)campaign andLevelKey:(NSUInteger)level { return [[NSString stringWithFormat:@"%d - ", campaign+1] stringByAppendingString:[NSString stringWithFormat:@"%d", level+1]]; } @end I call this class like any other, by including the header file in my desired location: @import "Persistence.h" Then I call the function itself like so: NSDictionary *tempSaveData = [[NSDictionary alloc] [Persistence getSaveWithCampaign:currentCampaign andLevel:currentLevel]];

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  • What is the best IDE to use with the Symfony framework?

    - by Failpunk
    I'm looking for an IDE with use with the Symfony Framework. I have a bit of experience using the NetBeans 6.5 IDE but it does not always seem to complete the class methods, plus it doesn't seem to have any PHP code snippets built in. Here are the features I would ideally like to have, in order of importance, from an IDE: Code completion of all the Symfony and Propel class methods (I can never remember them) Code templates,(class skeletons, HTML structures, Symfony templates?) Straight-forward code debugging Source Control

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  • What's the best way to offer javascript embed that won't slow a page down?

    - by Shpigford
    I have a chunk of javascript that users can copy and paste to put on their sites. I'm currently using the following code (ala WEDJE) that allows the rest of the page to load even if my script is slow or not responding. <script type="text/javascript"> var number = "987654321"; var key = "123abc"; (function(){ document.write('<div id="ttp"></div>'); s=document.createElement('script'); s.type="text/javascript"; s.src="http://example.com/javascripts/embed.js?" + Math.random(); setTimeout("document.getElementById('ttp').appendChild(s);",1); })() </script> But that method is a few years old and so I wasn't sure if there was a more efficient way of doing the same thing that others have come up with.

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  • How best to associate code with events in jQuery?

    - by Ned Batchelder
    Suppose I have a <select> element on my HTML page, and I want to run some Javascript when the selection is changed. I'm using jQuery. I have two ways to associate the code with the element. Method 1: jQuery .change() <select id='the_select'> <option value='opt1'>One</option> <option value='opt2'>Two</option> </select> <script> $('#the_select').change(function() { alert('Changed!'); }); </script> Method 2: onChange attribute <select id='the_select' onchange='selectChanged();'> <option value='opt1'>One</option> <option value='opt2'>Two</option> </select> <script> function selectChanged() { alert('Changed!'); } </script> I understand the different modularity here: for example, method 1 keeps code references out of the HTML, but method 2 doesn't need to mention HTML ids in the code. What I don't understand is: are there operational differences between these two that would make me prefer one over the other? For example, are there edge-case browsers where one of these works and the other doesn't? Is the integration with jQuery better for either? Does the late-binding of the code to the event make a difference in the behavior of the page? Which do you pick and why?

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  • What is the best logging solution for a C# .NET 3.5 project?

    - by Odd
    My team is about to start a new enterprise wide ASP.NET development project, quite possibly the largest undertaken by my department so far and the largest project that I've ever worked on. I'm looking for a good logging solution for the system. Firstly, what logging tools are currently available and widely used? Secondly, for an ASP.NET (probably MVC) enterprise applicaiton, which tool is most appropriate based on your experience? So far I've used Log4net almost exclusively for all my previous projects. It's a fantastic tool, however I would like to see if there is anything I've not used out there before I start a project of this magnitude or if there is any reason I would not want to use Log4net for a project of this size.

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  • Best way to bundles photos with app: files or in sqlite database?

    - by Bryan Denny
    Lets say that I have an app that lets you browse through a listing of cars found in a Sqlite database. When you click on a car in the listing, it'll open up a view with the description of the car and a photo of the car. My question is: should I keep the photo in the database as a binary data column in the row for this specific car, or should I have the photo somewhere in the resources directory? Which is better to do? Are there any limitations of Sqlite in terms of how big a binary data column can be? The database will be pretty much be read only and bundled with the app (so the user wouldn't be inserting any cars and their photos).

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  • Best place to check user authenticity in a back end module where all pages are only available to mem

    - by understack
    I've a backend module which could only be accessed by only authorized members. So I need to check authenticity for all actions and for all controllers. Currently I'm doing it inside preDispatch() functions inside controller classes. So it takes care of all the actions inside that controller. But still I've to do it for all controllers. Is there a place I could check it for all the controllers as well. So basically I want one place authenticity check for whole backend module. Can I do it in bootstrap?

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  • How best to calculate derived currency rate conversions using C#/LINQ?

    - by chillitom
    class FxRate { string Base { get; set; } string Target { get; set; } double Rate { get; set; } } private IList<FxRate> rates = new List<FxRate> { new FxRate {Base = "EUR", Target = "USD", Rate = 1.3668}, new FxRate {Base = "GBP", Target = "USD", Rate = 1.5039}, new FxRate {Base = "USD", Target = "CHF", Rate = 1.0694}, new FxRate {Base = "CHF", Target = "SEK", Rate = 8.12} // ... }; Given a large yet incomplete list of exchange rates where all currencies appear at least once (either as a target or base currency): What algorithm would I use to be able to derive rates for exchanges that aren't directly listed? I'm looking for a general purpose algorithm of the form: public double Rate(string baseCode, string targetCode, double currency) { return ... } In the example above a derived rate would be GBP-CHF or EUR-SEK (which would require using the conversions for EUR-USD, USD-CHF, CHF-SEK) Whilst I know how to do the conversions by hand I'm looking for a tidy way (perhaps using LINQ) to perform these derived conversions perhaps involving multiple currency hops, what's the nicest way to go about this?

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  • R selecting duplicate rows

    - by Matt
    Okay, I'm fairly new to R and I've tried to search the documentation for what I need to do but here is the problem. I have a data.frame called heeds.data in the following form (some columns omitted for simplicity) eval.num, eval.count, ... fitness, fitness.mean, green.h.0, green.v.0, offset.0, green.h.1, green.v.1,...green.h.7, green.v.7, offset.7... And I have selected a row meeting the following criteria: best.fitness <- min(heeds.data$fitness.mean[heeds.data$eval.count = 10]) best.row <- heeds.data[heeds.data$fitness.mean == best.fitness] Now, what I want are all of the other rows with that have columns green.h.0 to offset.7 (a contiguous section of columns) equal to the best.row Basically I'm looking for rows that have some of the conditions the same as the "best" row. I thought I could just do this, heeds.best <- heeds.data$fitness[ heeds.data$green.h.0 == best.row$green.h.0 & ... ] But with 24 columns it seems like a stupid method. Looking for something a bit simpler with less manual typing. Thanks!

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  • What are the best authentication and authorization examples for your favorite web framework?

    - by Nathan Feger
    I have been looking through java web frameworks lately (though this question need not be limited to java), and I noticed that most examples on web framework websites leave out auth & auth examples in their stock documentation. one ruby example: acts_as_authenticated (link?) grails has: http://www.grails.org/Authentication+Plugin Anyway, please throw up some links to your framework of choice, and a link to a nice walkthrough to implementing an auth&auth solution.

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  • Best way to keep a large number of hobby projects alive; open sourcing?

    - by Daan van Yperen
    Because my time is limited I can usually only focus on one or two of my hobby projects, while the others sit there wasting away. I am looking for a solution that would allow me to divide my time better. is open sourcing where I take the role of guiding the project realistic, or are there better solutions? In my case, one project has a reasonably sized community of users going for it but is currently closed source. There have been requests to open source it.

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  • Best way to draw a bar chart in LaTeX?

    - by Tae
    I was looking for it here in Stack Overflow as in Google, and I found a lot of packages to draw, but it seems a complex task, so I would like to know which is the most appropriate package to draw bars, and associate data to it. Also I was looking for a code example, but I did not have luck.

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  • enterprise libaray confiuration 4.0

    - by prince23
    hi, i am using enterprise libaray confiuration 4.0. and here i have set the file size as rollSizeKB="20" but once my file size reaches 9kb. a new file is created. what is te issue. why is it creating new file once ut reaches 9KB. <add fileName="c:\Exception.log" footer="----------------------------------------" formatter="Text Formatter" header="----------------------------------------" rollFileExistsBehavior="Increment" rollInterval="None" rollSizeKB="20" timeStampPattern="yyyy-MM-dd" listenerDataType="Microsoft.Practices.EnterpriseLibrary.Logging.Configuration.RollingFlatFileTraceListenerData, Microsoft.Practices.EnterpriseLibrary.Logging, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" traceOutputOptions="Timestamp" filter="All" type="Microsoft.Practices.EnterpriseLibrary.Logging.TraceListeners.RollingFlatFileTraceListener, Microsoft.Practices.EnterpriseLibrary.Logging, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" name="Exception Policy" /> any help would be great thank you

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  • Is it really best to make site without using <div>, using semantic tags only?

    - by jitendra
    I found this on net in google search and see article here: http://www.thatcssguy.com/limit-your-divs/ See his final layout here: http://www.nodivs.com/ Some quotes from article 1 When I limited the use of my divs all the major browser including both IE6 and IE7 would render the sites nearly perfectly. Or with very little fixes needed. 2 it’s magic but proves divs nor tables are necessary for layout Should we try to make sites like this?

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  • What's the best way to add scripting to an Android app?

    - by Omega
    I have an XML based file format that I'm using to store and load instances of objects. I'm interested in adding some scripting support to those objects so that they can respond to events. That said, I also don't want to cripple performance. Are there any well known scripting options for Android - maybe even ones where while loading, I can pre-compile and cache the scripts?

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