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  • Count the number of objects in an Image

    - by kunjaan
    I am investigating the possibility of image processing to identify certain objects and also count them in an image. I will be given a picture and I need to identify the number of boxes present in that image. Does anybody have any experience with any Machine Vision/ Image Processing libraries like ImageJ, Fiji, JAI, jMagick ,Java Vision Toolkit? Which do you think is best suited for the job? What do you guys suggest? If the APIs can be used from Java, it would be better. Thank you. Edit: I am dealing with warehouse brown boxes. Yes I am talking about regular photos. The source is usually a mobile phone picture.

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  • How do software events work internally?

    - by Duddle
    Hello! I am a student of Computer Science and have learned many of the basic concepts of what is going on "under the hood" while a computer program is running. But recently I realized that I do not understand how software events work efficiently. In hardware, this is easy: instead of the processor "busy waiting" to see if something happened, the component sends an interrupt request. But how does this work in, for example, a mouse-over event? My guess is as follows: if the mouse sends a signal ("moved"), the operating system calculates its new position p, then checks what program is being drawn on the screen, tells that program position p, then the program itself checks what object is at p, checks if any event handlers are associated with said object and finally fires them. That sounds terribly inefficient to me, since a tiny mouse movement equates to a lot of cpu context switches (which I learned are relatively expensive). And then there are dozens of background applications that may want to do stuff of their own as well. Where is my intuition failing me? I realize that even "slow" 500MHz processors do 500 million operations per second, but still it seems too much work for such a simple event. Thanks in advance!

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  • Will this make the object thread-safe?

    - by sharptooth
    I have a native Visual C++ COM object and I need to make it completely thread-safe to be able to legally mark it as "free-threaded" in th system registry. Specifically I need to make sure that no more than one thread ever accesses any member variable of the object simultaneously. The catch is I'm almost sure that no sane consumer of my COM object will ever try to simultaneously use the object from more than one thread. So I want the solution as simple as possible as long as it meets the requirement above. Here's what I came up with. I add a mutex or critical section as a member variable of the object. Every COM-exposed method will acquire the mutex/section at the beginning and release before returning control. I understand that this solution doesn't provide fine-grained access and this might slow execution down, but since I suppose simultaneous access will not really occur I don't care of this. Will this solution suffice? Is there a simpler solution?

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  • When may I ask a question to fellow developers? (Rules before asking questions).

    - by Zwei Steinen
    I assigned a quite simple task to one junior developer today, and he kept pinging me EVERY 5 minutes for HOURS, asking STEP BY STEP, what to do. Whenever something went wrong, he simply copy&pasted the log and basically wrote, "An exception occurred. What should I do?" So I finally had to tell him, "If you want to be a developer, please start thinking a little bit. Read the error message. That's what they are for!". I also however, tell junior developers to ask questions before spending too much time trying to solve it themselves. This might sound contradictory, but I feel there is some kind of an implicit rule that distinguishes questions that should be asked fairly quickly and that should not (and I try to follow those rules when I ask questions..) So my question is, do you have any rules that you follow, or expect others to follow on asking questions? If so, what are they? Let me start with my own. If you have struggled for more than 90 min, you may ask that question (exceptions exists). If you haven't struggled for more than 15 min, you may not ask that question (if you are sure that the answer can not be found within 15 min, this rule does not have to apply). If it is completely out of your domain and you do not plan to learn that domain, you may ask that question after 15 min (e.g. if I am a java programmer and need to back up the DB, I may ask the DBA what procedure to follow after googling for 15 min). If it is a "local" question, whose answer is difficult to derive or for which resources is difficult to get (e.g. asking an colleague "what method xxx does" etc.), you may ask that question after 15 min. If the answer for it is difficult to derive, and you know that the other person knows the answer, you may ask the question after 15 min (e.g. asking a hibernate expert "What do I need to change else to make this work?". If the process to derive the answer is interesting and is a good learning opportunity, you may ask for hints but you may not ask for answers! What are your rules?

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  • C# logic order and compiler behavior

    - by Terrapin
    In C#, (and feel free to answer for other languages), what order does the runtime evaluate a logic statement? Example: DataTable myDt = new DataTable(); if (myDt != null && myDt.Rows.Count > 0) { //do some stuff with myDt } Which statement does the runtime evaluate first - myDt != null or: myDt.Rows.Count > 0 ? Is there a time when the compiler would ever evaluate the statement backwards? Perhaps when an "OR" operator is involved?

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  • Reconstructing simple 3d enviroment(room) from photo

    - by Riz
    I have photo of a room with three walls and floor/ceiling or both. I am trying to reconstruct this room in 3d asking user for minimal input. Right now I use 8 points defined by user, angles of left and right wall(they can be quite different from 90) and one size "InLeftBottom-InRightBottom"(I need to have real size of this room for later use). I have no info about user's camera(I can read EXIF to get FOV and use constant height but this can be only used as additional info). Is this possible to ask user for less info? Maybe it's possible to get wall angles without user interaction? Or maybe I am completly wrong and should use different approach?

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  • Can you use #defined values in if statements (In C programs)?

    - by Jordan S
    I am new at C programming. I thought when you type something like #define Const 5000 that the compiler just replaces every instance of Const with 5000 at compile time. Is that wrong? I try doing this in my code and I get a syntax error. Why can't i do this? #define STEPS_PER_REV 12345 ... in some function if(CurrentPosition >= STEPS_PER_REV) { // do some stuff here } The compiler complains about the if statement with a syntax error that gives me no details.

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  • Associating an Object with other Objects and Properties of those Objects

    - by alzoid
    I am looking for some help with designing some functionality in my application. I already have something similar designed but this problem is a little different. Background: In my application we have different Modules. Data in each module can be associated to other modules. Each Module is represented by an Object in our application. Module 1 can be associated with Module 2 and Module 3. Currently I use a factory to provide the proper DAO for getting and saving this data. It looks something like this: class Module1Factory { public static Module1BridgeDAO createModule1BridgeDAO(int moduleid) { switch (moduleId) { case Module.Module2Id: return new Module1_Module2DAO(); case Module.Module3Id: return new Module1_Module3DAO(); default: return null; } } } Module1_Module2 and Module1_Module3 implement the same BridgeModule interface. In the database I have a Table for every module (Module1, Module2, Module3). I also have a bridge table for each module (they are many to many) Module1_Module2, Module1_Module3 etc. The DAO basically handles all code needed to manage the association and retrieve its own instance data for the calling module. Now when we add new modules that associate with Module1 we simply implement the ModuleBridge interface and provide the common functionality. New Development We are adding a new module that will have the ability to be associated with other Modules as well as specific properties of that module. The module is basically providing the user the ability to add their custom forms to our other modules. That way they can collect additional information along with what we provide. I want to start associating my Form module with other modules and their properties. Ie if Module1 has a property Category, I want to associate an instance From data with that property. There are many Forms. If a users creates an instance of Module2, they may always want to also have certain form(s) attached to that Module2 instance. If they create an instance of Module2 and select Category 1, then I may want additional Form(s) created. I prototyped something like this: Form FormLayout (contains the labels and gui controls) FormModule (associates a form with all instances of a module) Form Instance (create an instance of a form to be filled out) As I thought about it I was thinking about making a new FormModule table/class/dao for each Module and Property that I add. So I might have: FormModule1 FormModule1Property1 FormModule1Property2 FormModule1Property3 FormModule1Property4 FormModule2 FormModule3 FormModule3Property1 Then as I did previously, I would use a factory to get the proper DAO for dealing with all of these. I would hand it an array of ids representing different modules and properties and it would return all of the DAOs that I need to call getForms(). Which in turn would return all of the forms for that particular bridge. Some points This will be for a new module so I dont need to expand on the factory code I provided. I just wanted to show an example of what I have done in the past. The new module can be associated with: Other Modules (ie globally for any instance of that module data), Other module properties (ie only if the Module instance has a certian value in one of its properties) I want to make it easy for developers to add associations with other modules and properties easily Can any one suggest any design patterns or strategy's for achieving this? If anything is unclear please let me know. Thank you, Al

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  • Extensions methods and forward compatibilty of source code.

    - by TcKs
    Hi, I would like solve the problem (now hypothetical but propably real in future) of using extension methods and maginification of class interface in future development. Example: /* the code written in 17. March 2010 */ public class MySpecialList : IList<MySpecialClass> { // ... implementation } // ... somewhere elsewhere ... MySpecialList list = GetMySpecialList(); // returns list of special classes var reversedList = list.Reverse().ToList(); // .Reverse() is extension method /* now the "list" is unchanged and "reveresedList" has same items in reversed order */ /* --- in future the interface of MySpecialList will be changed because of reason XYZ*/ /* the code written in some future */ public class MySpecialList : IList<MySpecialClass> { // ... implementation public MySpecialList Reverse() { // reverse order of items in this collection return this; } } // ... somewhere elsewhere ... MySpecialList list = GetMySpecialList(); // returns list of special classes var reversedList = list.Reverse().ToList(); // .Reverse() was extension method but now is instance method and do something else ! /* now the "list" is reversed order of items and "reveresedList" has same items lake in "list" */ My question is: Is there some way how to prevent this case (I didn't find them)? If is now way how to prevent it, is there some way how to find possible issues like this? If is now way how to find possible issues, should I forbid usage of extension methods? Thanks.

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  • [Embedded Python] Invoking a method on an object

    - by jmucchiello
    Given a PyObject* pointing to a python object, how do I invoke one of the object methods? The documentation never gives an example of this: PyObject* obj = .... PyObject* args = Py_BuildValue("(s)", "An arg"); PyObject* method = PyWHATGOESHERE(obj, "foo"); PyObject* ret = PyWHATGOESHERE(obj, method, args); if (!ret) { // check error... } This would be the equivalent of >>> ret = obj.foo("An arg")

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  • O(N log N) Complexity - Similar to linear?

    - by gav
    Hey All, So I think I'm going to get buried for asking such a trivial but I'm a little confused about something. I have implemented quicksort in Java and C and I was doing some basic comparissons. The graph came out as two straight lines, with the C being 4ms faster than the Java counterpart over 100,000 random integers. The code for my tests can be found here; android-benchmarks I wasn't sure what an (n log n) line would look like but I didn't think it would be straight. I just wanted to check that this is the expected result and that I shouldn't try to find an error in my code. I stuck the formula into excel and for base 10 it seems to be a straight line with a kink at the start. Is this because the difference between log(n) and log(n+1) increases linearly? Thanks, Gav

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  • Tools for viewing logs of unlimited size

    - by jkff
    It's no secret that application logs can go well beyond the limits of naive log viewers, and the desired viewer functionality (say, filtering the log based on a condition, or highlighting particular message types, or splitting it into sublogs based on a field value, or merging several logs based on a time axis, or bookmarking etc.) is beyond the abilities of large-file text viewers. I wonder: Whether decent specialized applications exist (I haven't found any) What functionality might one expect from such an application? (I'm asking because my student is writing such an application, and the functionality above has already been implemented to a certain extent of usability)

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  • client-server application design

    - by nelly
    Hi, i want to create a client-server application using sockets on .net platform and being new to networking programming and i have a dilemma. The client will send data to server often and also the server will notify clients often. What is the best way to design it? should the server keep a thread to communicate with each client until it quits or just the clients send data to the server and it update the clients regularly(few seconds) or none of those? Some help would be great. Thanks guys.

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  • Instantiating Java object with a passed in method

    - by superluminary
    It's been a few years since I've been heavily into Java. Coming back to it I'm seeing this pattern all over the place: ratingBar.setOnRatingBarChangeListener(new OnRatingBarChangeListener() { public void onRatingChanged(RatingBar ratingBar, float rating, boolean fromUser) { // do work } }); This looks more like Functional programming to me. It's a nice pattern but how is it possible to pass a method like this? In the old days a class was a class, and once compiled there was little you could do to it. My questions are: Can anyone let me know what this pattern is called? How can I write a class that can be instantiated in this way. Are there any other useful examples of functional patterns that have made their way into Java? What do I need to Google to read more about this? Thanks.

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  • Given a document select a relevant snippet.

    - by BCS
    When I ask a question here, the tool tips for the question returned by the auto search given the first little bit of the question, but a decent percentage of them don't give any text that is any more useful for understanding the question than the title. Does anyone have an idea about how to make a filter to trim out useless bits of a question? My first idea is to trim any leading sentences that contain only words in some list (for instance, stop words, plus words from the title, plus words from the SO corpus that have very weak correlation with tags, that is that are equally likely to occur in any question regardless of it's tags)

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  • Aliasing `T*` with `char*` is allowed. Is it also allowed the other way around?

    - by StackedCrooked
    Note: This question has been renamed and reduced to make it more focused and readable. Most of the comments refer to the old text. According to the standard objects of different type may not share the same memory location. So this would not be legal: int i = 0; short * s = reinterpret_cast<short*>(&i); // BAD! The standard however allows an exception to this rule: any object may be accessed through a pointer to char or unsigned char: int i = 0; char * c = reinterpret_cast<char*>(&i); // OK However, it is not clear to me if this is also allowed the other way around. For example: char * c = read_socket(...); unsigned * u = reinterpret_cast<unsigned*>(c); // huh? Summary of the answers The answer is NO for two reasons: You an only access an existing object as char*. There is no object in my sample code, only a byte buffer. The pointer address may not have the right alignment for the target object. In that case dereferencing it would result in undefined behavior. On the Intel and AMD platforms it will result performance overhead. On ARM it will trigger a CPU trap and your program will be terminated! This is a simplified explanation. For more detailed information see answers by @Luc Danton, @Cheers and hth. - Alf and @David Rodríguez.

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  • What do you call the concept of dynamic data definition?

    - by DJTripleThreat
    Maybe this is simpler and more straightforward then what I'm thinking but I can't seem to find this concept on google anywhere. The concept is this: You have a table in a database and the table has a specified number of columns. However, it has been asked of me by previous clients that there also be a set of dynamic user defined columns that can be added on the fly. What is this concept called and is it considered a design pattern?

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  • Optimality of Binary Search

    - by templatetypedef
    Hello all- This may be a silly question, but does anyone know of a proof that binary search is asymptotically optimal? That is, if we are given a sorted list of elements where the only permitted operation on those objects is a comparison, how do you prove that the search can't be done in o(lg n)? (That's little-o of lg n, by the way.) Note that I'm restricting this to elements where the only operation permitted operation is a comparison, since there are well-known algorithms that can beat O(lg n) on expectation if you're allowed to do more complex operations on the data (see, for example, interpolation search). Thanks so much! This has really been bugging me since it seems like it should be simple but has managed to resist all my best efforts. :-)

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