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• Python Imaging: YCbCr problems

  - by daver

  Hi, I'm doing some image processing in Python using PIL, I need to extract the luminance layer from a series of images, and do some processing on that using numpy, then put the edited luminance layer back into the image and save it. The problem is, I can't seem to get any meaningful representation of my Image in a YCbCr format, or at least I don't understand what PIL is giving me in YCbCr. PIL documentation claims YCbCr format gives three channels, but when I grab the data out of the image using np.asarray, I get 4 channels. Ok, so I figure one must be alpha. Here is some code I'm using to test this process: import Image as im import numpy as np pengIm = im.open("Data\\Test\\Penguins.bmp") yIm = pengIm.convert("YCbCr") testIm = np.asarray(yIm) grey = testIm[:,:,0] grey = grey.astype('uint8') greyIm = im.fromarray(grey, "L") greyIm.save("Data\\Test\\grey.bmp") I'm expecting a greyscale version of my image, but what I get is this jumbled up mess: http://i.imgur.com/zlhIh.png Can anybody explain to me where I'm going wrong? The same code in matlab works exactly as I expect.

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• has_many :through when join table doesn't contain FK to both tables

  - by seth.vargo

  I have a structure that isn't really a has_many :through example, but I'd like it to behave like one: # user.rb belongs_to :blog has_many :posts # post.rb belongs_to :user # blog.rb has_many :users has_many :posts, :through => :users # this obviously doesn't work becase # both FKs aren't in the blogs table I want to get ALL posts for a blog in an array. I'm aware that I can do this with Ruby using each or getting fancy with collect, but I'd like to let SQL do the work. Can someone explain how I can set up my models in a way that lets me call @blog.posts using SQL, not Ruby? Edit: I know in SQL I can write something like: SELECT * FROM posts WHERE posts.user_id IN ( SELECT users.id FROM users WHERE users.blog_id = 7 ) which obviously shows two queries are needed. I don't think this is possible with a join, but I'm not totally sure. It's obvious that a subquery is needed, but how do I get rails to build that subquery with ARel instead of having to return and use Ruby to loop and collect and such?

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• 2-Version software: Best VCS approach?

  - by Tom R

  I suppose I'd better explain my situation: I'm in the process of developing some software, and I'm at the stage where I'd like to split my project into two branches which differ in features. It so happens that this application is an Android application which I will be deploying on the Market, which has the constraint that every app must have a unique package identifier (sensible, no?). My current approach has been to clone the git repo of my original project, but this causes issues with package names. I want the system to be robust enough so that a bugfix/new feature on one branch will merge into another branch, but only when I want it to. Does anyone have any suggestions?

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• Issue with UITextView in an animation block

  - by collin

  I'm having an issue with a UITextView inside another UIView whose frame is manipulated in an animation block when the keyboard displays. During the animation block the UIView scales beautifully and as expected, but the UITextView jumps out of it's superview(the UIView being animated) at the start of the animation. By the end of the animation, the UITextView ends up in the right place... what gives? Can anybody explain why the UITextView is jumping out of it's container view at the start of the animation? Thanks in advance.

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• Google Street View API v3 : how can I avoid having "fish-eye" effect on Firefox?

  - by Benj

  I'm using google maps API V3 and I'm having trouble displaying correctly the street view within Firefox. I always get the "fish-eye" view (does not happen with Google chrome). So I assumed that the problem came from Firefox. I took a look to the street view options but found nothing. I would like to know if there is an option to have a flatten street view or if it is because Firefox does not support this kind of feature. If someone could explain it to me, I would be grateful. Below, what it looks in Firefox : And what it looks in Chrome :

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• How to use CCR, DSS, VPL (aka Microsoft Robotics Development Studio) outside robotics?

  - by basilmir

  How to use CCR, DSS, VPL (aka Microsoft Robotics Development Studio) outside robotics? I am looking for guidance in this field. I have tried all the examples and find the framework intriguing. Can anyone post other uses and examples, outside robotics? PS. I am looking for someone to explain some of the more complex stuff to me. I have questions regarding different implementations. If anyone is interested, i am willing to pay for a one to one talk (consulting) on the advanced topics. You can reach me via email, same name as here.

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• killall httpd for sleep process

  - by user172697

  Hello guys this shell explain the issue , after executing the .sh file halt and nothing happen , any clue where is my mistake its kill httpd if there is more than 10 sleep process and start the httpd with zero sleep process #!/bin/bash #this means loop forever while [ 1 ]; do HTTP=`ps auwxf | grep httpd | grep -v grep | wc -l`; #the above line counts the number of httpd processes found running #and the following line says if there were less then 10 found running if [ $[HTTP] -lt 10 ]; then killall -9 httpd; #inside the if now, so there are less then 10, kill them all and wait 1 second sleep 1; #start apache /etc/init.d/httpd start; fi; #all done, sleep for ten seconds before we loop again sleep 10;done

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• How to order the images in a mysql database?

  - by user305270

  Hy! Here is my problem: i have a profile and this profile has for example 100 images. When someone visit this profile the first image will be the first result of my query that sorts by updated_at. But if the user would want to put the image with the (id = 8) to be the first, then (id = 22) then (id = 88) and so on? I need to put another field or is really necessary a new table to make a custom sort on images? and maybe someone explain this to me how to do? thanks, i appreciate your help ;)

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• jQuery .val Enigma between two input boxes

  - by Matt

  I'm trying to get it so that if I move a red div-square around the screen using jQuery UI and jQuery, then an input field updates with the position of the div. I got that working with a simple .val. But, it's hard to explain why, but I need to make it so that when I move the square, it updates my input box, and when the input box value is changed, another input box reflects the new value of the old input box. Do I make any sense, coz I'm confusing myself :). I made a jsfiddle, so perhaps it'll make more sense there. If you move the red square, then the input box directly above it updates, but the input box above that does not, even though it is programmed to reflect the value of the input box below itself. P.S. Is this specific to only jQuery, or is this problem present in all of JavaScript. Thanks! http://jsfiddle.net/xmCsq/27/

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• Send a "304 Not Modified" for images stored in the datastore

  - by Emilien

  I store user-uploaded images in the Google App Engine datastore as db.Blob, as proposed in the docs. I then serve those images on /images/<id>.jpg. The server always sends a 200 OK response, which means that the browser has to download the same image multiple time (== slower) and that the server has to send the same image multiple times (== more expensive). As most of those images will likely never change, I'd like to be able to send a 304 Not Modified response. I am thinking about calculating some kind of hash of the picture when the user uploads it, and then use this to know if the user already has this image (maybe send the hash as an Etag?) I have found this answer and this answer that explain the logic pretty well, but I have 2 questions: Is it possible to send an Etag in Google App Engine? Has anyone implemented such logic, and/or is there any code snippet available?

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• Finding recurrence relations of an algorithm

  - by Roarke

  I'm reading my algorithms text book, and I'm reading about recurrence relations and finding the algorithms big O complexity. I run across this line "In the case of the merge-sort algorithm, we get the recurrence equation: t(n) = b if n < 2 = 2t(n/2) +bn if n >= 2 for b > 0 my response was "how the heck did we know that?!?!" So i'm wondering if there is a systematic approach, or just a logical way of getting these recurrence relations from the algorithms can some one explain where the b and the two 2's come from?

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• Creating combinations that have no more one intersecting element

  - by khuss

  I am looking to create a special type of combination in which no two sets have more than one intersecting element. Let me explain with an example: Let us say we have 9 letter set that contains A, B, C, D, E, F, G, H, and I If you create the standard non-repeating combinations of three letters you will have 9C3 sets. These will contain sets like ABC, ABD, BCD, etc. I am looking to create sets that have at the most only 1 common letter. So in this example, we will get following sets: ABC, ADG, AEI, AFH, BEH, BFG, BDI, CFI, CDH, CEG, DEF, and GHI - note that if you take any two sets there are no more than 1 repeating letter. What would be a good way to generate such sets? It should be scalable solution so that I can do it for a set of 1000 letters, with sub set size of 4. Any help is highly appreciated. Thanks

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• What do you do when you feel you need a variatic list comprehension?

  - by cspyr0

  I would like to make a method where I could give it a list of lengths and it would return all combinations of cartesian coordinates up to those lengths. Easier to explain with an example: cart [2,5] Prelude> [ [0,0],[0,1],[0,2],[0,3],[0,4],[1,0],[1,1],[1,2],[1,3],[1,4] ] cart [2,2,2] Prelude> [ [0,0,0],[0,0,1],[0,1,0],[0,1,1],[1,0,0],[1,0,1],[1,1,0],[1,1,1] ] A simple list comprehension won't work because I don't know how long the lists are going to be. While I love Haskell's simplicity for many problems, this is one that I could write procedurally (in C or something) in 5 minutes whereas Haskell gives me an aneurysm! A solution to this specific problem would help me out a lot; I'd also love to hear about your thought processes when tackling stuff like this.

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• Static and overriding in Java

  - by Abhishek Jain

  public class B { static int i =1; public static int multiply(int a,int b) { return i; } public int multiply1(int a,int b) { return i; } public static void main(String args[]) { B b = new A(); System.out.println(b.multiply(5,2)); System.out.println(b.multiply1(5,2)); } } class A extends B { static int i =8; public static int multiply(int a,int b) { return 5*i; } public int multiply1(int a,int b) { return 5*i; } } Output: 1 40 Why is it so? Please explain.

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• Does mod_rewrite in subdirectories' .htaccess override higher levels?

  - by Ryan

  I'm using mod_rewrite to map my old directory structure to a new one. I have the following rule in my top-level .htaccess file, and it works: RewriteEngine On RewriteCond %{REQUEST_URI} /blog/archives/(.*) RewriteRule ^.*$ /archives/%1 [L,R=301] As you can guess, this takes http://example.com/blog/archives/00001.php and redirects it to http://example.com/archives/00001.php. But when I add these rewrite rules to the .htaccess file in the /blog directory RewriteEngine on RewriteRule atom.xml$ /atom.xml [L,R=301] the top-level redirect no longer works. If I move the rule in the /blog .htaccess file to the top-levle file both rules work. Can someone explain what is happening here?

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• tomcat 6 - Cluster / BackupManager

  - by Kevin

  Hi, I have a question regarding Clustering (session replication/failover) in tomcat 6 using BackupManager. Reason I chose BackupManager, is because it replicates the session to only one other server. I am going to run through the example below to try and explain my question. I have 6 nodes setup in a tomcat 6 cluster with BackupManager. The front end is one Apache server using mod_jk with sticky session enabled Each node has 1 session each. node1 has a session from client1 node2 has a session from client2 .. .. Now lets say node1 goes down ; assuming node2 is the backup, node2 now has two sessions (for client2 and client1) The next time client1 makes a request, what exactly happens ? Does Apache "know" that node1 is down and does it send the request directly to node2 ? =OR= does it try each of the 6 instances and find out the hard way who the backup is ?

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• GLOBAL problem with javascript

  - by Syom

  There is some problem, i can't understand anyway. look at this code please <script type="text/javascript"> function math(x) { var y; y = x*10; alert(y); } </script> <input type="button" onclick="math(0.011)"> What must be alerted after i click on button? i think 0.11, but no, it alerts 0.10999999999999999 explain please this behavior. thanks in advance

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• [C#] Async threaded tcp server

  - by mark_dj

  I want to create a high performance server in C# which could take about ~10k clients. Now i started writing a TcpServer with C# and for each client-connection i open a new thread. I also use one thread to accept the connections. So far so good, works fine. The server has to deserialize AMF incoming objects do some logic ( like saving the position of a player ) and send some object back ( serializing objects ). I am not worried about the serializing/deserializing part atm. My main concern is that I will have a lot of threads with 10k clients and i've read somewhere that an OS can only hold like a few hunderd threads. Are there any sources/articles available on writing a decent async threaded server ? Are there other possibilties or will 10k threads work fine ? I've looked on google, but i couldn't find much info about design patterns or ways which explain it clearly

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• How to execute in javascriptfunction in asp.net c#

  - by shree-khanal

  i have a textarea which i want to disable when I check a checkbox. I made a working demo in plain html and javascript, but When I am migrating to Asp.net, neither the function is being executed nor I can keep the onselect event in my check box. <asp:CheckBox ID="ChkOthers" runat="server" Text="Others(Please Explain)" Width="205px" AutoPostBack="True" OnCheckedChanged="ChkOthers_CheckedChanged" /></td> <asp:TextBox ID="TxtOtherReason" runat="server" MaxLength="1024" TextMode="MultiLine" ></asp:TextBox></td> i want to create client side validation when check box is checked textbox is enable else disable.

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• Socket ping-pong performance

  - by Kamil_H

  I have written two simple programs (tried it in C++ and C#). This is pseudo code: -------- Client --------------- for(int i = 0; i < 200.000; i++) { socket_send("ping") socket_receive(buff) } --------- Server ------------- while(1) { socket_receive(buff) socket_send("pong") } I tried it on Windows. Execution time of client is about 45 seconds. Can somebody explain me why this takes so long? I understand that if there were real network connection between client and server the time of one 'ping-pong' would be: generate_ping + send_via_network + generate_pong + send_via_network but here everything is done in 'local' mode. Is there any way to make this inter process ping-pong faster using network sockets (I'm not asking about shared memory for example :) )

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• What is "sentry object" in C++?

  - by Romain Hippeau

  I answered this question, and Potatoswatter answered too as The modern C++ equivalent would be a sentry object: construct it at the beginning of a function, with its constructor implementing call(), and upon return (or abnormal exit), its destructor implements I am not familiar with using sentry objects in C++. I thought they were limited to input and output streams. Could somebody explain to me about C++ sentry objects as well as how to use them as an around interceptor for one or more methods in a class ? i.e. How to do this ? Sentry objects are very similar indeed. On the one hand they require explicit instantiation (and being passed this) but on the other hand you can add to them so that they check not only the invariants of the class but some pre/post conditions for the function at hand.

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• How to change the text color in a disabled edit box using MFC?

  - by anand.arumug

  Hello all, I have a dialog in which the edit box is disabled but the text should be displayed in red instead of the default grey. I tried the following: void CMyEdit::OnEnable(BOOL bEnable) { CEdit::OnEnable(bEnable); if (bEnable) { m_BackGroundColor = kRGBWhite; } else { m_BackGroundColor = kRGBDefaultGray; } m_TextColor = kRGBRed; m_BackgroundBrush.DeleteObject(); m_BackgroundBrush.CreateSolidBrush(m_BackGroundColor); Invalidate(); } But its still displaying the text in grey only. But if I remove the base class call CEdit::OnEnable(bEnable); then new text color takes effect. Can anyone explain whats wrong in the code? Thanks for your time. cheers...

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• Resizing page format on iReport

  - by pringlesinn

  I've been trying to print a pdf made from iReport in less than a page A4. it's like half A4 page height. I'm using a Line Matrix printer, doesn't matter which one. So, when I try to print 2 files at same file, it should print everything on the right place, but just first file is printed correctly. The second one is based on a A4 page format, and just starts printing after A4 page height is over, skipping a big blank. Where can I set the size of page in iReport? The only thing I could do was setting size of what is shown on screen while I edit the file. I tried my best to explain the situation, any doubts, ask me and I'll try even harder.

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• Type patterns and generic classes in Haskell

  - by finnsson

  I'm trying to understand type patterns and generic classes in Haskell but can't seem to get it. Could someone explain it in laymen's terms? In [1] I've read that "To apply functions generically to all data types, we view data types in a uniform manner: except for basic predefined types such as Float, IO, and ?, every Haskell data type can be viewed as a labeled sum of possibly labeled products." and then Unit, :*: and :+: are mentioned. Are all data types in Haskell automatically versions of the above mentioned and if so how do I figure out how a specific data type is represented in terms of :*:, etc? The users guide for generic classes (ch. 7.16) at haskell.org doesn't mention the predefined types but shouldn't they be handled in every function if the type patterns should be exhaustive? [1] Comparing Approaches to Generic Programming in Haskell, Ralf Hinze, Johan Jeuring, and Andres Löh

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• Auto-Implemented Properties c#

  - by user311130

  Hi all, could someone explain me what's the idea behind using Auto-Implemented Properties c#? public class Customer { public int ID { get; set; } public string Name { get; set; } } I get the motivation to use properties for private field, so we can determine how one can access a private field. But here - it's just like defining the field to be public from the first place. no? Is there a difference between defining a field to be "public const" or define it to have a get-only property ? Thanks Elad

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