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• Is long long in C++ known to be very nasty in terms of precision?

  - by Kevin

  The Given Problem: Given a theater with n rows, m seats, and a list of seats that are reserved. Given these values, determine how many ways two friends can sit together in the same row. So, if the theater was a size of 2x3 and the very first seat in the first row was reserved, there would be 3 different seatings that these two guys can take. The Problem That I'm Dealing With The function itself is supposed to return the number of seatings that there are based on these constraints. The return value is a long long. I've gone through my code many many times...and I'm pretty sure that it's right. All I'm doing is incrementing this one value. However, ALL of the values that my function return differ from the actual solution by 1 or 2. Any ideas? And if you think that it's just something wrong with my code, please tell me. I don't mind being called an idiot just as long as I learn something.

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• ASP.NET problem - Firebug shows odd behaviour

  - by Brandi

  I have an ASP.NET application that does a large database read. It loads up a gridview inside an update panel. In VS2008, just running on my local machine, it runs fantastically. In production (identical code, just published and put on one of our network servers), it runs slow as dirt. Debug is set to false, so this is not the cause of the slow down. I'm not an experienced web developer, so besides that, feel free to suggest the obvious. I have been using Firebug to determine what's going on, and here is what that has turned up: On production, there are around 500 requests. The timeline bar is very short. The size column varies from run to run, but is always the same for the duration of the run. Locally, there are about 30 requests. The timeline bar takes up the entire space. Can anyone shed some light on why this is happening and what I can do to fix it? Also, I can't find much of anything on the web about this, so any references are helpful too.

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• Setup for games animation: How do I know JFrame is finished setting itself up?

  - by Jokkel

  I'm using javax.swing.JFrame to draw game animations using double buffer strategy. First, I set up the frame. JFrame frame = new JFrame(); frame.setVisible(true); Now, I draw an object (let it be a circle, doesn't matter) like this. frame.createBufferStrategy(2); bufferStrategy = frame.getBufferStrategy(); Graphics g = bufferStrategy.getDrawGraphics(); circle.draw(g); bufferStrategy.show(); The problem is that the frame is not always fully set-up when the drawing takes place. Seems like JFrame needs up to three steps in resizing itself, until it reaches it's final size. That makes the drawing slide out of frame or hinders it to appear completely from time to time. I already managed to delay things using SwingUtilities.invokeLater(). While this improved the result, there are still times when the drawing slides away / looks prematurely draw. Any idea / strategy? Thanks in advance. EDIT: Ok thanks so far. I didn't mention that I write a little Pong game in the first place. Sorry for the confusion What I actually looked for was the right setup for accelerated game animations done in Java. While reading through the suggestions I found my question answered (though indirectly) here and this example made things clear for me. A resume for this might be that for animating game graphics in Java, the first step is to get rid of the GUI logic overhead.

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• Margin-Top push outer div down

  - by Daniel Hertz

  Hello, I have a header div as the first element in my wrapper div, but when I add a top margin to a h1 inside the header div it pushes the entire header div down. I realize this happens whenever I apply a top margin to the first visible element on a page. Here is a sample of the css. Thanks! div#header{ width: 100%; background-color: #000; position: relative; } div#header h1{ text-align: center; width: 375px; height: 50px; margin: 0 auto; font-size: 220%; text-indent: -5000px; background: url('../../images/name_logo.png') no-repeat; } html part <div id="header"> <h1><a href="/home.php">Title</a></h1> <ul id="navbar">

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• Stable/repeatable random sort (MySQL, Rails)

  - by Matt Rogish

  I'd like to paginate through a randomly sorted list of ActiveRecord models (rows from MySQL database). However, this randomization needs to persist on a per-session basis, so that other people that visit the website also receive a random, paginate-able list of records. Let's say there are enough entities (tens of thousands) that storing the randomly sorted ID values in either the session or a cookie is too large, so I must temporarily persist it in some other way (MySQL, file, etc.). Initially I thought I could create a function based on the session ID and the page ID (returning the object IDs for that page) however since the object ID values in MySQL are not sequential (there are gaps), that seemed to fall apart as I was poking at it. The nice thing is that it would require no/minimal storage but the downsides are that it is likely pretty complex to implement and probably CPU intensive. My feeling is I should create an intersection table, something like: random_sorts( sort_id, created_at, user_id NULL if guest) random_sort_items( sort_id, item_id, position ) And then simply store the 'sort_id' in the session. Then, I can paginate the random_sorts WHERE sort_id = n ORDER BY position LIMIT... as usual. Of course, I'd have to put some sort of a reaper in there to remove them after some period of inactivity (based on random_sorts.created_at). Unfortunately, I'd have to invalidate the sort as new objects were created (and/or old objects being removed, although deletion is very rare). And, as load increases the size/performance of this table (even properly indexed) drops. It seems like this ought to be a solved problem but I can't find any rails plugins that do this... Any ideas? Thanks!!

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• How to have screen revert to BLACK between pages?

  - by user340667

  0 Hi - I tried out the Background Image Scaling script and with Cybr's update it works like magic. It SCALES the image perfectly. No distortion. BUT, my image isn't "computer friendly". I.e.: Not 1024 X 768 or even close to that. (Heck, my monitor has a wide screen, so it isn't 1024 X 768 either! Is anybody's anymore?) Anyhow, this creates a problem inasmuch as, unless I size the window from the bottom up it ends up with a white "stripe" beneath it. What I would REALLY like for it to do is have that white to be BLACK. My "usual" BG color/text etc. code is like: ""body bgcolor="#000000" text="#fcba1e" link="#0000ff" vlink="#800080" alink="#ff0000"" (Site won't let me add the arrows here.) I've tried inserting this in various places with no success. Any ideas for a workaround would surely be appreciated ! Thanks ! Bill

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• Aligning left and right in a simple footer

  - by Wolfram

  I'm currently working on a simple footer, and I would like to align one line of text left and the other to the right. This is what I have so far: <div id="footer"> Last Updated: October 15, 2012 <!--left align--> Contact Us Login <!--right align (these will be links)--> </div> #footer { font-family: Arial; font-size: .9em; color: #24ACAE; border-top: 1px solid #24ACAE; margin-left: 90px; margin-right: 90px; padding-top: 5px; } The above code results in the two lines of text being next to each other and I've tried various ways of fixing this such as putting the the 2nd line in a span and aligning right and even putting the lines into a table. None of what I have tried has resulted in both lines being properly aligned. Using a margin-left alone does not work because when the first line is updated and becomes longer, it will push the second line downwards. Relative positioning seems to have the same issue. Hopefully there's something simple that I'm overlooking.

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• Checking if user owns file before deleting it

  - by Martin Hoe

  I'm building an API for my site that allows users to delete the files they upload. Obviously, I want to check if the user owns that file before they delete it through the API. I have a files table and a users table, here's the schema: f_id, s_id, u_id, name, size, uploaded u_id, username, password, email, activated, activation_code u_id is a foreign key. The u_id field in the files table points to the u_id in the users table. Given the users username, I want to find the users u_id, and then check if they own the file through the file ID (f_id). I wrote this SQL: $sql = 'SELECT u.username FROM `users` u JOIN `files` f ON u.u_id = f.u_id WHERE f_id = ? AND u.u_id = ? LIMIT 1'; I'm assuming that'd work if I was given the users u_id in the API request, but alas I'm given only their username. How can I modify that SQL to find their user ID and use that? Thanks. Edit: Alright I've got this query but it's always returning an empty result set even though both the file ID and username exist. SELECT u.username FROM `users` u JOIN `files` f ON u.u_id = f.u_id WHERE f.f_id = ? AND u.username = ? LIMIT 1

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• Return the exact ID using fetch_assoc

  - by Selom

  Hi, I have a small problem in my code and I need your help. Well Im using fetch_assoc to get data from database and I need to get the ID number of each of returned values. the issue is that my code only return the ID number of the last data. Here's my code: <form method="post" action="action.php"> <select name="album" style="border:1px solid #CCC; font-size:11px; padding:1px"> <?php $sql = "SELECT * FROM table"; $stmt = $dbh -> prepare($sql); $stmt -> execute(); while($row = $stmt -> fetch(PDO::FETCH_ASSOC)) { $album_ID = $row['album_ID']; $value = $row['album_name']; print "<option value ='". $value ."'>". $value. "</option>"; } ?> </select> <input type="hidden" name="album_ID" value="<?php print $album_ID?>"/> </form> I would like the hidden input type holds the selected album id, but it always holds the album id of the last data. Please help.

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• Design for fastest page download

  - by mexxican

  I have a file with millions of URLs/IPs and have to write a program to download the pages really fast. The connection rate should be at least 6000/s and file download speed at least 2000 with avg. 15kb file size. The network bandwidth is 1 Gbps. My approach so far has been: Creating 600 socket threads with each having 60 sockets and using WSAEventSelect to wait for data to read. As soon as a file download is complete, add that memory address(of the downloaded file) to a pipeline( a simple vector ) and fire another request. When the total download is more than 50Mb among all socket threads, write all the files downloaded to the disk and free the memory. So far, this approach has been not very successful with the rate at which I could hit not shooting beyond 2900 connections/s and downloaded data rate even less. Can somebody suggest an alternative approach which could give me better stats. Also I am working windows server 2008 machine with 8 Gig of memory. Also, do we need to hack the kernel so as we could use more threads and memory. Currently I can create a max. of 1500 threads and memory usage not going beyond 2 gigs [ which technically should be much more as this is a 64-bit machine ]. And IOCP is out of question as I have no experience in that so far and have to fix this application today. Thanks Guys!

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• Efficient and accurate way to compact and compare Python lists?

  - by daveslab

  Hi folks, I'm trying to a somewhat sophisticated diff between individual rows in two CSV files. I need to ensure that a row from one file does not appear in the other file, but I am given no guarantee of the order of the rows in either file. As a starting point, I've been trying to compare the hashes of the string representations of the rows (i.e. Python lists). For example: import csv hashes = [] for row in csv.reader(open('old.csv','rb')): hashes.append( hash(str(row)) ) for row in csv.reader(open('new.csv','rb')): if hash(str(row)) not in hashes: print 'Not found' But this is failing miserably. I am constrained by artificially imposed memory limits that I cannot change, and thusly I went with the hashes instead of storing and comparing the lists directly. Some of the files I am comparing can be hundreds of megabytes in size. Any ideas for a way to accurately compress Python lists so that they can be compared in terms of simple equality to other lists? I.e. a hashing system that actually works? Bonus points: why didn't the above method work?

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• Filtering two arrays to avoid Inf/NaN values

  - by Gacek

  I have two arrays of doubles of the same size, containg X and Y values for some plots. I need to create some kind of protection against Inf/NaN values. I need to find all that pairs of values (X, Y) for which both, X and Y are not Inf nor NaN If I have one array, I can do it using lambdas: var filteredValues = someValues.Where(d=> !(double.IsNaN(d) || double.IsInfinity(d))).ToList(); Now, for two arrays I use following loop: List<double> filteredX=new List<double>(); List<double> filteredX=new List<double>(); for(int i=0;i<XValues.Count;i++) { if(!double.IsNan(XValues[i]) && !double.IsInfinity(XValues[i]) && !double.IsNan(YValues[i]) && !double.IsInfinity(YValues[i]) ) { filteredX.Add(XValues[i]); filteredY.Add(YValues[i]); } } Is there any way of filtering two arrays at the same time using LINQ/Lambdas, as it was done for single array?

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• Unexpected token ILLEGAL with jQuery

  - by Bram Vanroy

  So, I have a website with an autoFontSize script (Got it from stackoverflow, but slightly edited it too loop over each div with that specific class) (function ($) { $.fn.textfill = function (options) { this.each(function () { var fontSize = options.maxFontPixels; var ourText = $('h2 a', this); var maxHeight = $(this).height(); var maxWidth = $(this).width(); var textHeight; var textWidth; do { ourText.css('font-size', fontSize); textHeight = ourText.height(); textWidth = ourText.width(); fontSize = fontSize - 1; } while ((textHeight > maxHeight || textWidth > maxWidth) && fontSize > 16); }); return this; }; })(jQuery); $(document).ready(function () { $('.fotonode.fotopagina').textfill({ maxFontPixels: 30 }); });? And a (simplified) HTML structure: <div class="fotonode fotopagina"> <h2><a href="#">Testing Title</a></h2> </div> For some reason this doesn't work (neither locally nor live) BUT it does work on JSfiddle: http://jsfiddle.net/Yb9yj/ I read somewhere that this can cause problems. I copied the code from jsfiddle to my file, so maybe I have (unintentionally) copied some white spaces that shouldn't be there or something. I don't know. But how can I solve this then?

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• Long primitive or AtomicLong for a counter?

  - by Rich

  Hi I have a need for a counter of type long with the following requirements/facts: Incrementing the counter should take as little time as possible. The counter will only be written to by one thread. Reading from the counter will be done in another thread. The counter will be incremented regularly (as much as a few thousand times per second), but will only be read once every five seconds. Precise accuracy isn't essential, only a rough idea of the size of the counter is good enough. The counter is never cleared, decremented. Based upon these requirements, how would you choose to implement your counter? As a simple long, as a volatile long or using an AtomicLong? Why? At the moment I have a volatile long but was wondering whether another approach would be better. I am also incrementing my long by doing ++counter as opposed to counter++. Is this really any more efficient (as I have been led to believe elsewhere) because there is no assignment being done? Thanks in advance Rich

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• Creating a OS X Cocoa App Web View in Xcode 5.0.1

  - by user1822824

  I created a HTML5 web app that I’m trying to wrap in a web view and submit to the Mac App Store. I’ve done the following: 1) Opened Xcode 5.0.1 and selected “Create a new Xcode project” 2) Under “OS X” I selected “Application” then I selected “Cocoa Application” then “Next” 3) I entered a “Product Name” and a “Company Identifier” then selected “Next” (I left all the other settings untouched) then “Create” 4) Under “General” “Deployment Info” “Deployment Target” I selected 10.6 — because I want the app to be compatible with all versions of OS X that support the Mac App Store 5) I clicked “MainMenu.xib” and selected “Window - My App” 6) From the “Object library” I drug the “Web View” object into my window and made it fill the window size 7) I saved my project and click the Play button in the upper left corner of Xcode The app tries to open but freezes. I don’t get an error in Xcode but it does open “main.m” and highlight “return NSApplicationMain(argc, argv);” in green and says “Thread 1: signal SIGABRT” I was hoping that someone could clarify why this isn’t working? And provide me with the last step to link the web view object? I searched Google and found tutorials for iOS and a few for OS X but for different versions of Xcode.

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• Passing mix of T and T[] to a Java varargs method

  - by rfalke

  Suppose you have a Java method void foobar(int id, String ... args) and want to pass both String arrays and Strings into the method. Like this String arr1[]={"adas", "adasda"}; String arr2[]={"adas", "adasda"}; foobar(0, "adsa", "asdas"); foobar(1, arr1); foobar(2, arr1, arr2); foobar(3, arr1, "asdas", arr2); In Python there is "*" for this. Is there some way better than such rather ugly helper method: static String[] concat(Object... args) { List<String> result = new ArrayList<String>(); for (Object arg : args) { if (arg instanceof String) { String s = (String) arg; result.add(s); } else if (arg.getClass().isArray() && arg.getClass().getComponentType().equals(String.class)) { String arr[] = (String[]) arg; for (String s : arr) { result.add(s); } } else { throw new RuntimeException(); } } return result.toArray(new String[result.size()]); } which allows foobar(4, concat(arr1, "asdas", arr2));

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• Binding a TextBox's Width to its parent container's ActualWidth

  - by Praetorian

  Hi, I'm loading a Textbox and a Button into a horizontal StackPanel programmatically. The size of the button (which only contains an Image) is fixed, but I can't get the textbox to fill the available width of its parent. This is what the code looks like: StackPanel parent = new StackPanel() { Orientation = Orientation.Horizontal, HorizontalAlignment = HorizontalAlignment.Stretch, VerticalAlignment = VerticalAlignment.Top, }; TextBox textbox = new TextBox() { HorizontalAlignment = HorizontalAlignment.Stretch, VerticalAlignment = VerticalAlignment.Top, //MinWidth = 375, }; Button btn = new Button() { Content = new Image() { MaxHeight = 40, MaxWidth = 40, MinHeight = 40, MinWidth = 40, Margin = new Thickness( 0 ), Source = new BitmapImage( new Uri( "btnimage.png", UriKind.Relative ) ), }, HorizontalAlignment = HorizontalAlignment.Right, BorderBrush = new SolidColorBrush( Colors.Transparent ), Margin = new Thickness( 0 ), }; btn.Click += ( ( s, e ) => OnBtnClicked( s, e, textbox ) ); parent.Children.Add( textbox ); parent.Children.Add( btn ); If I uncomment the MinWidth setting for the textbox it is displayed as I want it to, but I'd like to not have to specify a width explicitly. I tried adding a binding as follows but that doesn't work at all (the textbox just disappears!) Binding widthBinding = new Binding() { Source = parent.ActualWidth, }; passwdBox.SetBinding( TextBox.WidthProperty, widthBinding ); Thanks for your help in advance!

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• How to add an object to a html string?

  - by Philippe Maes

  I'm trying to load several images by a drop action and than resizing them and adding them as a thumbnail. The resize part is very important because the images can be very large and I want to make the thumbnails small of size. Here is my code: loadingGif(drop); for (var i=0;i<files.length;i++) { var file = files[i]; var reader = new FileReader(); reader.onload = function(e) { var src = e.target.result; var img = document.createElement('img'); img.src = src; var scale = 100/img.height; img.height = 100; img.width = scale*img.width; output.push('<div id="imagecontainer"><div id="image">'+img+'</div><div id="delimage"><img src="img/del.jpg"" /></div></div>'); if(output.length == files.length) { drop.removeChild(drop.lastChild); drop.innerHTML += output.join(''); output.length = 0; } } reader.readAsDataURL(file); } As you can probably tell I insert a loading gif image in my dropzone until all files are loaded (output.length == files.length). When a file is loaded I add html to an array which I will print if the load is complete. The problem is I can't seem to add the img object (I need this object to resize the image) to the html string, which seems obvious as the img is an object... So my question to you guys is: how do I do this? :)

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• How to accommodate for the next iPhones totally different screen resolution?

  - by mystify

  This is a programming question! Read on before you vote to close! According to Gizmodo, the next iPhone will have a new screen resolution: The 3.5-inch screen has a resolution of 960?×?640 pixels This little detail affects our apps in a heavy way. Most of the demo apps on the net have one thing in common: They position views in the believe that the screen has a fixed size of 320 x 480 pixels. So what most -if not all- developers do is: They designed everything in such a way, that a touchable area is -for example- 50 x 50 pixels big. Just enough to tap it. Things have been positioned relative to the upper left, to reach a specific position on screen - let's say the center, or somewhere at the bottom. So the big question is: How will the developers compensate their layout and graphics? Are there already solutions which can be used to calculate coordinates and sizes in a normalized manner, which then appear to be exactly the same when viewing them on a screen of any resolution, assuming at least that the aspect ration won't change? This is community wiki. Just add anything that you think is relevant to this huge problem (constant screen res was one of the main reasons why I didn't go for Android!!).

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• Error in My Add button SQL Server Management Studio And Visual Basic 2010

  - by user2882523

  Here is the thing i cant use insert querry in my code there is an error in my sqlcommand that says the ExecuteNonQuery() not match with the values blah blah here is my code Dim con As New SqlClient.SqlConnection("Server=.\SQLExpress;AttachDBFilename=C:\Program Files\Microsoft SQL Server\MSSQL10_50.SQLEXPRESS\MSSQL\DATA\Finals.mdf;Database=Finals;Trusted_Connection=Yes;") Dim cmd As New SqlClient.SqlCommand cmd.Connection = con cmd.CommandText = "Insert Into [Finals].[dbo].[Nokia] Values ('" & Unit.Text & "'),('" & Price.Text & " '),('" & Stack.Text & "'),('" & Processor.Text & "'),('" & Size.Text & "'),('" & RAM.Text & "'),('" & Internal.Text & "'),('" & ComboBox1.Text & "')" con.Open() cmd.ExecuteNonQuery() con.Close() } the problem is the cmd.CommandText can anyone pls help me

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• Designing a different kind of tag cloud.

  - by animuson

  Rather than having a bunch of links that are all different sizes, I want all of my tags to be the same size. However, my goal is to minimize the amount of space required to make the cloud, aka minimizing the number of lines used. Take this example: Looks like any normal tag cloud. However, look at all that extra space around the 'roughdiamond' tag, which could be filled in by other tags like 'stone' down near the bottom, which could effectively eliminate an entire extra line from the cloud. How would I go about getting the words to fill in whatever space possible above them before starting a new line? I'm not talking about reorganizing them to find the absolute minimum number of lines required. If I was going through the list in the image, 'pendant', 'howlite', and 'igrice' would go to line 1 filling it up, 'roughdiamond' would go to line 2 because line 1 is full, 'tourmaline' would go to line 3 because it can't fit on lines 1 or 2, same with 'emberald', but 'pearl' would go to line 2 because it can fit there since there is extra space. I figure there would probably be some way of doing this in CSS that would simply cause the links to collapse into any fillable space it can fit in to.

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• Is it okay to rely on javascript for menu layout?

  - by Ryan

  I have a website template where I do not know the number of menu items or the size of the menu items that will be required. The js below works exactly the way I want it to, however this is the most js I've every written. Are there any disadvantages or potential problems with this method that I'm not aware of because I'm a js beginner? I'm currently manually setting the padding for each site. Thank you! var width_of_text = 0; var number_of_li = 0; // measure the width of each <li> and add it to the total with, increment li counter $('li').each(function() { width_of_text += $(this).width(); number_of_li++; }); // calculate the space between <li>'s so the space is equal var padding = Math.floor((900 - width_of_text)/(number_of_li - 1)); // add the padding the all but the first <li> $('li').each(function(index) { if (index !== 0) { $(this).css("padding-left", padding); } });

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• JavaScript library not working in IE, can't see error information.

  - by Wolfy87

  Hi there. I have been writing a JavaScript library for a few weeks now and it works brilliantly in Firefox, Chrome and Safari. I had not tested it in IE until recently. I do not own a Windows box so after testing it on my friends and realising it wasnt working I started going over my code for things that could be causing it to break. So far I have found nothing. I could not find any descriptions of the errors in the browser while I was there either. So I wondered if anyone could run my test script in an IE browser (6, 7 or 8) and let me know any information they can find as to why it crashed. Please ignore any information saying it works in IE6, I put that up there after testing it through http://ipinfo.info/netrenderer/ I just assumed it was working because I could set transparency and size via my script and see it run in this tool. Here is the link to my GitHub repository: https://github.com/Wolfy87/Spark If you download it and run spark.html it will attempt to run all of my functions from the library. So if anyone could be kind enough to run it in IE and either let me know what errors they are getting and possibly how to fix them then I will be extreamly grateful. Thank you in advance. EDIT: Here is it's website http://sparkjs.co.uk/

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• OCR combined with font recognition?

  - by Adam

  I have a bold idea where a user could take an image like the following and in a few seconds of processing, be able to edit a document which looks roughly the same. The software would use WhatTheFont (or something similar) to recognize the fonts used, and OCR and other software to handle the font size, color, line-spacing, and of course the text content itself. In the case of the example image, there would be three separate "textboxes" produced, each starting at the upper left corner of the text, and extending as far to the bottom right as it could before running into another text box. So the user would then see something like this: (The rectangles are just used to show the boundaries of each textbox.) From here, the user would be able to edit the text in each of these boxes to create a new document. Of course there are tons of obvious uses for such an application, especially on a mobile phone with a built in camera. So my questions are the following: I doubt the answer is yes, but does anything do this already? If I'm going to try to build this, what should I write it in? Can I use Python? What would be the best OCR libraries to start with? Is there a service other than WhatTheFont for font recognition that has better API support? Anybody want to help me build it? :) etc. etc. Update: One thing I wanted to mention (but forgot) is I would also like the background to be preserved. In other words, if the example above had an image behind the text, I'd like the document to use that image with text removed. I know this complicates things a lot because that would require some image editing techniques too (something akin to Photoshop CS5' "content-aware fill"). But if we can solve diminished reality on iPhones, I think we can figure this out!

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• How to encrypt a RSAKey using another RSAKey?

  - by Tom Brito

  I know its not the usual thing to do. But the specification I'm implementing is discribed this way, and I cannot run out. I was trying to encrypt the modulus and exponent of the private key, but the following test code raises an exception because the byte array is 1 byte larger then the maximum allowed by RSA block: import java.security.KeyPair; import java.security.KeyPairGenerator; import java.security.NoSuchAlgorithmException; import java.security.NoSuchProviderException; import java.security.interfaces.RSAPrivateKey; import java.security.interfaces.RSAPublicKey; import javax.crypto.Cipher; import org.apache.commons.lang.ArrayUtils; public class TEST { public static KeyPair generateKeyPair() throws NoSuchAlgorithmException, NoSuchProviderException { KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA", "BC"); keyPairGenerator.initialize(1024); return keyPairGenerator.generateKeyPair(); } public static void main(String[] args) throws Exception { KeyPair keyPair = generateKeyPair(); RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate(); System.out.println("Priv modulus len = " + privateKey.getModulus().bitLength()); System.out.println("Priv exponent len = " + privateKey.getPrivateExponent().bitLength()); System.out.println("Priv modulus toByteArray len = " + privateKey.getModulus().toByteArray().length); byte[] byteArray = privateKey.getModulus().toByteArray(); // the byte at index 0 have no value (in every generation it is always zero) byteArray = ArrayUtils.subarray(byteArray, 1, byteArray.length); System.out.println("byteArray size: " + byteArray.length); RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic(); Cipher cipher = Cipher.getInstance("RSA", "BC"); cipher.init(Cipher.ENCRYPT_MODE, publicKey); byte[] encryptedBytes = cipher.doFinal(byteArray); System.out.println("Success!"); } } (obs. its just a test, i would never encrypt the private key with its pair public key) The byte array is 128 bytes, the exactly maximum allowed by a RSA block, so why the exception? And how to fix it?

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