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  • Bandpass filter of FFT applied image. (Like ImageJ bandpass filter algorithm)

    - by maximus
    There is a good function that I need, which is implemented in Java program: ImageJ I need to understand the algorithm used there. The function has several parameters: link text And before using FFT it converts image to a special one: The Bandpass Filter uses a special algorithm to reduce edge artifacts (before the Fourier transform, the image is extended in size by attaching mirrored copies of image parts outside the original image, thus no jumps occur at the edges) Can you tell me more about this special transform? Actually tiling mirrored image. I am writing on C++ and wish to rewrite that part of the program on C++.

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  • Cilk or Cilk++ or OpenMP

    - by Aman Deep Gautam
    I'm creating a multi-threaded application in Linux. here is the scenario: Suppose I am having x instance of a class BloomFilter and I have some y GB of data(greater than memory available). I need to test membership for this y GB of data in each of the bloom filter instance. It is pretty much clear that parallel programming will help to speed up the task moreover since I am only reading the data so it can be shared across all processes or threads. Now I am confused about which one to use Cilk, Cilk++ or OpenMP(which one is better). Also I am confused about which one to go for Multithreading or Multiprocessing

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  • Is there a function that can read a php function post-parsing?

    - by Rob
    I've got a php file echoing hashes from a MySQL database. This is necessary for a remote program I'm using, but at the same time I need my other php script opening and checking it for specified strings POST parsing. If it checks for the string pre-parsing, it'll just get the MySQL query rather than the strings to look for. I'm not sure if any functions do this. Does fopen() read the file prior to parsing? or file_get_contents()? If so, is there a function that'll read the file after the php and mysql code runs? The file with the hashes query and echo is in the same directory as the php file reading it, if that makes a difference. Perhaps fopen reads it post-parse, and I've done something wrong, but at first I was storing the hashes directly in the file, and it was working fine. After I changed it to echo the contents of the MySQL table, it bugged out.

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  • Detecting Markers Using OpenCV

    - by Hamza Yerlikaya
    I am trying to detect various objects containing colored markers, so a red blue green marker identifies object A, and a red blue red marker identifies object B. My problem is I can't use template matching cause objects can be rotated, currently I am thinking about check for each color then find the object by checking the distance between colors but it seems inefficient, so my question is there a better way to do this?

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  • Why Doesn't This Java Code Skip Lines with #?

    - by Nathan
    I'm trying to allow an external .txt file that is read by a Java script be able to have some comments in the beginning of the file so others can easily edit it and add more to it. But if the file contains # (the sign designated for a line that is a comment) it just returns the error that there is a "Format Error in file" (the IOException - so it is getting past that first "IF"...) Can someone help? Here's the portion of the code that deals with commenting lines out of the .txt file being called earlier in the script: while ((line = br.readLine()) != null) { line = line.trim(); if (line.length() < 1 || line.charAt(0) == '#') { // ignore comments continue; } final String[] parts = line.split("="); if (parts.length != 2) { throw new IOException("Format error in file " + JLanguageTool.getDataBroker().getFromRulesDirAsUrl(getFileName()) + ", line: " + line); }

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  • Thresholding in Matlab

    - by 3babala
    How do I threshold an image to find the local maxes in a robust way? I know I can just look at the data, visually guess at some appropriate h value, and do imextendedmax(I,h) where h is the threshold... but I'm looking for a more robust way to do it in Matlab. I'm pretty new to Matlab and coding so this is all foreign...

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  • How to detect circles accurately

    - by user1767798
    Is there any way to accurately detect circles in opencv? I was using hough transform which give me good result but most of the time, shadow of the object and surrounding,light etc gives bad results, so am looking for options other than hough circles, accurate detection is very important for my project. My basic approach so far is to find some spheres in the image taken in realtime. I am using houghcircle to find the spheres and base later calculations on the radius I am getting from that. If the background is plain and nothing the sphere detect without problem, however if I am taking that image in my room where the background will have other objects it's often difficult to detect. So am looking for some other approach.

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  • How to process audio in real time?

    - by user1756648
    I am giving some audio input through microphone. I recorded it in Audacity, it looks something like as shown below. I want to process this audio in real time. I mainly want to do this. 1) see real time audio amplitude vs time graph 2) perform some actions based on some thing (like if a specific type of hike is seen in audio, then do something, else do something else) Is there any python module or C library that can allow me to do this ?

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  • Codeigniter Image Library Cropping an Image with 2 sets of coordinates to make square anywhere?

    - by chris
    Spending time reading through the docs, and searching for examples. I understand cropping an image from top 0, and left 0 is pretty straight forward. However. I would like to pass 2 sets of coordinates, a starting point and an ending point. Four Points, a Square that is defined anywhere. However from the examples I am finding, and from what I gather the rendition is not going to let me do this. codeigniter so I am seeking confirmation on this thought, is it true that I can only provide end points from 0, and it crops a square based on said end points or can I actually specify an x start, an x end, and similar for y? Or is there some other technique I can use within codeigniter that will allow me to pass for coordinates for starting and ending points?

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  • Standardizing camera input in OpenCV? (Contrast/Saturation/Brightness etc..)

    - by karpathy
    I am building an application using OpenCV that uses the webcam and runs some vision algorithms. I would like to make this application available on the internet after I am done, but I am concerned about the vast differences in camera settings on every computer, and I am worried that the algorithm may break if the settings are too different from mine. Is there any way, after capturing the frame, to post process it and make sure that the contrast is X, brightness is Y, and saturation is Z? I think the Camera settings themselves can not be changed from code directly using the current OpenCV Python bindings. Would anyone be able to tell me about how I could calculate some of these parameters from the image and adjust them appropriately using OpenCV?

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  • Java - Robot keyPress issue

    - by Trimbitas Sorin
    I'm trying to send keystrokes (like a virtual keyboard) from my Java code, but I encounter some issues. It works perfectly on normal applications (for example, Notepad, browsers, etc.), but not on games (fullscreen or windowed mode). This is the stripped code I'm using: import java.awt.Robot; import java.awt.AWTException; import java.awt.event.InputEvent; Robot robot; robot.keyPress(KeyEvent.VK_A); robot.keyRelease(KeyEvent.VK_A); How can this problem be fixed?

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  • Downloading large file with php

    - by Alessandro
    Hi, I have to write a php script to download potentially large files. The file I'm reporting here works fine most of the times. However, if the client's connection is slow the request ends (with status code 200) in the middle of the downloading, but not always at the very same point, and not at the very same time. I tried to overwrite some php.ini variables (see the first statements) but the problem remains. I don't know if it's relevant but my hosting server is SiteGround, and for simple static file requests, the download works fine also with slow connections. I've found Forced downloading large file with php but I didn't understand mario's answer. I'm new to web programming. So here's my code. <?php ini_set('memory_limit','16M'); ini_set('post_max_size', '30M'); set_time_limit(0); include ('../private/database_connection.php'); $downloadFolder = '../download/'; $fileName = $_POST['file']; $filePath = $downloadFolder . $fileName; if($fileName == NULL) { exit; } ob_start(); session_start(); if(!isset($_SESSION['Username'])) { // or redirect to login (remembering this download request) $_SESSION['previousPage'] = 'download.php?file=' . $fileName; header("Location: login.php"); exit; } if (file_exists($filePath)) { header('Content-Description: File Transfer'); header('Content-Type: application/octet-stream'); //header('Content-Disposition: attachment; filename='.$fileName); header("Content-Disposition: attachment; filename=\"$fileName\""); header('Content-Transfer-Encoding: binary'); header('Expires: 0'); header('Cache-Control: must-revalidate, post-check=0, pre-check=0'); //header('Pragma: public'); header('Content-Length: ' . filesize($filePath)); ob_clean(); flush(); // download // 1 // readfile($filePath); // 2 $file = @fopen($filePath,"rb"); if ($file) { while(!feof($file)) { print(fread($file, 1024*8)); flush(); if (connection_status()!=0) { @fclose($file); die(); } } @fclose($file); } exit; } else { header('HTTP/1.1 404 File not found'); exit; } ?>

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  • What's the fastest way to approximate the period of data using Octave?

    - by John
    I have a set of data that is periodic (but not sinusoidal). I have a set of time values in one vector and a set of amplitudes in a second vector. I'd like to quickly approximate the period of the function. Any suggestions? Specifically, here's my current code. I'd like to approximate the period of the vector x(:,2) against the vector t. Ultimately, I'd like to do this for lots of initial conditions and calculate the period of each and plot the result. function xdot = f (x,t) xdot(1) =x(2); xdot(2) =-sin(x(1)); endfunction x0=[1;1.75]; #eventually, I'd like to try lots of values for x0(2) t = linspace (0, 50, 200); x = lsode ("f", x0, t) plot(x(:,1),x(:,2)); Thank you! John

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  • head detection from video

    - by Aman Kaushal
    I have to detect heads of people in crowd in real time.For that I detected edge from video using matlab but from edge detected video , how to identify heads that i am unable to do. I used edge detection of video because it is easy to find circle from edged video and detection of head would be easy can anyone help me or suggest me any method for head- detection in real time. I have used VGG head detector and viola jones algorithm but it is only detecting face for small size video not detecting heads for large crowd. Suggestions?

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  • Subtract displaced mask using OpenCV

    - by dario_ramos
    I want to do: masked = image - mask But I want to "displace" mask. That is, move it vertically and horizontally (as long as the intersection between it and image is not empty, this would be valid). I have some hand-coded assembly (which uses MMX instructions) which does this, embedded in a C++ program, but it's unstable when doing vertical displacemente, so I thought of using OpenCV instead. Would it be possible to do this calling only one OpenCV function? Performance is critical; using OpenCV, time should be at least in the same order of magnitude as the assembly code.

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  • How to do motion tracking of a object using video

    - by Niroshan
    Could someone direct me to a tutorial or guide me how to track motion of a object moving with 6 DOF. I am planing to use a video stream of a moving toy car. I want to calculate displacement and rotation angle of the toy car. I came across some research papers but couldn't find any libraries to the job. Is there a way to do this using OpenCV or Matlab or some other freely available software? Thank you

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  • Windows Azure: Parallelization of the code

    - by veda
    I have some matrix multiplication operation. I want to parallelize the execution of those operations through multiple processors.. This can be done on high performance computing cluster using MPI (Message Passing Interface). Like wise, can I do some parallelization in the cloud using multiple worker roles. Is there any means for doing that.

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  • Why is PLINQ slower than LINQ for this code?

    - by Rob Packwood
    First off, I am running this on a dual core 2.66Ghz processor machine. I am not sure if I have the .AsParallel() call in the correct spot. I tried it directly on the range variable too and that was still slower. I don't understand why... Here are my results: Process non-parallel 1000 took 146 milliseconds Process parallel 1000 took 156 milliseconds Process non-parallel 5000 took 5187 milliseconds Process parallel 5000 took 5300 milliseconds using System; using System.Collections.Generic; using System.Diagnostics; using System.Linq; namespace DemoConsoleApp { internal class Program { private static void Main() { ReportOnTimedProcess( () => GetIntegerCombinations(), "non-parallel 1000"); ReportOnTimedProcess( () => GetIntegerCombinations(runAsParallel: true), "parallel 1000"); ReportOnTimedProcess( () => GetIntegerCombinations(5000), "non-parallel 5000"); ReportOnTimedProcess( () => GetIntegerCombinations(5000, true), "parallel 5000"); Console.Read(); } private static List<Tuple<int, int>> GetIntegerCombinations( int iterationCount = 1000, bool runAsParallel = false) { IEnumerable<int> range = Enumerable.Range(1, iterationCount); IEnumerable<Tuple<int, int>> integerCombinations = from x in range from y in range select new Tuple<int, int>(x, y); return runAsParallel ? integerCombinations.AsParallel().ToList() : integerCombinations.ToList(); } private static void ReportOnTimedProcess( Action process, string processName) { var stopwatch = new Stopwatch(); stopwatch.Start(); process(); stopwatch.Stop(); Console.WriteLine("Process {0} took {1} milliseconds", processName, stopwatch.ElapsedMilliseconds); } } }

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  • Parallel software?

    - by mavric
    What is the meaning of "parallel software" and what are the differences between "parallel software" and "regular software"? What are its advantages and disadvantages? Does writing "parallel software" require a specific hardware or programming language ?

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  • Problem with thumbnails after newly added - PHP on-the-fly method

    - by Wayne
    Hey again... to those that may have read my previous question that got solved a couple minutes ago .< The on-the-fly php script works perfectly, but when I went to upload new images into a gallery which I made myself, the images are resized to 150 x 150 for what I wanted... however, when it comes to new images being added it is all black... As you can see the three black images that were uploaded to the folder and the directory added to the database. What is causing this? If I view the source, the code is fine... the while loop in the PHP generates an output like this: <div class="view-wrap" id="photo-10"> <div class="view-icon"> <div class="img-label"> <a href="#" id="10" class="delete"><img src="img/small-delete.png" /> Delete</a> </div> <a href="img/events/Paintballing/24251_1395408043148_1170626626_1204038_5382765_n.jpg"> <img src="image.php?dir=img/events/Paintballing/24251_1395408043148_1170626626_1204038_5382765_n.jpg" alt="" width="110" height="110" /> </a> </div> </div> An example of one block. If I view the source (in Firefox) and click on the image.php?dir=img/events/Paintballing/24251_1395408043148_1170626626_1204038_5382765_n.jpg by exmaple, I can see the thumbnail at it's 150 x 150 size but in the layout, it shows a black thumbnail... Does anyone know why this is happening?

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