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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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• 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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• 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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• 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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• How can I implement this visual effect in MATLAB?

  - by user198729

  One can use Google's logo for a try: BTW, what's the term for it?

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• Why does using the Asynchronous Programming Model in .Net not lead to StackOverflow exceptions?

  - by uriDium

  For example, we call BeginReceive and have the callback method that BeginReceive executes when it has completed. If that callback method once again calls BeginReceive in my mind it would be very similar to recursion. How is that this does not cause a stackoverflow exception. Example code from MSDN: private static void Receive(Socket client) { try { // Create the state object. StateObject state = new StateObject(); state.workSocket = client; // Begin receiving the data from the remote device. client.BeginReceive( state.buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(ReceiveCallback), state); } catch (Exception e) { Console.WriteLine(e.ToString()); } } private static void ReceiveCallback( IAsyncResult ar ) { try { // Retrieve the state object and the client socket // from the asynchronous state object. StateObject state = (StateObject) ar.AsyncState; Socket client = state.workSocket; // Read data from the remote device. int bytesRead = client.EndReceive(ar); if (bytesRead > 0) { // There might be more data, so store the data received so far. state.sb.Append(Encoding.ASCII.GetString(state.buffer,0,bytesRead)); // Get the rest of the data. client.BeginReceive(state.buffer,0,StateObject.BufferSize,0, new AsyncCallback(ReceiveCallback), state); } else { // All the data has arrived; put it in response. if (state.sb.Length > 1) { response = state.sb.ToString(); } // Signal that all bytes have been received. receiveDone.Set(); } } catch (Exception e) { Console.WriteLine(e.ToString()); } }

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• Parallel Haskell in order to find the divisors of a huge number

  - by Dragno

  I have written the following program using Parallel Haskell to find the divisors of 1 billion. import Control.Parallel parfindDivisors :: Integer->[Integer] parfindDivisors n = f1 `par` (f2 `par` (f1 ++ f2)) where f1=filter g [1..(quot n 4)] f2=filter g [(quot n 4)+1..(quot n 2)] g z = n `rem` z == 0 main = print (parfindDivisors 1000000000) I've compiled the program with ghc -rtsopts -threaded findDivisors.hs and I run it with: findDivisors.exe +RTS -s -N2 -RTS I have found a 50% speedup compared to the simple version which is this: findDivisors :: Integer->[Integer] findDivisors n = filter g [1..(quot n 2)] where g z = n `rem` z == 0 My processor is a dual core 2 duo from Intel. I was wondering if there can be any improvement in above code. Because in the statistics that program prints says: Parallel GC work balance: 1.01 (16940708 / 16772868, ideal 2) and SPARKS: 2 (1 converted, 0 overflowed, 0 dud, 0 GC'd, 1 fizzled) What are these converted , overflowed , dud, GC'd, fizzled and how can help to improve the time.

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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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• 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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• Invalid Cross-Thread Operations from BackgroundWorker2_RunWorkerCompleted in C#

  - by Jim Fell

  Hello. I'm getting an error that does not make sense. Cross-thread operation not valid: Control 'buttonOpenFile' accessed from a thread other than the thread it was created on. In my application, the UI thread fires off backgroundWorker1, which when almost complete fires off backgroundWorker2 and waits for it to complete. backgroundWorker1 waits for backgroundWorker2 to complete, before it completes. AutoResetEvent variables are used to flag when each of the workers complete. In backgroundWorker2_RunWorkerComplete a function is called that resets the form controls. It is in this ResetFormControls() function where the exception is thrown. I thought it was safe to modify form controls in the RunWorkerCompleted function. Both background workers are instantiated from the UI thread. Here is a greatly summarized version of what I am doing: AutoResetEvent evtProgrammingComplete_c = new AutoResetEvent(false); AutoResetEvent evtResetComplete_c = new AutoResetEvent(false); private void ResetFormControls() { toolStripProgressBar1.Enabled = false; toolStripProgressBar1.RightToLeftLayout = false; toolStripProgressBar1.Value = 0; buttonInit.Enabled = true; buttonOpenFile.Enabled = true; // Error occurs here. buttonProgram.Enabled = true; buttonAbort.Enabled = false; buttonReset.Enabled = true; checkBoxPeripheryModule.Enabled = true; checkBoxVerbose.Enabled = true; comboBoxComPort.Enabled = true; groupBoxToolSettings.Enabled = true; groupBoxNodeSettings.Enabled = true; } private void buttonProgram_Click(object sender, EventArgs e) { while (backgroundWorkerProgram.IsBusy) backgroundWorkerProgram.CancelAsync(); backgroundWorkerProgram.RunWorkerAsync(); } private void backgroundWorkerProgram_DoWork(object sender, DoWorkEventArgs e) { // Does a bunch of stuff... if (tProgramStat_c == eProgramStat_t.DONE) { tProgramStat_c = eProgramStat_t.RESETTING; while (backgroundWorkerReset.IsBusy) backgroundWorkerReset.CancelAsync(); backgroundWorkerReset.RunWorkerAsync(); evtResetComplete_c.WaitOne(LONG_ACK_WAIT * 2); if (tResetStat_c == eResetStat_t.COMPLETED) tProgramStat_c = eProgramStat_t.DONE; } } private void backgroundWorkerProgram_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) { // Updates form to report complete. No problems here. evtProgrammingComplete_c.Set(); backgroundWorkerProgram.Dispose(); } private void backgroundWorkerReset_DoWork(object sender, DoWorkEventArgs e) { // Does a bunch of stuff... if (tResetStat_c == eResetStat_t.COMPLETED) if (tProgramStat_c == eProgramStat_t.RESETTING) evtProgrammingComplete_c.WaitOne(); } private void backgroundWorkerReset_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) { CloseAllComms(); ResetFormControls(); evtResetComplete_c.Set(); backgroundWorkerReset.Dispose(); } Any thoughts or suggestions you may have would be appreciated. I am using Microsoft Visual C# 2008 Express Edition. Thanks.

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• Threshold of blurry image - part 2

  - by 1''

  How can I threshold this blurry image to make the digits as clear as possible? In a previous post, I tried adaptively thresholding a blurry image (left), which resulted in distorted and disconnected digits (right): Since then, I've tried using a morphological closing operation as described in this post to make the brightness of the image uniform: If I adaptively threshold this image, I don't get significantly better results. However, because the brightness is approximately uniform, I can now use an ordinary threshold: This is a lot better than before, but I have two problems: I had to manually choose the threshold value. Although the closing operation results in uniform brightness, the level of brightness might be different for other images. Different parts of the image would do better with slight variations in the threshold level. For instance, the 9 and 7 in the top left come out partially faded and should have a lower threshold, while some of the 6s have fused into 8s and should have a higher threshold. I thought that going back to an adaptive threshold, but with a very large block size (1/9th of the image) would solve both problems. Instead, I end up with a weird "halo effect" where the centre of the image is a lot brighter, but the edges are about the same as the normally-thresholded image: Edit: remi suggested morphologically opening the thresholded image at the top right of this post. This doesn't work too well. Using elliptical kernels, only a 3x3 is small enough to avoid obliterating the image entirely, and even then there are significant breakages in the digits:

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• How to decide between using PLINQ and LINQ at runtime?

  - by Hamish Grubijan

  Or decide between a parallel and a sequential operation in general. It is hard to know without testing whether parallel or sequential implementation is best due to overhead. Obviously it will take some time to train "the decider" which method to use. I would say that this method cannot be perfect, so it is probabilistic in nature. The x,y,z do influence "the decider". I think a very naive implementation would be to give both 1/2 chance at the beginning and then start favoring them according to past performance. This disregards x,y,z, however. I suspect that this question would be better answered by academics than practitioners. Anyhow, please share your heuristic, your experience if any, your tips on this. Sample code: public interface IComputer { decimal Compute(decimal x, decimal y, decimal z); } public class SequentialComputer : IComputer { public decimal Compute( ... // sequential implementation } public class ParallelComputer : IComputer { public decimal Compute( ... // parallel implementation } public class HybridComputer : IComputer { private SequentialComputer sc; private ParallelComputer pc; private TheDecider td; // Helps to decide between the two. public HybridComputer() { sc = new SequentialComputer(); pc = new ParallelComputer(); td = TheDecider(); } public decimal Compute(decimal x, decimal y, decimal z) { decimal result; decimal time; if (td.PickOneOfTwo() == 0) { // Time this and save result into time. result = sc.Compute(...); } else { // Time this and save result into time. result = pc.Compute(); } td.Train(time); return result; } }

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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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• How to implement async pattern in windows forms application?

  - by Alkersan

  I'm using an MVC pattern in winforms application. I need to call remote service asynchronously. So On some event in View I invoke corresponding Presenter method. In Presenter I call BeginInvoke method of service. But to View must be updated only in Main Thread. I could actualy point CallBack to some function in View, and update it`s controls state, but this conflicts with MVP pattern - View must not be responsible for data it carries. This callback function must be in Presenter. But how then invoke View in Main Thread?

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• BlackBerry Technical Specification

  - by Sam

  I'm having trouble locating BlackBerry techical specifications and their website is a mess. They also don't have a number that I can use to easily contact them. This isn't exactly a coding question, but what does the BlackBerry audio API look like, and where can I get technical specifications on audio? Specifically, I'm trying to find out more information on Audio-In, specifically, through the Mic-In on the 3.5 mm jack. Unfortunately, before I can proceed, I need to know such things like sampling rate, data width, etc. Direction to the right resource or if you know off of the top of your head is appreciated.

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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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• 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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• Resizing an image with alpha channel

  - by Hafthor

  I am writing some code to generate images - essentially I have a source image that is large and includes transparent regions. I use GDI+ to open that image and add additional objects. What I want to do next is to save this new image much smaller, so I used the Bitmap constructor that takes a source Image object and a height and width, then saved that. I was expecting the alpha channel to be smoothed like the color channels, but this did not happen -- it did result in a couple of semitransparent pixels, but overall it is very blocky. What gives? Using img As New Bitmap("source100x100.png") ''// Drawing stuff Using simg As New Bitmap(img, 20, 20) simg.Save("target20x20.png") End Using End Using Edit: I think what I want is SuperSampling, like what Paint.NET does when set to "Best Quality"

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• Read PPM Images in C

  - by rpf

  Hello!! Does anyone knows how can I read a PPM image into an array using C? Thanks. Best regards.

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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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• Video encoding by servlet with MEncoder

  - by Andrey

  Hello. I was developing an application for video encoding on the server and got a problem with encoding video with MEncoder. This decoder doesn't work correctly when runned by a command line with Runtime.getRuntime().exec(“D:\mencoder\mnc\mencoder.exe video1.avi -o outvideo1.flv -of lavf -oac mp3lame -lameopts abr:br=64 -srate 22050 -ovc lavc -lavcopts vcodec=flv:vbitrate=300:mbd=2:mv0:trell:v4mv:cbp:last_pred=3 -vf scale=320:240,harddup -quiet”) ; The decoder launches and works in windows console with my parameters, but when it's run from a servlet it just hangs in process list and doesn't do anything before the web-server is stopped. When trying to use decoder from a simple java applcation, it runs correctly. Thanks for help.

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• Aligning multiple images into one image?

  - by Gerald Kaszuba

  What is a good method to align images together that may have different rotations, exposures, etc, but have the same background or other fixed reference? Adobe Photoshop can do this with its "Photomerge" feature. How can I do this programatically? Is there an Open Source application that does it?

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• Pros and cons of keeping metadata in image thumbnails

  - by SODA

  I am working on optimizing site load speed for a few moderately high traffic sites. Some quick observations show that creating 40 picture thumbnails (e.g. 138x138 JPG @75% quality) results in 700 Kb total size with embedded metadata and 258 Kb with stripped metadata. Which means that roughly 60% of image size is metadata. So what would be pros and cons of removing metadata from thumbnails? Are there any regulations, e.g. you must keep author info / copyright info in the images? Any insights would be appreciated.

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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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