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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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  • 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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  • 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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  • 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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  • 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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  • How can I merge two Linq IEnumerable<T> queries without running them?

    - by makerofthings7
    How do I merge a List<T> of TPL-based tasks for later execution? public async IEnumerable<Task<string>> CreateTasks(){ /* stuff*/ } My assumption is .Concat() but that doesn't seem to work: void MainTestApp() // Full sample available upon request. { List<string> nothingList = new List<string>(); nothingList.Add("whatever"); cts = new CancellationTokenSource(); delayedExecution = from str in nothingList select AccessTheWebAsync("", cts.Token); delayedExecution2 = from str in nothingList select AccessTheWebAsync("1", cts.Token); delayedExecution = delayedExecution.Concat(delayedExecution2); } /// SNIP async Task AccessTheWebAsync(string nothing, CancellationToken ct) { // return a Task } I want to make sure that this won't spawn any task or evaluate anything. In fact, I suppose I'm asking "what logically executes an IQueryable to something that returns data"? Background Since I'm doing recursion and I don't want to execute this until the correct time, what is the correct way to merge the results if called multiple times? If it matters I'm thinking of running this command to launch all the tasks var AllRunningDataTasks = results.ToList(); followed by this code: while (AllRunningDataTasks.Count > 0) { // Identify the first task that completes. Task<TableResult> firstFinishedTask = await Task.WhenAny(AllRunningDataTasks); // ***Remove the selected task from the list so that you don't // process it more than once. AllRunningDataTasks.Remove(firstFinishedTask); // TODO: Await the completed task. var taskOfTableResult = await firstFinishedTask; // Todo: (doen't work) TrustState thisState = (TrustState)firstFinishedTask.AsyncState; // TODO: Update the concurrent dictionary with data // thisState.QueryStartPoint + thisState.ThingToSearchFor Interlocked.Decrement(ref thisState.RunningDirectQueries); Interlocked.Increment(ref thisState.CompletedDirectQueries); if (thisState.RunningDirectQueries == 0) { thisState.TimeCompleted = DateTime.UtcNow; } }

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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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  • 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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  • Basic FreeMat/MATLAB syntax - dimension error

    - by 0x90
    I am using FreeMat, and I have an RGB picture which is a 3D matrix contains the columns and rows of the pictures and the RGB values for each pixel. Since there is not an intrinsic function to convert RGB picture to YIQ, I have implement one. I came up with this code: Assume I have a 3D array, image_rgb: matrix = [0.299 0.587 0.114; 0.596 -0.274 -0.322; 0.211 -0.523 0.312]; row = 1:length(image_rgb(:,1,1)); col = 1:length(image_rgb(1,:,1)); p = image_rgb(row,col,:); %Here I have the problem mage_yiq(row,col,:) = matrix*image_rgb(row,col,:); max_y = max (max(image_yiq(:,:,1))); max_i = max (max(image_yiq(:,:,2))); max_q = max (max(image_yiq(:,:,3))); %Renormalize the image again after the multipication % to [0,1]. image_yiq(:,:,1) = image_yiq(:,:,1)/max_y; image_yiq(:,:,2) = image_yiq(:,:,2)/max_i; image_yiq(:,:,3) = image_yiq(:,:,3)/max_q; I can't understand why the matrix multiplication fails. I want the code to be nice and not just to, multiply the matrix by hand...

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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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  • 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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  • Image size guidelines

    - by user502014
    Hi all, This may well be a little of an open-ended question The site I am working on requires to be optimised for performance. One of the key areas is to optimise the file sizes of the images used upon the site. Unfortunatley these images are being created by employees who do not have the required knowledge for creating images for the web, and it is my job to produce a set of guidelines for them to use. I was wondering whether there was any resource/guidlines/literature regarding typical images file sizes for images of different dimensions - as I would like to include something like this to aid them to ensure their images are being created properly. Any info would be greatly appreciated. Thanks in advance

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  • Opencv video frame not showing Sobel output

    - by user1016950
    This is a continuation question from Opencv video frame giving me an error I think I closed it off, Im new to Stackoverflow. I have code below that Im trying to see its Sobel edge image. However the program runs but the output is just a grey screen where if I mouseover the cursor disappears. Does anyone see the error? or is it a misunderstanding about the data structures Im using IplImage *frame, *frame_copy = 0; // capture frames from video CvCapture *capture = cvCaptureFromFile( "lightinbox1.avi"); //Allows Access to video propertys cvQueryFrame(capture); //Get the number of frames int nframe=(int) cvGetCaptureProperty(capture,CV_CAP_PROP_FRAME_COUNT); //Name window cvNamedWindow( "video:", 1 ); //start loop for(int i=0;i<nframe;i++){ //prepare capture frame extraction cvGrabFrame(capture); cout<<"We are on frame "<<i<<"\n"; //Get this frame frame = cvRetrieveFrame( capture ); con2txt(frame); frame_copy = cvCreateImage(cvSize(frame->width,frame->height),IPL_DEPTH_8U,frame->nChannels ); //show and destroy frame cvCvtColor( frame,frame,CV_RGB2GRAY); //Create Sobel output frame_copy1 = cvCreateImage(cvSize(frame->width,frame->height),IPL_DEPTH_16S,1 ); cvSobel(frame_copy,frame_copy1,2,2,3); cvShowImage("video:",frame_copy1); cvWaitKey(33);} cvReleaseCapture(&capture);

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  • Subdomain forwarding using .htaccess

    - by RJ
    I want to redirect a praticular subdomain to the main domain http(s)://dl.example.com/par1/par2 to http(s)://www.example.com/par1/par2 How to achieve the above using .htaccess Why i want to do this: Whenever any user download a file from my server, if the file is huge , then user cannot do any other operation until the file is downloaded completely...so the solution that i have thought is to forward the download request through subdomain so that the browser may continue with rest of the operation. Thanks

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  • Identifying idle state on a windows machine

    - by SaM
    I know about the GetLastInputInfo method but that would only give me the duration since last user input - keyboard or mouse. If a user input was last received 10 minutes ago, that wouldn't mean the system has been idle for 10 minutes - scans, downloads, movies - lots of reasons. So how can we identify whether the system is truly idle or not? Does anyone know what Window's definition of "idle" is? Must be a combination of thresholds - like less than 5% cpu util, less than 3% disk util etc. - along with the user input parameter...anyone knows the exact definition?

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  • Parallelizing a serial algorithm

    - by user643813
    Hej folks, I am working on porting a Text mining/Natural language application from single-core to a Map-Reduce style system. One of the steps involves a while loop similar to this: Queue<Element>; while (!queue.empty()) { Element e = queue.next(); Set<Element> result = calculateResultSet(e); if (!result.empty()) { queue.addAll(result); } } Each iteration depends on the result of the one before (kind of). There is no way of determining the number of iterations this loop will have to perform. Is there a way of parallelizing a serial algorithm such as this one? I am trying to think of a feedback mechanism, that is able to provide its own input, but how would one go about parallelizing it? Thanks for any help/remarks

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  • Which is the best way to encode batch videos on server side?

    - by albanx
    Hello I am making a general question since I am a developer and I have no advance experience on video elaboration. I have to preparare a web application with the purpose to allow video files upload on our company server and then video elaboration by server, on user command. The purpose of the web application is to allow to the user to make some elaboration on video depending on user action launch from the web app: (server has to ) convert video in different format(mp4, flv...) extact keyframes from video and saves them in jpeg format possibility to extract audio from video automatic control of quality audio & video (black frames,silences detection) change scene detection and keyframe extraction ..... This what's my bosses wanted from the web based application (with the server support obviously), and I understand only the first 3 points of this list, the rest for me was arabic.... My question is: Which is the best and fastest server side application for this works, that can support multiple batch video conversions, from command line (comand line for php-soap-socket interaction or something else..)? Is suitable Adobe Media Server for batch video conversion? Which are adobe products that can be used for this purpose? Note: I have experience with Indesign Server scripting programing (sending xml with php and soap call...), and I am looking to something similiar for video elaboration. I will appreciate any answers. THANKS ALL

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  • C# Combining lines

    - by Mike
    Hey everybody, this is what I have going on. I have two text files. Umm lets call one A.txt and B.txt. A.txt is a config file that contains a bunch of folder names, only 1 listing per folder. B.txt is a directory listing that contains folders names and sizes. But B contains a bunch of listing not just 1 entry. What I need is if B, contains A. Take all lines in B that contain A and write it out as A|B|B|B ect.... So example: A.txt: Apple Orange Pear XBSj HEROE B.txt: Apple|3123123 Apple|3434 Orange|99999999 Orange|1234544 Pear|11 Pear|12 XBSJ|43949 XBSJ|43933 Result.txt: Apple|3123123|3434 Orange|99999999|1234544 Pear|11|12 XBSJ|43949|43933 This is what I had but it's not really doing what I needed. string[] combineconfig = File.ReadAllLines(@"C:\a.txt"); foreach (string ccline in combineconfig) { string[] readlines = File.ReadAllLines(@"C:\b.txt"); if (readlines.Contains(ccline)) { foreach (string rdlines in readlines) { string[] pslines = rdlines.Split('|'); File.AppendAllText(@"C:\result.txt", ccline + '|' + pslines[0]); } } I know realize it's not going to find the first "if" because it reads the entire line and cant find it. But i still believe my output file will not contain what I need.

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  • MPI Large Data all to all transfer

    - by csslayer
    My application of MPI has some process that generate some large data. Say we have N+1 process (one for master control, others are workers), each of worker processes generate large data, which is now simply write to normal file, named file1, file2, ..., fileN. The size of each file may be quite different. Now I need to send all fileM to rank M process to do the next job, So it's just like all to all data transfer. My problem is how should I use MPI API to send these files efficiently? I used to use windows share folder to transfer these before, but I think it's not a good idea. I have think about MPI_file and MPI_All_to_all, but these functions seems not to be so suitable for my case. Simple MPI_Send and MPI_Recv seems hard to be used because every process need to transfer large data, and I don't want to use distributed file system for now.

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