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• Matlab - Propagate unit vectors on to the edge of shape boundaries

  - by Graham

  Hi I have a set of unit vectors which I want to propagate on to the edge of shape boundary defined by a binary image. The shape boundary is defined by a 1px wide white edge. I also have the coordinates of these points stored in a 2 row by n column matrix. The shape forms a concave boundary with no holes within itself made of around 2500 points. What would be the best method to do this? Are there some sort of ray tracing algorithms that could be used? Or would it be a case of taking the unit vector and multiplying it by a scalar and testing after multiplication if the end point of the vector is outside the shape boundary. When the end point of the unit vector is outside the shape, just find the point of intersection? Thank you very much in advance for any help!

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• In parallel.for share value more then one.

  - by user347918

  Here is problem. long sum = 0; Parallel.For(1, 10000, y => { sum1 += y;} ); Solution is .. Parallel.For<int>(0, result.Count, () => 0, (i, loop, subtotal) => { subtotal += result[i]; return subtotal; }, (x) => Interlocked.Add(ref sum, x) ); if there are two parameters in this code. For example long sum1 = 0; long sum2 = 0; Parallel.For(1, 10000, y => { sum1 += y; sum2=sum1*y; } ); what will we do ? i am guessing that have to use array ! int[] s=new int[2]; Parallel.For<int[]>(0, result.Count, () => s, (i, loop, subtotal) => { subtotal[0] += result[i]; subtotal[1] -= result[i]; return subtotal; }, (x) => Interlocked.Add(ref sum1, x[0]) //but how about sum1 i tried several way but it doesn't work. //for example like that //(x[0])=> Interlocked.Add (ref sum1, x[0]) //(x[1])=> Interlocked.Add (ref sum2, x[1]));

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• Thumbnail image saved with worse quality on Windows Server 2003

  - by Angelo

  Hello, In asp.net 2.0 application I am trying to create thumbnails from uploaded images. However when I test the application on my PC under Windows7 it works fine, but on the real Windows 2003 Server the resized image has worse quality. Where this difference could come from? Different JPEG codec or what, if Yes how it can be updated on Win 2003 Server? Thanks! Here is the code: Resize of the Image: Bitmap newBmp = new Bitmap(imgWidth, imgHeight, PixelFormat.Format24bppRgb); newBmp.SetResolution(inputBmp.HorizontalResolution, inputBmp.VerticalResolution); //Create a graphics object attached to the new bitmap Graphics newBmpGraphics = Graphics.FromImage(newBmp); newBmpGraphics.InterpolationMode = InterpolationMode.HighQualityBicubic; newBmpGraphics.SmoothingMode = SmoothingMode.HighQuality; newBmpGraphics.PixelOffsetMode = PixelOffsetMode.HighQuality; newBmpGraphics.DrawImage(inputBmp, new Rectangle(0, 0, imgWidth, imgHeight), new Rectangle(0, 0, inputBmp.Width, inputBmp.Height), GraphicsUnit.Pixel); Save of the Image: System.IO.Stream imgStream = new System.IO.MemoryStream(); //Get the ImageCodecInfo for the desired target format ImageCodecInfo destCodec = FindCodecForType(ImageMimeTypes.JPEG); if (destCodec == null) { //No codec available for that format throw new ArgumentException("The requested format image/jpeg does not have an available codec installed", "destFormat"); } //Create an EncoderParameters collection to contain the //parameters that control the dest format's encoder EncoderParameters destEncParams = new EncoderParameters(1); EncoderParameter qualityParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality,(long)quality); destEncParams.Param[0] = qualityParam; //Save w/ the selected codec and encoder parameters inputBmp.Save(imgStream, destCodec, destEncParams); Bitmap destBitmap = new Bitmap(imgStream);

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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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• Which library should I use for server-side image manipulation on Node.JS?

  - by Andrew

  I found a quite large list of available libraries on Node.JS wiki but I'm not sure which of those are more mature and provide better performance. Basically I want to do the following: load some images to a server from external sources put them onto one big canvas crop and mask them a bit apply a filter or two Resize the final image and give a link to it Big plus if the node package works on both Linux and Windows.

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• Bash: any command to replace strings in text files?

  - by mikez302

  I have a hierarchy of directories containing many text files. I would like to search for a particular text string every time it comes up in one of the files, and replace it with another string. For example, I may want to replace every occurrence of the string "Coke" with "Pepsi". Does anyone know how to do this? I am wondering if there is some sort of Bash command that can do this without having to load all these files in an editor, or come up with a more complex script to do it. I found this page explaining a trick using sed, but it doesn't seem to work in files in subdirectories.

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• Converting an image in 8-bit grayscale RAW image in java

  - by deejay08

  Please let me know how to convert a JPG/PNG/BMP image into a 8-bit grayscale RAW image in Java. Is it possible to obtain using ImageIO API?

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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 unblend two images from a blend image

  - by gavishna

  I have blended/merged 2 images img1 and img2 with this code which is woking fine.What i want to know is how to obtain the original two images img1 and img2.The code for blending is as under img1=imread('C:\MATLAB7\Picture5.jpg'); img2=imread('C:\MATLAB7\Picture6.jpg'); for i=1:size(img1,1) for j=1:size(img1,2) for k=1:size(img1,3) output(i,j,k)=(img1(i,j,k)+img2(i,j,k))/2; end end end imshow(output,[0 255]);

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• Executing functions parallelly in PHP

  - by binaryLV

  Hi! Can PHP call a function and don't wait for it to return? So something like this: function callback($pause, $arg) { sleep($pause); echo $arg, "\n"; } header('Content-Type: text/plain'); fast_call_user_func_array('callback', array(3, 'three')); fast_call_user_func_array('callback', array(2, 'two')); fast_call_user_func_array('callback', array(1, 'one')); would output one (after 1 second) two (after 2 seconds) three (after 3 seconds) rather than three (after 3 seconds) two (after 3 + 2 = 5 seconds) one (after 3 + 2 + 1 = 6 seconds) Main script is intended to be run as a permanent process (TCP server). callback() function would receive data from client, execute external PHP script and then do something based on other arguments that are passed to callback(). The problem is that main script must not wait for external PHP script to finish. Result of external script is important, so exec('php -f file.php &') is not an option.

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• using Hibernate to loading 20K products, modifying the entity and updating to db

  - by Blankman

  I am using hibernate to update 20K products in my database. As of now I am pulling in the 20K products, looping through them and modifying some properties and then updating the database. so: load products foreach products session begintransaction productDao.MakePersistant(p); session commit(); As of now things are pretty slow compared to your standard jdbc, what can I do to speed things up? I am sure I am doing something wrong here.

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• Automatic people counting + twittering.

  - by c2h2

  Want to develop a system accurately counting people that go through a normal 1-2m wide door. and twitter whenever people goes in or out and tells how many people remain inside. Now, Twitter part is easy, but people counting is difficult. There is some semi existing counting solution, but they do not quite fit my needs. My idea/algorithm: Should I get some infra-red camera mounting on top of my door and constantly monitoring, and divide the camera image into several grid and calculating they entering and gone? can you give me some suggestion and starting point?

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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++: FFMPEG and SDL resources

  - by advs89

  I'm looking for resources (preferably books, but websites are fine too) for using FFMPEG and/or SDL with C++. Stuff I'd like to be able to do (eventually): Decode and play videos in realtime to a QT widget (the QT part isn't a problem) Overlay text and images on the video (in realtime) Loop video Cross-fade from one video to another (in realtime) Some kind of DVD functionality LIVE sources? (i.e. webcam, stream, etc.) So far I've looked at (and consider helpful) the following resources: FFMPEG and SDL Tutorial by Dranger (extremely helpful) StackOverflow: ffmpeg C API documentation/tutorial (not a duplicate, btw) Sample code bundled with FFMPEG libraries (I'll try and update this list with anything helpful below) Thanks for any help... Also: Operating System is Windows (but maybe one day cross-platform) Also 2: Resources using alternatives are welcome too... i.e. DirectShow, VFW, etc.

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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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• character matching in grayscale image

  - by maximus

  I made patterns: images with the "A" letter of different sizes (from 12 to 72: 12, 14, .., 72) And I tested the method of pattern matching and it gave a good results. One way to select text regions from image is to run that algorithm for all small and big letters and digits of different sizes. And fonts! I don't like it. Instead of it I want to make something like a universal pattern or better to say: scanning image with different window sizes and select those regions where some function (probability of that there is a character at that window) is more than some fixed value. Do you know any methods or ideas to make that function? It must work with original image (grayscale).

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• haar transformation on an image

  - by kabatusuka

  hello, i need some help with haar transformation, i have to apply it on an image. My math is bad, my english not all that awesome and i find it hard to understand from articles on the internet. I found this page http://www.cs.ucf.edu/~mali/haar/haar.cpp where the haar transformation is applied on 2d matrix. I suppose if i give image pixels matrix in there, it should work? im confused about this stuff, could someone enlighten me a bit please? Thank you!

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• How do I prevent ImageMagick convert from scaling images *up*?

  - by Kyle

  I'm using ImageMagick's convert tool to generate image thumbnails for a web application. I'm using notation like so: 600x600> The images are indeed scaled to 600px wide/tall (depending on the longer side) and proportions are properly maintained, however images less than 600px in either direction are scaled up — this behavior is not desired. Is there a way to prevent convert from scaling images up if the destination dimensions both exceed the original image size?

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• What hash algorithms are parallelizable? Optimizing the hashing of large files utilizing on multi-co

  - by DanO

  I'm interested in optimizing the hashing of some large files (optimizing wall clock time). The I/O has been optimized well enough already and the I/O device (local SSD) is only tapped at about 25% of capacity, while one of the CPU cores is completely maxed-out. I have more cores available, and in the future will likely have even more cores. So far I've only been able to tap into more cores if I happen to need multiple hashes of the same file, say an MD5 AND a SHA256 at the same time. I can use the same I/O stream to feed two or more hash algorithms, and I get the faster algorithms done for free (as far as wall clock time). As I understand most hash algorithms, each new bit changes the entire result, and it is inherently challenging/impossible to do in parallel. Are any of the mainstream hash algorithms parallelizable? Are there any non-mainstream hashes that are parallelizable (and that have at least a sample implementation available)? As future CPUs will trend toward more cores and a leveling off in clock speed, is there any way to improve the performance of file hashing? (other than liquid nitrogen cooled overclocking?) or is it inherently non-parallelizable?

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• efficient video format/codec for sparse & binary blob tracking

  - by user391339

  I am working on a blob tracking project and have many high-definition videos that I would like to reduce in size for storage and downstream tracking/shape-analysis. I want to use a lossless method that takes advantage of the black and white nature of the video as well as the fact that not much is moving between individual frames. The videos are quite sparse, with 5 to 10 b&w blobs per frame occupying <30% of the space in total, with each blob moving <5-10% of the field of view between frames and not changing shape too much between 2-3 frames. I will work in Python, Matlab, or LabView for this project, and could use a batch utility if available. It may be worthwhile to export the files as compressed image stacks if a proper video format can't be found. What are the pros and cons of this? A video codec uses correlations between neighboring frames, so it should be more efficient, but not if the wrong one is chosen or if it is improperly configured.

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• Concurrent Threads in C# using BackgroundWorker

  - by Jim Fell

  My C# application is such that a background worker is being used to wait for the acknowledgement of some transmitted data. Here is some psuedo code demonstrating what I'm trying to do: UI_thread { TransmitData() { // load data for tx // fire off TX background worker } RxSerialData() { // if received data is ack, set ack received flag } } TX_thread { // transmit data // set ack wait timeout // fire off ACK background worker // wait for ACK background worker to complete // evaluate status of ACK background worker as completed, failed, etc. } ACK_thread { // wait for ack received flag to be set } What happens is that the ACK BackgroundWorker times out, and the acknowledgement is never received. I'm fairly certain that it is being transmitted by the remote device because that device has not changed at all, and the C# application is transmitting. I have changed the ack thread from this (when it was working)... for( i = 0; (i < waitTimeoutVar) && (!bAckRxd); i++ ) { System.Threading.Thread.Sleep(1); } ...to this... DateTime dtThen = DateTime.Now(); DateTime dtNow; TimeSpan stTime; do { dtNow = DateTime.Now(); stTime = dtNow - dtThen; } while ( (stTime.TotalMilliseconds < waitTimeoutVar) && (!bAckRxd) ); The latter generates a very acurate wait time, as compared to the former. However, I am wondering if removal of the Sleep function is interferring with the ability to receive serial data. Does C# only allow one thread to run at a time, that is, do I have to put threads to sleep at some time to allow other threads to run? Any thoughts or suggestions you may have would be appreciated. I am using Microsoft Visual C# 2008 Express Edition. Thanks.

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• Display a loading message / gif

  - by Pankaj

  I am facing a problem on load pdf on browser. its working fine but slow in load. That's why i want to display a loading message / gif until it's fully loaded so the user isn't looking at a blank screen. My question is same as previous question http://stackoverflow.com/questions/1138232/html-embedded-pdfs-onload

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• Python: How to extract xml embedded in a html file?

  - by georgehu

  I have a html file with xml snipped embedded, the source code is pasted in the pastbin: http://pastebin.com/Hy0QaWk8 my task is to extract the text enclosed in the first textarea, which is a xml snippet, from the html. Without any change to the original snippet. I'm able to get it by using the BeautifulSoup, but it changes all the tag names into lower case.

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• Android - capture video with watermark

  - by androdevo

  Hello, I know how to capture video on android device, but i would like to capture video and add some other information on it e.g. some funny timeclock and save it all to file so the person watching the video will see the exact time of capturing. I would also like to add some watermark. Do you know how can i do it or is it possible on android device? I read the API but couldnt find anything that could help me.

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• What scripting language would you use to put text over a generated image ?

  - by Younes

  I got this question from my cousin: "What will be the best way to create a similar working website just like: http://www.plakletters.nl". I have looked into the website and think that to start of with i'm gonna help my cousin write a script that loads all fonts installed on the system into a dropdownlist. This dropdownlist will post a font value back to the page and will create images with the input of a user that comes from a textbox. This images will have to be created server side, and I also want to give the users the ability (in the future) to lay their own text over an uploaded image, to see what the result will look like on their own image. I found some information about how to create images using php, I don't know if php can output a list of installed fonts from the system it's running on. What scripting language would you use to get this job done? Keep in mind i would just like to start with outputting some images based on user input using a scripting language.

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