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  • Handling Corrupted JPEGs in C#

    - by ddango
    We have a process that pulls images from a remote server. Most of the time, we're good to go, the images are valid, we don't timeout, etc. However, every once and awhile we see this error similar to this: Unhandled Exception: System.Runtime.InteropServices.ExternalException: A generic error occurred in GDI+. at System.Drawing.Image.Save(Stream stream, ImageCodecInfo encoder, EncoderPa rameters encoderParams) at ConsoleApplication1.Program.Main(String[] args) in C:\images\ConsoleApplic ation1\ConsoleApplication1\Program.cs:line 24 After not being able to reproduce it locally, we looked closer at the image, and realized that there were artifacts, making us suspect corruption. Created an ugly little unit test with only the image in question, and was unable to reproduce the error on Windows 7 as was expected. But after running our unit test on Windows Server 2008, we see this error every time. Is there a way to specify non-strictness for jpegs when writing them? Some sort of check/fix we can use? Unit test snippet: var r = ReadFile("C:\\images\\ConsoleApplication1\\test.jpg"); using (var imgStream = new MemoryStream(r)) { using (var ms = new MemoryStream()) { var guid = Guid.NewGuid(); var fileName = "C:\\images\\ConsoleApplication1\\t" + guid + ".jpg"; Image.FromStream(imgStream).Save(ms, ImageFormat.Jpeg); using (FileStream fs = File.Create(fileName)) { fs.Write(ms.GetBuffer(), 0, ms.GetBuffer().Length); } } }

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  • Resize image on upload php

    - by blasteralfred
    Hi, I have a php script for image upload as below <?php $LibID = $_POST[name]; define ("MAX_SIZE","10000"); function getExtension($str) { $i = strrpos($str,"."); if (!$i) { return ""; } $l = strlen($str) - $i; $ext = substr($str,$i+1,$l); return $ext; } $errors=0; $image=$_FILES['image']['name']; if ($image) { $filename = stripslashes($_FILES['image']['name']); $extension = getExtension($filename); $extension = strtolower($extension); if (($extension != "jpg") && ($extension != "jpeg")) { echo '<h1>Unknown extension!</h1>'; $errors=1; exit(); } else { $size=filesize($_FILES['image']['tmp_name']); if ($size > MAX_SIZE*1024) { echo '<h1>You have exceeded the size limit!</h1>'; $errors=1; exit(); } $image_name=$LibID.'.'.$extension; $newname="uimages/".$image_name; $copied = copy($_FILES['image']['tmp_name'], $newname); if (!$copied) { echo '<h1>image upload unsuccessfull!</h1>'; $errors=1; exit(); }}} ?> which uploads the image file to a folder "uimages" in the root. I have made changes in the html file for the compact display of the image by defining "max-height" and "max-width". But i want to resize the image file on upload. The image file may have a maximum width of 100px and maximum height of 150px. The image proportions must be constrained. That is, the image may be smaller than the above dimensions, but, it should not exceed the limit. How can I make this possible?? Thanks in advance :) blasteralfred..

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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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  • 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 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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  • 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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  • OpenMP: Get total number of running threads

    - by Konrad Rudolph
    I need to know the total number of threads that my application has spawned via OpenMP. Unfortunately, the omp_get_num_threads() function does not work here since it only yields the number of threads in the current team. However, my code runs recursively (divide and conquer, basically) and I want to spawn new threads as long as there are still idle processors, but no more. Is there a way to get around the limitations of omp_get_num_threads and get the total number of running threads? If more detail is required, consider the following pseudo-code that models my workflow quite closely: function divide_and_conquer(Job job, int total_num_threads): if job.is_leaf(): # Recurrence base case. job.process() return left, right = job.divide() current_num_threads = omp_get_num_threads() if current_num_threads < total_num_threads: # (1) #pragma omp parallel num_threads(2) #pragma omp section divide_and_conquer(left, total_num_threads) #pragma omp section divide_and_conquer(right, total_num_threads) else: divide_and_conquer(left, total_num_threads) divide_and_conquer(right, total_num_threads) job = merge(left, right) If I call this code with a total_num_threads value of 4, the conditional annotated with (1) will always evaluate to true (because each thread team will contain at most two threads) and thus the code will always spawn two new threads, no matter how many threads are already running at a higher level. I am searching for a platform-independent way of determining the total number of threads that are currently running in my application.

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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • how to generate large image in compact framework

    - by Buthrakaur
    I need to generate large images (A4 image at 200 DPI, PNG format would be fine) in my compact framework application. This is impossible to do in standard way due to memory limitations (such big image will throw OOMException). Is there any library which offers file-backed stream image generation? Or I could generate many smaller stripes of images (each stripe representing a row of the large image) using standard Bitmap approach, but I need to merge them together afterwards - is there any method how to merge many smaller images into one large without having to instantiate large Bitmap instance (which would again cause OOM)?

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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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  • 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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  • Auto scale and rotate images

    - by Dave Jarvis
    Given: two images of the same subject matter; the images have the same resolution, colour depth, and file format; the images differ in size and rotation; and two lists of (x, y) co-ordinates that correlate the images. I would like to know: How do you transform the larger image so that it visually aligns to the second image? (Optional.) What are the minimum number of points needed to get an accurate transformation? (Optional.) How far apart do the points need to be to get an accurate transformation? The transformation would need to rotate, scale, and possibly shear the larger image. Essentially, I want to create (or find) a program that does the following: Input two images (e.g., TIFFs). Click several anchor points on the small image. Click the several corresponding anchor points on the large image. Transform the large image such that it maps to the small image by aligning the anchor points. This would help align pictures of the same stellar object. (For example, a hand-drawn picture from 1855 mapped to a photograph taken by Hubble in 2000.) Many thanks in advance for any algorithms (preferably Java or similar pseudo-code), ideas or links to related open-source software packages.

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