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  • WPF WriteableBitmap

    - by Sam
    I'm using WriteableBitmap on an image of type Bgra32 to change the pixel value of certain pixels. I'm setting the value to 0x77CCCCCC. After calling WritePixels, the pixels I set to 0x77CCCCCC show up with a value of 0x77FFFFFF. Why does this happen? How do I make the pixels have the correct value?

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  • Number of threads and thread numbers in Grand Central Dispatch

    - by raphgott
    I am using C and Grand Central Dispatch to parallelize some heavy computations. How can I get the number of threads used by GCD? Also is it possible to know on which thread a piece of code is currently running on? Basically I'd like to use sprng (parallel random numbers) with multiple streams and for that I need to know what stream id to use (and therefore what thread is being used).

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  • How to use Haar wavelet to detect LINES on an image?

    - by Ole Jak
    So I have Image like this I want to get something like this (I hevent drawn all lines I want but I hope you can get my idea) I want to use SURF ( (Speeded Up Robust Features) is a robust image descriptor, first presented by Herbert Bay et al. in 2006 ) or something that is based on sums of 2D Haar wavelet responses and makes an efficient use of integral images for finding all straight lines on image. I want to get relative to picture pixel coords start and end points of lines. So on this picture to find all lines between tiles and thouse 2 black lines on top. Is there any such Code Example (with lines search capability) to start from? I love C and C++ but any other readable code will probably work for me=)

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  • Training sets for AdaBoost algorithm

    - by palau1
    How do you find the negative and positive training data sets of Haar features for the AdaBoost algorithm? So say you have a certain type of blob that you want to locate in an image and there are several of them in your entire array - how do you go about training it? I'd appreciate a nontechnical explanation as much as possible. I'm new to this. Thanks.

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  • Run all SQL files in a directory

    - by Khalil Dahab
    I have a number of .sql files which I have to run in order to apply changes made by other developers on an SQL Server 2005 database. The files are named according to the following pattern: 0001 - abc.sql 0002 - abcef.sql 0003 - abc.sql ... Is there a way to run all of them in one go?

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  • Coordinate geometry operations in images/discrete space

    - by avd
    I have images which have line segments, rays etc. I am representing these line segments using Bresenham algorithm (means whatever coordinates I get using this algorithm between two points). Now I want to do operations such as finding intersection point between two line segments, finding the projection of one vector onto other etc... The problem is I am not working in continuous space. The line segments are being approximated using Bresenham algorithm. So I want suggestions on what are the best and most efficient ways to do this? A link to C++ library or implementation would also be good enough. Please suggest some books which deal with such problems.

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  • Matlab: Analysis of signal

    - by Mateusz
    Hi, I have a problem with this task: For free route perform frequency analysis and give parametrs of each signal component: time of beginning and ending of each component beginning and ending frequency amplitude (in time domain) in the beginning and end of each signal's component level of noise in dB Assume, that, the parametrs of each component like amplitude, frequency is changing lineary in time. Frequency of sampling is 1000Hz For example I have signal like this: Nx=64; fs=1000; t=1/fs*(0:Nx-1); %========================== A1=1; A2=4; f1=500; f2=1000; x1=A1*cos(2*pi*f1*t); x2=A2*sin(2*pi*f2*t); %========================== x=x1+x2;

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  • How to generate a lower frequency version of a signal in Matlab?

    - by estourodepilha.com
    With a sine input, I tried to modify it's frequency cutting some lower frequencies in the spectrum, shifting the main frequency towards zero. As the signal is not fftshifted I tried to do that by eliminating some samples at the begin and at the end of the fft vector: interval = 1; samplingFrequency = 44100; signalFrequency = 440; sampleDuration = 1 / samplingFrequency; timespan = 1 : sampleDuration : (1 + interval); original = sin(2 * pi * signalFrequency * timespan); fourierTransform = fft(original); frequencyCut = 10; %% Hertz frequencyCut = floor(frequencyCut * (length(pattern) / samplingFrequency) / 4); %% Samples maxFrequency = length(fourierTransform) - (2 * frequencyCut); signal = ifft(fourierTransform(frequencyCut + 1:maxFrequency), 'symmetric'); But it didn't work as expected. I also tried to remove the center part of the spectrum, but it wielded a higher frequency sine wave too. How to make it right?

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  • Can anyone give me a sample DSP script in C/C++

    - by Andrew
    Im working on a (Audio) DSP project and just wondering if there are any sample (Open source) DSP example that are written in c or c++, for my MSP430 Chip. I just want something as a guideline so i can program my own script using the ACD and DCA on my board for sampling. http://focus.ti.com/docs/toolsw/folders/print/msp-exp430f5438.html Thats my board, MSP430F5438 Experimenter Board, from what i herd it can run dsp script via the USB connection with the computer. Im using CCS ( From TI, code composer studio) and Octave/Matlab. Just any DSP example scripts or sites that will help me create my own would be appreciated. What im tying to do, Partial audio (sampled) track -- Nyquist rate sampling -- over- and undersampling -- reconstruction of the audio track.

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  • Video match anlysis

    - by Mohammad
    Hi every body I am looking forward to find an algorithm to detect a pattern in a given video file. Actually I am going to index moments in a tennis match video at which service (first kick after a goal) is shot. PS1: sorry for broken English. PS2: I DO NOT know anything about tennis except that you need a ball to play!!

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  • Will the values of label and its correspondences change if Image is rotated?

    - by Vinayak Agarwal
    Hi all I have an image in which a text like "VINAYAK 123" is written. The text in the image is at a certain angle, say 30degrees. Now when I extract the labels of the connected components, I get V-1, I-2, N-3, A-4,Y-5,A-6,K-7, 1-8,2-9,3-10( Format: Character- Label No.). Now I rotate the image 30 degrees in the clockwise direction to make the text in the image horizontal. My question is that now if I extract the labels of the connected components, will the character and the label no. correspondence still remain the same? Thanks in advance!

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  • iPhone OS: Strategies for high density image work

    - by Jasconius
    I have a project that is coming around the bend this summer that is going to involve, potentially, an extremely high volume of image data for display. We are talking hundreds of 640x480-ish images in a given application session (scaled to a smaller resolution when displayed), and handfuls of very large (1280x1024 or higher) images at a time. I've already done some preliminary work and I've found that the typical 640x480ish image is just a shade under 1MB in memory when placed into a UIImageView and displayed... but the very large images can be a whopping 5+ MB's in some cases. This project is actually be targeted at the iPad, which, in my Instruments tests seems to cap out at about 80-100MB's of addressable physical memory. Details aside, I need to start thinking of how to move huge volumes of image data between virtual and physical memory while preserving the fluidity and responsiveness of the application, which will be high visibility. I'm probably on the higher ends of intermediate at Objective-C... so I am looking for some solid articles and advice on the following: 1) Responsible management of UIImage and UIImageView in the name of conserving physical RAM 2) Merits of using CGImage over UIImage, particularly for the huge images, and if there will be any performance gain 3) Anything dealing with memory paging particularly as it pertains to images I will epilogue by saying that the numbers I have above maybe off by about 10 or 15%. Images may or may not end up being bundled into the actual app itself as opposed to being loaded in from an external server.

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  • Solid FFmpeg wrapper for C#/.NET

    - by Lillemanden
    I have been searching the web for some time for a solid FFmpeg wrapper for C#/.NET. But I have yet to come up with something useful. I have found the following three projects, but all of them apears to be dead in early alpha stage. FFmpeg.NET ffmpeg-sharp FFLIB.NET So my question is if anyone knows of a wrapper project that is more mature? I am not looking for a full transcoding engine with job queues and more. Just a simple wrapper so I do not have to make a command line call and then parse the console output, but can make method calls and use eventlisteners for progress. And please feel free to mention any active projects, even if they are stil in the early stages.

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  • Parallelism in Python

    - by fmark
    What are the options for achieving parallelism in Python? I want to perform a bunch of CPU bound calculations over some very large rasters, and would like to parallelise them. Coming from a C background, I am familiar with three approaches to parallelism: Message passing processes, possibly distributed across a cluster, e.g. MPI. Explicit shared memory parallelism, either using pthreads or fork(), pipe(), et. al Implicit shared memory parallelism, using OpenMP. Deciding on an approach to use is an exercise in trade-offs. In Python, what approaches are available and what are their characteristics? Is there a clusterable MPI clone? What are the preferred ways of achieving shared memory parallelism? I have heard reference to problems with the GIL, as well as references to tasklets. In short, what do I need to know about the different parallelization strategies in Python before choosing between them?

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  • php gdlib angle problem

    - by creativz
    I'm using php gd lib 5.2.13 and tried to make a picture with imagettftext ($image, $color and $font are defined of course). imagettftext($image, 12, 90, 10, 20, $black, $font, "This.is_a test 123"); //image, font size, angle, x value, y value, color, font, text As you can see I want the angle to be 90°. The problem is that the text is not beeing rotated properly, e.g. the dots are at the top (and not at the bottom) of the text. I read that this is a common issue and has been fixed in php gdlib 5.3, But since I have 5.2.13 running on a webhost (...) is there a solution to rotate it properly with using gdlib 5.2.13? Thanks!

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  • Generating a scalogram of a signal

    - by Goz
    Hi there, I'm trying to build a scalogram view for my app to see whether there is relevant information we can retrieve from a wavelet transform as opposed to using a spectograms to see what can be retrieved via an FFT. So far I can take a wave form and I can perform the forward wavelet transform on it. However I am lost at the next step. How do I turn this information into power/energy information? I have a set of wave forms at different frequencies but I have, as I say, no frequency information. Can anyone tell me what the next step is for turning this transformed data into a scalogram? Any help would be much appreciated because my google skills are failing me!

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  • How do you composite an image onto another image with PIL in Python?

    - by Sebastian
    I need to take an image and place it onto a new, generated white background in order for it to be converted into a downloadable desktop wallpaper. So the process would go: 1) Generate new, all white image with 1440x900 dimensions 2) Place existing image on top, centered 3) Save as single image In PIL, I see the ImageDraw object, but nothing indicates it can draw existing image data onto another image. Suggestions or links anyone can recommend?

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  • Correct way to Convert 16bit PCM Wave data to float

    - by fredley
    I have a wave file in 16bit PCM form. I've got the raw data in a byte[] and a method for extracting samples, and I need them in float format, i.e. a float[] to do a Fourier Transform. Here's my code, does this look right? I'm working on Android so javax.sound.sampled etc. is not available. private static short getSample(byte[] buffer, int position) { return (short) (((buffer[position + 1] & 0xff) << 8) | (buffer[position] & 0xff)); } ... float[] samples = new float[samplesLength]; for (int i = 0;i<input.length/2;i+=2){ samples[i/2] = (float)getSample(input,i) / (float)Short.MAX_VALUE; }

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  • How to display part of an image for the specific width and height?

    - by Brady Chu
    Recently I participated in a web project which has a huge large of images to handle and display on web page, we know that the width and height of images end users uploaded cannot be control easily and then they are hard to display. At first, I attempted to zoom in/out the images to rearch an appropriate presentation, and I made it, but my boss is still not satisfied with my solution, the following is my way: var autoResizeImage = function(maxWidth, maxHeight, objImg) { var img = new Image(); img.src = objImg.src; img.onload = function() { var hRatio; var wRatio; var Ratio = 1; var w = img.width; var h = img.height; wRatio = maxWidth / w; hRatio = maxHeight / h; if (maxWidth == 0 && maxHeight == 0) { Ratio = 1; } else if (maxWidth == 0) { if (hRatio < 1) { Ratio = hRatio; } } else if (maxHeight == 0) { if (wRatio < 1) { Ratio = wRatio; } } else if (wRatio < 1 || hRatio < 1) { Ratio = (wRatio <= hRatio ? wRatio : hRatio); } if (Ratio < 1) { w = w * Ratio; h = h * Ratio; } w = w <= 0 ? 250 : w; h = h <= 0 ? 370 : h; objImg.height = h; objImg.width = w; }; }; This way is only intended to limit the max width and height for the image so that every image in album still has different width and height which are still very urgly. And right at this minute, I know we can create a DIV and use the image as its background image, this way is too complicated and not direct I don't want to take. So I's wondering whether there is a better way to display images with the fixed width and height without presentation distortion? Thanks.

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