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  • Image rotate opecv error

    - by avd
    When I use this code to rotate the image, the destination image size remains same and hence the image gets clipped. Please provide me a way/code snippet to resize accordingly (like matlab does in imrotate) so that image does not get clipped and outlier pixels gets filled with all white instead of black. void imrotate(std::string imgPath,std::string angleStr,std::string outPath) { size_t found1,found2; found1=imgPath.find_last_of('/'); found2=imgPath.size()-4; IplImage* src=cvLoadImage(imgPath.c_str(), -1);; IplImage* dst; dst = cvCloneImage( src ); int angle = atoi(angleStr.c_str()); CvMat* rot_mat = cvCreateMat(2,3,CV_32FC1); CvPoint2D32f center = cvPoint2D32f( src->width/2, src->height/2 ); double scale = 1; cv2DRotationMatrix( center, angle, scale, rot_mat ); cvWarpAffine( src, dst, rot_mat); char angStr[4]; sprintf(angStr,"%d",angle); cvSaveImage(string(outPath+imgPath.substr(found1+1,found2-found1-1)+"_"+angStr+".jpg").c_str(),dst); cvReleaseImage(&src); cvReleaseImage(&dst); cvReleaseMat( &rot_mat ); } Original Image: Rotated Image:

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  • Filtering spectrum using FIR filters

    - by Alex Hoppus
    If i have signal values x[T] and filter coefficients b[i], i can perform filtering using convolution. Suppose i have spectrum of x (after FFT) and i need to perform filtering using filters coefficients, how can i perform this? I heard that in frequency domain it will be multiplying, rather than convolution (time domain). But i can't find an equation to use it. I have 614000 values in y = fft(x[T]) vector and 119 filter coefficients (generated using fdatool), i can't multiply them directly ... Thanks.

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  • Java Servlet framework that does things like rencoding images to preferred format etc.

    - by mP
    Are there any frameworks/libraries that provide servlets/filters etc that handle reencoding on the fly of images. interpret the accept headers and output the file, reencoding into the new format if necessary by checking the actual format of the original image file. provide a low and high quality version of an image. re encode an image into new dimensions. width and height parameters might query string parameters. I could create versions of the file in all the formats, at upload time but the seems overkill. I would rather lazily create the rencoded file and stick it in a cache if it gets served again etc.

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  • Parallel doseq for Clojure

    - by andrew cooke
    I haven't used multithreading in Clojure at all so am unsure where to start. I have a doseq whose body can run in parallel. What I'd like is for there always to be 3 threads running (leaving 1 core free) that evaluate the body in parallel until the range is exhausted. There's no shared state, nothing complicated - the equivalent of Python's multiprocessing would be just fine. So something like: (dopar 3 [i (range 100)] ; repeated 100 times in 3 parallel threads... ...) Where should I start looking? Is there a command for this? A standard package? A good reference? So far I have found pmap, and could use that (how do I restrict to 3 at a time? looks like it uses 32 at a time - no, source says 2 + number of processors), but it seems like this is a basic primitive that should already exist somewhere. clarification: I really would like to control the number of threads. I have processes that are long-running and use a fair amount of memory, so creating a large number and hoping things work out OK isn't a good approach (example which uses a significant chunk available mem). update: Starting to write a macro that does this, and I need a semaphore (or a mutex, or an atom i can wait on). Do semaphores exist in Clojure? Or should I use a ThreadPoolExecutor? It seems odd to have to pull so much in from Java - I thought parallel programming in Clojure was supposed to be easy... Maybe I am thinking about this completely the wrong way? Hmmm. Agents?

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  • How do I save an altered image in matlab?

    - by ef-i-blinky
    So I am using the code located here: http://wwwx.cs.unc.edu/~sjguy/CompVis/Features/BlobDetect.m and I was wondering how to save the final blob detected image. The image that I am doing the blob detection on gets shown and then he manually draws the lines on the image here: Xbar = cx1+X.*cos(alpha)+Y.*sin(alpha); Ybar = cy1+Y.*cos(alpha)-X.*sin(alpha); line(Xbar', Ybar', 'Color', color, 'LineWidth', ln_wid); I then want to save this image using something like imwrite. I have been reading around and it seems that no one really has an answer to to this problem. Thanks for any help you can give me, Josh

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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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  • .NET 4 ... Parallel.ForEach() question

    - by CirrusFlyer
    I understand that the new TPL (Task Parallel Library) has implemented the Parallel.ForEach() such that it works with "expressed parallelism." Meaning, it does not guarantee that your delegates will run in multiple threads, but rather it checks to see if the host platform has multiple cores, and if true, only then does it distribute the work across the cores (essentially 1 thread per core). If the host system does not have multiple cores (getting harder and harder to find such a computer) then it will run your code sequenceally like a "regular" foreach loop would. Pretty cool stuff, frankly. Normally I would do something like the following to place my long running operation on a background thread from the ThreadPool: ThreadPool.QueueUserWorkItem( new WaitCallback(targetMethod), new Object2PassIn() ); In a situation whereby the host computer only has a single core does the TPL's Parallel.ForEach() automatically place the invocation on a background thread? Or, should I manaully invoke any TPL calls from a background thead so that if I am executing from a single core computer at least that logic will be off of the GUI's dispatching thread? My concern is if I leave the TPL in charge of all this I want to ensure if it determines it's a single core box that it still marshalls the code that's inside of the Parallel.ForEach() loop on to a background thread like I would have done, so as to not block my GUI. Thanks for any thoughts or advice you may have ...

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  • Looking for a managed image parser library (JPEG, BMP, PNG, GIF)

    - by usr
    I am writing a discussion board software that will have "avatar" images for the users. I want to resize any picture that gets uploaded to a reasonable size. I could easily do that with System.Drawing but that is relying on GDI+ which has hat security problems before. The problem is that the images are untrusted. So I thought of using a fully managed lib to solve that problem because managed code cannot escape the sandbox (of course it can, but only if the code is user-supplied which it is not in my case). So does anybody know of a managed image parser library for JPEG, BMP, PNG and GIF? If some format is missing than I will have to live with that. Edit: Paint.NET also relies on GDI+. You might be interested in the discussion below, too.

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  • Image classification: recognizing various features of many buildings from images

    - by el chief
    so, let's say i have the long/lat or address of many buildings can get satellite images, "street view", and perhaps 3d/perspective views of buildings. want to find: height, number of floors, floor area (max building footprint) of the building. about 200k buildings. Is there a library for recognizing buildings from satellite shots or pictures? Kind of like face detection I suppose. Any other suggestions? Thanks!

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  • divide the image into 3*3 blocks

    - by Jayanth Silesh
    I have a matrix that does not happen to have dimensions that are multiples of 3 or it might. How can we divide the entire image into blocks of 3*3 matrices. (Can ignore the last ones which does not come under the 3*3 multiples. Also, the 3*3 matrices can be be saved in arrays. a=3; b=3; %window size x=size(f,1)/a; y=size(f,2)/b; %f is the original image m=a*ones(1,x); n=b*ones(1,y); I=mat2cell(f,m,n);

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  • How to replicate Google "Hangouts On Air" stream combining functionality?

    - by Rob Olmos
    I've been researching this one for quite a bit but haven't found any solid leads. I have a Wowza/Flash app with video chatroom functionality and would like to combine the streams server-side into one video/audio stream in order to be sent to a live Youtube channel. I've found a couple projects such as jMixer and some helpful keywords such as "vision mixer" to help with my search but looking for any previous experience or new ideas. The other option is building something like it myself with a commercial video decoding/encoding library to raw frames, stitching the frames together, then encoding it. I was originally going down this route but put project on hold. What are some ideas, keywords, or existing software (open source preferred) to take those live streams and combine them into one in real-time? Or is coding it myself the required route? Thanks!

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  • Implemeting "drawing modes" in a graphics library?

    - by banister
    i would like to implement 'drawing modes' (in my own graphics library). That is drawing with AND, OR, etc However i am storing colors using floats, each channel between 0 and 1.0 Do i have to first convert each color channel to 0-255 before i can use the AND, OR, etc drawing modes? and then convert back to float (0.0-1.0) ? Or is there another way of doing it? thanks

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  • read successive frames OpenCV using cvQueryframe

    - by AtharvaI
    Hi all I have a basic question in regards to cvQueryFrame() in OpenCV. I have the following code: IplImage *frame1,*frame2; frame1 = cvQueryFrame(capture); frame2 = cvQueryFrame(capture); Now my question is: if frame1 is a pointer to the first frame, is frame2 a pointer to the 2nd frame? So will the two cvQueryFrame() calls read successive frames? I thought I'd check myself first but the pointers frame1,frame2 seem to have the same hex value. :s I just need to capture two frames at a time and then need to process them. Thanks in advance

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  • How can I compress jpeg images in Java without losing any metadata in that image?

    - by guitarpoet
    I want compress jpeg files using Java. I do it like this: Read the image as BufferedImage Write the image to another file with compression rate. OK, that seems easy, but I find the ICC color profile and the EXIF information are gone in the new file and the DPI of the image is dropped from 240 to 72. It looks different from the origin image. I use a tool like preview in OS X. It can perfectly change the quality of the image without affecting other information. Can I done this in Java? At least keep the ICC color profile and let the image color look the same as the origin photo?

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  • 3x3 Average filter in matlab

    - by turingcomplete
    I've written code to smooth an image using a 3x3 averaging filter, however the output is strange, it is almost all black. Here's my code. function [filtered_img] = average_filter(noisy_img) [m,n] = size(noisy_img); filtered_img = zeros(m,n); for i = 1:m-2 for j = 1:n-2 sum = 0; for k = i:i+2 for l = j:j+2 sum = sum+noisy_img(k,l); end end filtered_img(i+1,j+1) = sum/9.0; end end end I call the function as follows: img=imread('img.bmp'); filtered = average_filter(img); imshow(uint8(filtered)); I can't see anything wrong in the code logic so far, I'd appreciate it if someone can spot the problem.

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  • Images won't load if they are of high size

    - by Fahim Parkar
    I have created web-application using JSF 2.0 and mysql. I am storing images in DB using MEDIUMBLOB. When I try to load image, I am able to see those images. However if the image size is big (1 MB or more), I can see half or 3/4th image on the browser. Any idea how to overcome this issue? Do I need to set any variable in JSF or MySQL? I know I should have saved the images over disk instead of DB, however this was client requirement. Client wanted to backup data and provide it to someone else and client don't want to backup DB and images also. Edit 1 Do I need to set any variables on mysql like query_cache. Edit 2 When I download same image and put below code it works perfectly. <h:graphicImage value="images/myImage4.png" width="50%" /> Edit 3 code is as below. <h:graphicImage value="DisplayImage?mainID=drawing" /> DisplayImage.java String imgLen = rs1.getString(1); int len = imgLen.length(); byte[] rb = new byte[len]; InputStream readImg = rs1.getBinaryStream(1); InputStream inputStream = readImg; int index = readImg.read(rb, 0, len); response.reset(); response.setHeader("Content-Length", String.valueOf(len)); response.setHeader("Content-disposition", "inline;filename=/file.png"); response.setContentType("image/png"); response.getOutputStream().write(rb, 0, len); response.getOutputStream().flush(); When I print len I get value as len=1548432

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  • live image edit , and crop

    - by 422
    I was just thinking, which is always dangerous. We use Valums Image uploader. Aside from that, I am looking for an inline image editor, but with a difference. User uploads an image ( lets say 800 x 600 ) Our system wants to see the image ( 170 x 32 ) now I know we can use php to resize images. But I was thinking, does anyone know of a system, where we can display the image, and user can scale, and crop image ( with say a predefined overlay ) By that they scale down to nearest acceptable size, and then click crop tool, which shows a div overlay with say 70% transparency that they can drag over the image, and then click crop. So image is cropped to exact size we need, then can save . I am sure I have seen some jquery stuff done like this, just cannot for life of me find it. Essentialy, we would like to offer a simple client side image processor, thats lightweight, and then the ability to save what they did . Sorry no code to show, as its more of a request. Regards

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  • Automatically download files in Ruby

    - by Obinna
    I'm trying to write a ruby script which automatically downloads some files from some server ever 30-45 minutes (to prevent overload) as long as my computer is turned on. It's possible that my computer might be turned off at some point, but the download should resume (probably re-download the current file). I already have the file list but I can't figure out how to make such a script to run autonomously. What are some ways I can do this?

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  • Detecting crosses in an image

    - by MrOrdinaire
    I am working on a program to detect the tips of a probing device and analyze the color change during probing. The input/output mechanisms are more or less in place. What I need now is the actual meat of the thing: detecting the tips. In the images below, the tips are at the center of the crosses. I thought of applying BFS to the images after some threshold'ing but was then stuck and didn't know how to proceed. I then turned to OpenCV after reading that it offers feature detection in images. However, I am overwhelmed by the vast amount of concepts and techniques utilized here and again, clueless about how to proceed. Am I looking at it the right way? Can you give me some pointers? Image extracted from short video Binary version with threshold set at 95

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  • Parallel computation of the median of a large array

    - by recipriversexclusion
    I got asked this question once and still haven't been able to figure it out: You have an array of N integers, where N is large, say, a billion. You want to calculate the median value of this array. Assume you have m+1 machines (m workers, one master) to distribute the job to. How would you go about doing this? Since the median is a nonlinear operator, you can't just find the median in each machine and then take the median of those values.

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  • Is it possible to add layers to .tiff images with .NET?

    - by Voyta
    Are there any .NET libraries etc. which allow adding layers (with text) to .tiff images? Something like annotations, so that it would be possible to separate them from image afterwards. I tried DotImage - it allows to add annotations, save them as embedded into image and load them afterwards, but no one other image viewer seems to recognize that they are there.

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