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  • How are you taking advantage of Multicore?

    - by tgamblin
    As someone in the world of HPC who came from the world of enterprise web development, I'm always curious to see how developers back in the "real world" are taking advantage of parallel computing. This is much more relevant now that all chips are going multicore, and it'll be even more relevant when there are thousands of cores on a chip instead of just a few. My questions are: How does this affect your software roadmap? I'm particularly interested in real stories about how multicore is affecting different software domains, so specify what kind of development you do in your answer (e.g. server side, client-side apps, scientific computing, etc). What are you doing with your existing code to take advantage of multicore machines, and what challenges have you faced? Are you using OpenMP, Erlang, Haskell, CUDA, TBB, UPC or something else? What do you plan to do as concurrency levels continue to increase, and how will you deal with hundreds or thousands of cores? If your domain doesn't easily benefit from parallel computation, then explaining why is interesting, too. Finally, I've framed this as a multicore question, but feel free to talk about other types of parallel computing. If you're porting part of your app to use MapReduce, or if MPI on large clusters is the paradigm for you, then definitely mention that, too. Update: If you do answer #5, mention whether you think things will change if there get to be more cores (100, 1000, etc) than you can feed with available memory bandwidth (seeing as how bandwidth is getting smaller and smaller per core). Can you still use the remaining cores for your application?

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  • Calculating length of objects in binary image - algorithm

    - by Jacek
    I need to calculate length of the object in a binary image (maximum distance between the pixels inside the object). As it is a binary image, so we might consider it a 2D array with values 0 (white) and 1 (black). The thing I need is a clever (and preferably simple) algorithm to perform this operation. Keep in mind there are many objects in the image. The image to clarify: Sample input image:

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  • selecting the pixels from an image in opencv

    - by ajith
    hi everyone, this is refined version of my previous question http://stackoverflow.com/questions/2602628/computing-matting-laplacian-matrix-of-an-image actually i want to do following operation... summation for all k|(i,j)?wk [(Ii-µk)*(Ij-µk)]...where wk is 3X3 window & µk is mean of wk...here i dont know how to select Ii & Ij separately from an image which is 2 dimensional[Iij]...or does the eqn means anything else??please someone help me..

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  • How to overwirte i-frames of a video?

    - by Dominik
    hi, i want to destroy alle i-frames of a video. doing this i want to check if encrypting only the i-frames of a video would be sufficient for making it unwatchable. How can i do this? Only removing them and recompressing the video would not be the same as really overwriting the iframe in the stream without recalculating b-frames etc.

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  • Is using the .NET Image Conversion enough?

    - by contactmatt
    I've seen a lot of people try to code their own image conversion techniques. It often seems to be very complicated, and ends up using GDI+ function calls, and manipulating bits of the image. This has got me wondering if I am missing something in the simplicity of .NET's image conversion call when saving an image. Here's the code I have: Bitmap tempBmp = new Bitmap("c:\temp\img.jpg"); Bitmap bmp = new Bitmap(tempBmp, 800, 600); bmp.Save(c:\temp\img.bmp, //extension depends on format ImageFormat.Bmp) //These are all the ImageFormats I allow conversion to within the program. Ignore the syntax for a second ;) ImageFormat.Gif) //or ImageFormat.Jpeg) //or ImageFormat.Png) //or ImageFormat.Tiff) //or ImageFormat.Wmf) //or ImageFormat.Bmp)//or ); This is all I'm doing in my image conversion. Just setting the location of where the image should be saved, and passing it an ImageFormat type. I've tested it the best I can, but I'm wondering if I am missing anything in this simple format conversion, or if this is sufficient?

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  • Simplex noise vs Perlin noise

    - by raRaRa
    I would like to know why Perlin noise is still so popular today after Simplex came out. Simplex noise was made by Ken Perlin himself and it was suppose to take over his old algorithm which was slow for higher dimensions and with better quality (no visible artifacts). Simplex noise came out in 2001 and over those 10 years I've only seen people talk of Perlin noise when it comes to generating heightmaps for terrains, creating procedural textures, et cetera. Could anyone help me out, is there some downside of Simplex noise? I heard rumors that Perlin noise is faster when it comes to 1D and 2D noise, but I don't know if it's true or not. Thanks!

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  • Loading .png image from array of uint8_t into OpenGL ES texture

    - by unknownthreat
    Normally, when we want to load a texture for OpenGL ES with .png, we simply add the .png images into XCode. The .png files will be altered for optimization by XCode and these altered png files can loaded into OpenGL ES texture during the runtime. However, what I am trying to do is quite different. I am trying to load a .png file that is not from the prebuilt/compile. The png file will be transmitted externally from UDP, and it will be in the form of array of bytes. I am very sure that the png is transferred correctly, but when it comes to displaying the png image in the form of the OpenGL ES texture, the image somehow shows incorrectly. The colors that are being sent are presented but the positions are somehow very incorrect. However, the position of the colors still retain some aspects of the original position. Here: The left image shows the original .png, while the right shows the png being displayed on iPhone using OpenGL ES Texture. It looks more like the png data is not being decoded or incorrectly processed. Below is OpenGL ES code for turning the image into texture: - (void) setTextureFromImageByte: (uint8_t*)imageByte{ if (self = [super init]){ NSData* imageData = [[NSData alloc] initWithBytes: imageByte length: imageLength]; UIImage* img = [[UIImage alloc] initWithData: imageData]; CGImageRef image = img.CGImage; int width = 512; int height = 512; if (image){ int tempWidth = (int)width, tempHeight = (int)height; if ((tempWidth & (tempWidth - 1)) != 0 ){ NSLog(@"CAUTION! width is not power of 2. width == %d", tempWidth); }else if ((tempHeight & (tempHeight - 1)) != 0 ){ NSLog(@"CAUTION! height is not power of 2. height == %d", tempHeight); }else{ void *spriteData = calloc(width * 4, height * 4); CGContextRef spriteContext = CGBitmapContextCreate(spriteData, width, height, 8, width*4, CGImageGetColorSpace(image), kCGImageAlphaPremultipliedLast); CGContextDrawImage(spriteContext, CGRectMake(0.0, 0.0, width, height), image); CGContextRelease(spriteContext); glBindTexture(GL_TEXTURE_2D, 1); glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 320, 435, GL_RGBA, GL_UNSIGNED_BYTE, spriteData); free(spriteData); } }else NSLog(@"ERROR: Image not loaded..."); [img release]; [imageData release]; } } So does anyone knows how to deal with this? Is it because of iPhone only accepts altered png from XCode? What can we do in this case in order to make the png image be able to display correctly?

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  • convert RGB values to equivalent HSV values using python

    - by sree01
    Hi, I want to convert RGB values to HSV using python. I got some code samples, which gave the result with the S and V values greater than 100. (example : http://code.activestate.com/recipes/576554-covert-color-space-from-hsv-to-rgb-and-rgb-to-hsv/ ) . anybody got a better code which convert RGB to HSV and vice versa thanks

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  • Need help using libpng to read an image

    - by jonathanasdf
    Here is my function... I don't know why it's not working. The resulting image looks nothing like what the .png looks like. But there's no errors either. bool Bullet::read_png(std::string file_name, int pos) { png_structp png_ptr; png_infop info_ptr; FILE *fp; if ((fp = fopen(file_name.c_str(), "rb")) == NULL) { return false; } png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL); if (png_ptr == NULL) { fclose(fp); return false; } info_ptr = png_create_info_struct(png_ptr); if (info_ptr == NULL) { fclose(fp); png_destroy_read_struct(&png_ptr, NULL, NULL); return false; } if (setjmp(png_jmpbuf(png_ptr))) { png_destroy_read_struct(&png_ptr, &info_ptr, NULL); fclose(fp); return false; } png_init_io(png_ptr, fp); png_read_png(png_ptr, info_ptr, PNG_TRANSFORM_STRIP_16 | PNG_TRANSFORM_SWAP_ALPHA | PNG_TRANSFORM_EXPAND, NULL); png_uint_32 width = png_get_image_width(png_ptr, info_ptr); png_uint_32 height = png_get_image_height(png_ptr, info_ptr); imageData[pos].width = width; imageData[pos].height = height; png_bytepp row_pointers; row_pointers = png_get_rows(png_ptr, info_ptr); imageData[pos].data = new unsigned int[width*height]; for (unsigned int i=0; i < height; ++i) { memcpy(&imageData[pos].data[i*width], &row_pointers[i], width*sizeof(unsigned int)); } png_destroy_read_struct(&png_ptr, &info_ptr, NULL); fclose(fp); for (unsigned int i=0; i < height; ++i) { for (unsigned int j=0; j < width; ++j) { unsigned int val = imageData[pos].data[i*width+j]; if (val != 0) { unsigned int a = ((val >> 24)); unsigned int r = (((val - (a << 24)) >> 16)); unsigned int g = (((val - (a << 24) - (r << 16)) >> 8)); unsigned int b = (((val - (a << 24) - (r << 16) - (g << 8)))); // for debugging std::string s(AS3_StringValue(AS3_Int(i*width+j))); s += " "; s += AS3_StringValue(AS3_Int(val)); s += " "; s += AS3_StringValue(AS3_Int(a)); s += " "; s += AS3_StringValue(AS3_Int(r)); s += " "; s += AS3_StringValue(AS3_Int(g)); s += " "; s += AS3_StringValue(AS3_Int(b)); AS3_Trace(AS3_String(s.c_str())); } } } return true; } ImageData is just a simple struct to keep x, y, width, and height, and imageData is an array of that struct. struct ImageData { int x; int y; int width; int height; unsigned int* data; }; Here is a side by side screenshot of the input and output graphics (something I made in a minute for testing), and this was after setting alpha to 255 in order to make it show up (because the alpha I was getting back was 1). Left side is original, right side is what happened after reading it through this function. Scaled up 400% for visibility. Here is a log of the traces: 0 16855328 1 1 49 32 1 16855424 1 1 49 128 2 16855456 1 1 49 160 3 16855488 1 1 49 192 4 16855520 1 1 49 224 5 16855552 1 1 50 0 6 16855584 1 1 50 32 7 16855616 1 1 50 64 8 16855424 1 1 49 128 9 16855456 1 1 49 160 10 16855488 1 1 49 192 11 16855520 1 1 49 224 12 16855552 1 1 50 0 13 16855584 1 1 50 32 14 16855616 1 1 50 64 15 16855648 1 1 50 96 16 16855456 1 1 49 160 17 16855488 1 1 49 192 18 16855520 1 1 49 224 19 16855552 1 1 50 0 20 16855584 1 1 50 32 21 16855616 1 1 50 64 22 16855648 1 1 50 96 23 16855680 1 1 50 128 24 16855488 1 1 49 192 25 16855520 1 1 49 224 26 16855552 1 1 50 0 27 16855584 1 1 50 32 28 16855616 1 1 50 64 29 16855648 1 1 50 96 30 16855680 1 1 50 128 31 16855712 1 1 50 160 32 16855520 1 1 49 224 33 16855552 1 1 50 0 34 16855584 1 1 50 32 35 16855616 1 1 50 64 36 16855648 1 1 50 96 37 16855680 1 1 50 128 38 16855712 1 1 50 160 39 16855744 1 1 50 192 40 16855552 1 1 50 0 41 16855584 1 1 50 32 42 16855616 1 1 50 64 43 16855648 1 1 50 96 44 16855680 1 1 50 128 45 16855712 1 1 50 160 46 16855744 1 1 50 192 47 16855776 1 1 50 224 48 16855584 1 1 50 32 49 16855616 1 1 50 64 50 16855648 1 1 50 96 51 16855680 1 1 50 128 52 16855712 1 1 50 160 53 16855744 1 1 50 192 54 16855776 1 1 50 224 55 16855808 1 1 51 0 56 16855616 1 1 50 64 57 16855648 1 1 50 96 58 16855680 1 1 50 128 59 16855712 1 1 50 160 60 16855744 1 1 50 192 61 16855776 1 1 50 224 62 16855808 1 1 51 0 63 16855840 1 1 51 32 64 16855648 1 1 50 96 65 16855680 1 1 50 128 66 16855712 1 1 50 160 67 16855744 1 1 50 192 68 16855776 1 1 50 224 69 16855808 1 1 51 0 70 16855840 1 1 51 32 71 16855872 1 1 51 64 72 16855680 1 1 50 128 73 16855712 1 1 50 160 74 16855744 1 1 50 192 75 16855776 1 1 50 224 76 16855808 1 1 51 0 77 16855840 1 1 51 32 78 16855872 1 1 51 64 79 16855904 1 1 51 96 80 16855712 1 1 50 160 81 16855744 1 1 50 192 82 16855776 1 1 50 224 83 16855808 1 1 51 0 84 16855840 1 1 51 32 85 16855872 1 1 51 64 86 16855904 1 1 51 96 87 16855936 1 1 51 128 88 16855744 1 1 50 192 89 16855776 1 1 50 224 90 16855808 1 1 51 0 91 16855840 1 1 51 32 92 16855872 1 1 51 64 93 16855904 1 1 51 96 94 16855936 1 1 51 128 95 16855968 1 1 51 160 96 16855776 1 1 50 224 97 16855808 1 1 51 0 98 16855840 1 1 51 32 99 16855872 1 1 51 64 100 16855904 1 1 51 96 101 16855936 1 1 51 128 102 16855968 1 1 51 160 103 16856000 1 1 51 192 104 16855808 1 1 51 0 105 16855840 1 1 51 32 106 16855872 1 1 51 64 107 16855904 1 1 51 96 108 16855936 1 1 51 128 109 16855968 1 1 51 160 110 16856000 1 1 51 192 111 16856032 1 1 51 224 112 16855840 1 1 51 32 113 16855872 1 1 51 64 114 16855904 1 1 51 96 115 16855936 1 1 51 128 116 16855968 1 1 51 160 117 16856000 1 1 51 192 118 16856032 1 1 51 224 119 16856064 1 1 52 0 120 16855872 1 1 51 64 121 16855904 1 1 51 96 122 16855936 1 1 51 128 123 16855968 1 1 51 160 124 16856000 1 1 51 192 125 16856032 1 1 51 224 126 16856064 1 1 52 0 127 16856096 1 1 52 32 128 16855904 1 1 51 96 129 16855936 1 1 51 128 130 16855968 1 1 51 160 131 16856000 1 1 51 192 132 16856032 1 1 51 224 133 16856064 1 1 52 0 134 16856096 1 1 52 32 135 16856128 1 1 52 64 136 16855936 1 1 51 128 137 16855968 1 1 51 160 138 16856000 1 1 51 192 139 16856032 1 1 51 224 140 16856064 1 1 52 0 141 16856096 1 1 52 32 142 16856128 1 1 52 64 143 16856160 1 1 52 96 144 16855968 1 1 51 160 145 16856000 1 1 51 192 146 16856032 1 1 51 224 147 16856064 1 1 52 0 148 16856096 1 1 52 32 149 16856128 1 1 52 64 150 16856160 1 1 52 96 151 16856192 1 1 52 128 152 16856000 1 1 51 192 153 16856032 1 1 51 224 154 16856064 1 1 52 0 155 16856096 1 1 52 32 156 16856128 1 1 52 64 157 16856160 1 1 52 96 158 16856192 1 1 52 128 159 16856224 1 1 52 160 160 16856032 1 1 51 224 161 16856064 1 1 52 0 162 16856096 1 1 52 32 163 16856128 1 1 52 64 164 16856160 1 1 52 96 165 16856192 1 1 52 128 166 16856224 1 1 52 160 167 16856256 1 1 52 192 168 16856064 1 1 52 0 169 16856096 1 1 52 32 170 16856128 1 1 52 64 171 16856160 1 1 52 96 172 16856192 1 1 52 128 173 16856224 1 1 52 160 174 16856256 1 1 52 192 175 16856288 1 1 52 224 176 16856096 1 1 52 32 177 16856128 1 1 52 64 178 16856160 1 1 52 96 179 16856192 1 1 52 128 180 16856224 1 1 52 160 181 16856256 1 1 52 192 182 16856288 1 1 52 224 183 16856320 1 1 53 0 184 16856128 1 1 52 64 185 16856160 1 1 52 96 186 16856192 1 1 52 128 187 16856224 1 1 52 160 188 16856256 1 1 52 192 189 16856288 1 1 52 224 190 16856320 1 1 53 0 192 16856160 1 1 52 96 193 16856192 1 1 52 128 194 16856224 1 1 52 160 195 16856256 1 1 52 192 196 16856288 1 1 52 224 197 16856320 1 1 53 0 200 16856192 1 1 52 128 201 16856224 1 1 52 160 202 16856256 1 1 52 192 203 16856288 1 1 52 224 204 16856320 1 1 53 0 208 16856224 1 1 52 160 209 16856256 1 1 52 192 210 16856288 1 1 52 224 211 16856320 1 1 53 0 216 16856256 1 1 52 192 217 16856288 1 1 52 224 218 16856320 1 1 53 0 224 16856288 1 1 52 224 225 16856320 1 1 53 0 232 16856320 1 1 53 0 Was stuck on this for a couple of days.

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  • OpenCV: Shift/Align face image relative to reference Image (Image Registration)

    - by Abhischek
    I am new to OpenCV2 and working on a project in emotion recognition and would like to align a facial image in relation to a reference facial image. I would like to get the image translation working before moving to rotation. Current idea is to run a search within a limited range on both x and y coordinates and use the sum of squared differences as error metric to select the optimal x/y parameters to align the image. I'm using the OpenCV face_cascade function to detect the face images, all images are resized to a fixed (128x128). Question: Which parameters of the Mat image do I need to modify to shift the image in a positive/negative direction on both x and y axis? I believe setImageROI is no longer supported by Mat datatypes? I have the ROIs for both faces available however I am unsure how to use them. void alignImage(vector<Rect> faceROIstore, vector<Mat> faceIMGstore) { Mat refimg = faceIMGstore[1]; //reference image Mat dispimg = faceIMGstore[52]; // "displaced" version of reference image //Rect refROI = faceROIstore[1]; //Bounding box for face in reference image //Rect dispROI = faceROIstore[52]; //Bounding box for face in displaced image Mat aligned; matchTemplate(dispimg, refimg, aligned, CV_TM_SQDIFF_NORMED); imshow("Aligned image", aligned); } The idea for this approach is based on Image Alignment Tutorial by Richard Szeliski Working on Windows with OpenCV 2.4. Any suggestions are much appreciated.

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  • strange UnindexedFileException for Expression Encoder MediaItem

    - by George2
    Hello everyone, When I use the following statement to create a new instance of MediaItem (VSTS 2008 + .Net 3.5 + C# + Windows 7), and I met with the following exception, any ideas what is wrong? I have tried with other wmv files, and there are no such issues. BTW: I am using Expression Encoder 3 SDK. MediaItem video = new MediaItem("1.wmv"); Microsoft.Expression.Encoder.UnindexedFileException {"Cannot seek file."} thanks in advance, George

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  • How to overwrite i-frames of a video?

    - by Dominik
    I want to destroy all i-frames of a video. Doing this I want to check if encrypting only the i-frames of a video would be sufficient for making it unwatchable. How can I do this? Only removing them and recompressing the video would not be the same as really overwriting the i-frame in the stream without recalculating b-frames etc.

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  • Biometric implementation in Java application and Image Comparision

    - by harigm
    How do I compare the 2 images in Java based web application. I have installed the Biometric thumb reader, I need to read the user Thumb and compare it with his thumb image which is captured during the registration process. Initially I am storing the image in the Mysql as Blob. Else I can store that image in a separate folder as well Please suggest which is best way to do 1)Shall i Use the Java script 2)Is there any built in Java API to perform this

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  • In a digital photo, how can I detect if a mountain is obscured by clouds?

    - by Gavin Brock
    The problem I have a collection of digital photos of a mountain in Japan. However the mountain is often obscured by clouds or fog. What techniques can I use to detect that the mountain is visible in the image? I am currently using Perl with the Imager module, but open to alternatives. All the images are taken from the exact same position - these are some samples. My naïve solution I started by taking several horizontal pixel samples of the mountain cone and comparing the brightness values to other samples from the sky. This worked well for differentiating good image 1 and bad image 2. However in the autumn it snowed and the mountain became brighter than the sky, like image 3, and my simple brightness test started to fail. Image 4 is an example of an edge case. I would classify this as a good image since some of the mountain is clearly visible. UPDATE 1 Thank you for the suggestions - I am happy you all vastly over-estimated my competence. Based on the answers, I have started trying the ImageMagick edge-detect transform, which gives me a much simpler image to analyze. convert sample.jpg -edge 1 edge.jpg I assume I should use some kind of masking to get rid of the trees and most of the clouds. Once I have the masked image, what is the best way to compare the similarity to a 'good' image? I guess the "compare" command suited for this job? How do I get a numeric 'similarity' value from this?

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  • How to write PIL image filter for plain pgm format?

    - by Juha
    How can I write a filter for python imaging library for pgm plain ascii format (P2). Problem here is that basic PIL filter assumes constant number of bytes per pixel. My goal is to open feep.pgm with Image.open(). See http://netpbm.sourceforge.net/doc/pgm.html or below. Alternative solution is that I find other well documented ascii grayscale format that is supported by PIL and all major graphics programs. Any suggestions? br, Juha feep.pgm: P2 # feep.pgm 24 7 15 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3 3 3 3 0 0 7 7 7 7 0 0 11 11 11 11 0 0 15 15 15 15 0 0 3 0 0 0 0 0 7 0 0 0 0 0 11 0 0 0 0 0 15 0 0 15 0 0 3 3 3 0 0 0 7 7 7 0 0 0 11 11 11 0 0 0 15 15 15 15 0 0 3 0 0 0 0 0 7 0 0 0 0 0 11 0 0 0 0 0 15 0 0 0 0 0 3 0 0 0 0 0 7 7 7 7 0 0 11 11 11 11 0 0 15 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 edit: Thanks for the answer, I works... but I need a solution that uses Image.open(). Most of python programs out there use PIL for graphics manipulation (google: python image open). Thus, I need to be able to register a filter to PIL. Then, I can use any software that uses PIL. I now think mostly scipy, pylab, etc. dependent programs.

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  • Stripe suppression algorithm needed

    - by maximus
    I have images with text. There are dark stripes in image that still exists in binary image too. That makes characters connected with that stripe - it can be vertical or horizontal (or at some angle) I need to remove them from image at first, and then to binarize. I've seen bandpass filter in ImageJ program that have some options like - suppress horizontal stripes, and it works good, but it also apply a bandpass filtering. So any idea please how to do it. I think it should be done in frequency domain.

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  • Question on multi-probe Local Sensitive Hashing

    - by Yijinsei
    Hey guys sorry to be asking this kind noob question, but because I really need some guidance on how to use Multi probe LSH pretty urgently, so I did not do much research myself. I realize there is a lib call LSHKIT available that implemented that algorithm, but I have trouble trying to figure out how to use it. Right now, I have a few thousand feature vector 296 dimension, each representing an image. The vector is used to query an user input image, to retrieve the most similar image. The method I used to derive the distance between vector is euclidean distance. I know this might be a rather noob question, but do you guys have knowledge on how should i implement multi probe LSH? I am really very grateful to any answer or response.

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  • Why aren't APT generated classes being compiled by Eclipse?

    - by yamsha
    In my Eclipse project I'm using a third-party annotation processor, Hibernate Metamodel Generator to be exact. The annotation processor works as expected and generates files as specified by the spec. These files are generated inside the directory of the Eclipse project under a "gen" folder. In the project properties this is correctly reflected since two source folders exist - "src" and "gen." However, when the project is built for some reason all the [generated] sources under "gen" are not compiled (checking the "bin" directory I only see .class file from the "src" directory). Does anyone know why this is happening?

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  • On-the-fly lossless image compression

    - by geschema
    I have an embedded application where an image scanner sends out a stream of 16-bit pixels that are later assembled to a grayscale image. As I need to both save this data locally and forward it to a network interface, I'd like to compress the data stream to reduce the required storage space and network bandwidth. Is there a simple algorithm that I can use to losslessly compress the pixel data? I first thought of computing the difference between two consecutive pixels and then encoding this difference with a Huffman code. Unfortunately, the pixels are unsigned 16-bit quantities so the difference can be anywhere in the range -65535 .. +65535 which leads to potentially huge codeword lengths. If a few really long codewords occur in a row, I'll run into buffer overflow problems.

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  • Shared value in parallel python

    - by Jonathan
    Hey all- I'm using ParallelPython to develop a performance-critical script. I'd like to share one value between the 8 processes running on the system. Please excuse the trivial example but this illustrates my question. def findMin(listOfElements): for el in listOfElements: if el < min: min = el import pp min = 0 myList = range(100000) job_server = pp.Server() f1 = job_server.submit(findMin, myList[0:25000]) f2 = job_server.submit(findMin, myList[25000:50000]) f3 = job_server.submit(findMin, myList[50000:75000]) f4 = job_server.submit(findMin, myList[75000:100000]) The pp docs don't seem to describe a way to share data across processes. Is it possible? If so, is there a standard locking mechanism (like in the threading module) to confirm that only one update is done at a time? l = Lock() if(el < min): l.acquire if(el < min): min = el l.release I understand I could keep a local min and compare the 4 in the main thread once returned, but by sharing the value I can do some better pruning of my BFS binary tree and potentially save a lot of loop iterations. Thanks- Jonathan

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  • In a digital photo, detecting if a mountain is obscured by clouds.

    - by Gavin Brock
    The problem I have a collection of digital photos of a mountain in Japan. However the mountain is often obscured by clouds or fog. What techniques can I use to detect that the mountain is visible in the image? I am currently using Perl with the Imager module, but open to alternatives. All the images are taken from the exact same position - these are some samples. My naïve solution I started by taking several horizontal pixel samples of the mountain cone and comparing the brightness values to other samples from the sky. This worked well for differentiating good image 1 and bad image 2. However in the autumn it snowed and the mountain became brighter than the sky, like image 3, and my simple brightness test started to fail. Image 4 is an example of an edge case. I would classify this as a good image since some of the mountain is clearly visible.

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