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  • Copy Small Bitmaps on to Large Bitmap with Transparency Blend: What is faster than graphics.DrawImag

    - by Glenn
    I have identified this call as a bottleneck in a high pressure function. graphics.DrawImage(smallBitmap, x , y); Is there a faster way to blend small semi transparent bitmaps into a larger semi transparent one? Example Usage: XY[] locations = GetLocs(); Bitmap[] bitmaps = GetBmps(); //small images sizes vary approx 30px x 30px using (Bitmap large = new Bitmap(500, 500, PixelFormat.Format32bppPArgb)) using (Graphics largeGraphics = Graphics.FromImage(large)) { for(var i=0; i < largeNumber; i++) { //this is the bottleneck largeGraphics.DrawImage(bitmaps[i], locations[i].x , locations[i].y); } } var done = new MemoryStream(); large.Save(done, ImageFormat.Png); done.Position = 0; return (done); The DrawImage calls take a small 32bppPArgb bitmaps and copies them into a larger bitmap at locations that vary and the small bitmaps might only partially overlap the larger bitmaps visible area. Both images have semi transparent contents that get blended by DrawImage in a way that is important to the output. I've done some testing with BitBlt but not seen significant speed improvement and the alpha blending didn't come out the same in my tests. I'm open to just about any method including a better call to bitblt or unsafe c# code.

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  • Would this method work to scale out SQL queries?

    - by David
    I have a database containing a single huge table. At the moment a query can take anything from 10 to 20 minutes and I need that to go down to 10 seconds. I have spent months trying different products like GridSQL. GridSQL works fine, but is using its own parser which does not have all the needed features. I have also optimized my database in various ways without getting the speedup I need. I have a theory on how one could scale out queries, meaning that I utilize several nodes to run a single query in parallel. The idea is to take an incoming SQL query and simply run it exactly like it is on all the nodes. When the results are returned to a coordinator node, the same query is run on the union of the resultsets. I realize that an aggregate function like average need to be rewritten into a count and sum to the nodes and that the coordinator divides the sum of the sums with the sum of the counts to get the average. What kinds of problems could not easily be solved using this model. I believe one issue would be the count distinct function. Edit: I am getting so many nice suggestions, but none have addressed the method.

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  • Resizing Images with ASP.NET and saving to Database

    - by Ryan
    I need to take an uploaded image, resize it, and save it to the database. Simple enough, except I don't have access to save any temp files to the server. I'm taking the image, resizing it as a Bitmap, and need to save it to a database field as the original image type (JPG for example). How can I get the FileBytes() like this, so I can save it to the database? Before I was using ImageUpload.FileBytes() but now that I'm resizing I'm dealing with Images and Bitmaps instead of FileUploads and can't seem find anything that will give me the bytes. Thanks!

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  • Parallel version of loop not faster than serial version

    - by Il-Bhima
    I'm writing a program in C++ to perform a simulation of particular system. For each timestep, the biggest part of the execution is taking up by a single loop. Fortunately this is embarassingly parallel, so I decided to use Boost Threads to parallelize it (I'm running on a 2 core machine). I would expect at speedup close to 2 times the serial version, since there is no locking. However I am finding that there is no speedup at all. I implemented the parallel version of the loop as follows: Wake up the two threads (they are blocked on a barrier). Each thread then performs the following: Atomically fetch and increment a global counter. Retrieve the particle with that index. Perform the computation on that particle, storing the result in a separate array Wait on a job finished barrier The main thread waits on the job finished barrier. I used this approach since it should provide good load balancing (since each computation may take differing amounts of time). I am really curious as to what could possibly cause this slowdown. I always read that atomic variables are fast, but now I'm starting to wonder whether they have their performance costs. If anybody has some ideas what to look for or any hints I would really appreciate it. I've been bashing my head on it for a week, and profiling has not revealed much.

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  • How to mask part of an image in matlab ?

    - by ZaZu
    Hey guys, I would like to know how to mask part of an image that is in BLACK & WHITE ? I got an object that needs to be edge detected, but I have other white interfering objects in the background that are below the target objet ... I would like to mask the entire lower part of an image to black, how can I do that ? Thanks !!

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  • Creating thumbnails PHP problem

    - by Wayne
    I have this source code where I got it from net tutsplus. I have configured it and made it work in one PHP file. It does work by transferring the original image, but it does not generate to the thumbnails folder. <?php $final_width_of_image = 100; $path_to_image_directory = "../../img/events/" . urldecode($_GET['name']) . "/"; $path_to_thumbs_directory = "../../img/events/" . urldecode($_GET['name']) . "/thumbnails/"; function createThumbnail($filename) { if(preg_match('/[.](jpg)$/', $filename)) { $im = imagecreatefromjpeg($path_to_image_directory . $filename); } elseif(preg_match('/[.](gif)$/', $filename)) { $im = imagecreatefromgif($path_to_image_directory . $filename); } elseif(preg_match('/[.](png)$/', $filename)) { $im = imagecreatefrompng($path_to_image_directory . $filename); } $ox = imagesx($im); $oy = imagesy($im); $nx = $final_width_of_image; $ny = floor($oy * ($final_width_of_image / $ox)); $nm = imagecreatetruecolor($nx, $ny); imagecopyresized($nm, $im, 0,0,0,0,$nx,$ny,$ox,$oy); imagejpeg($nm, $path_to_thumbs_directory . $filename); $tn = '<img src="' . $path_to_thumbs_directory . $filename . '" alt="image" />'; echo $tn; } if(isset($_FILES['fupload'])) { if(preg_match('/[.](jpg)|(gif)|(png)$/', $_FILES['fupload']['name'])) { $filename = $_FILES['fupload']['name']; $source = $_FILES['fupload']['tmp_name']; $target = $path_to_image_directory . $filename; move_uploaded_file($source, $target); createThumbnail($filename); } } ?> Basically it is supposed to generate a thumbnail of the uploaded image and store the original image into a different folder. The paths are correct, it works by getting the folder name in the URL, it does work, but nothing works for the thumbnails folder. BEFORE you ask this related question, yes, thumbnails generation does work on my server by the PHP GD, I have tested it separately. So this is not the problem. :) How do I get this to work? :(

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  • Fastest way to compute a "Visual" checksum of an image

    - by ensnare
    I'm looking to create an ID system for cataloging images. I can't use md5() since that will change if I alter the EXIF tags of the image. I am currently using the SHA1 checksum computed by imagemagick. It works perfectly, but it's really, really slow on larger images (~15 seconds on a quad-core xeon for a 21 megapixel JPG). Are there any other "visual" methods of uniquely identifying an image that would be faster? Thank you.

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  • parallel computation for an Iterator of elements in Java

    - by Brian Harris
    I've had the same need a few times now and wanted to get other thoughts on the right way to structure a solution. The need is to perform some operation on many elements on many threads without needing to have all elements in memory at once, just the ones under computation. As in, Iterables.partition is insufficient because it brings all elements into memory up front. Expressing it in code, I want to write a BulkCalc2 that does the same thing as BulkCalc1, just in parallel. Below is sample code that illustrates my best attempt. I'm not satisfied because it's big and ugly, but it does seem to accomplish my goals of keeping threads highly utilized until the work is done, propagating any exceptions during computation, and not having more than numThreads instances of BigThing necessarily in memory at once. I'll accept the answer which meets the stated goals in the most concise way, whether it's a way to improve my BulkCalc2 or a completely different solution. interface BigThing { int getId(); String getString(); } class Calc { // somewhat expensive computation double calc(BigThing bigThing) { Random r = new Random(bigThing.getString().hashCode()); double d = 0; for (int i = 0; i < 100000; i++) { d += r.nextDouble(); } return d; } } class BulkCalc1 { final Calc calc; public BulkCalc1(Calc calc) { this.calc = calc; } public TreeMap<Integer, Double> calc(Iterator<BigThing> in) { TreeMap<Integer, Double> results = Maps.newTreeMap(); while (in.hasNext()) { BigThing o = in.next(); results.put(o.getId(), calc.calc(o)); } return results; } } class SafeIterator<T> { final Iterator<T> in; SafeIterator(Iterator<T> in) { this.in = in; } synchronized T nextOrNull() { if (in.hasNext()) { return in.next(); } return null; } } class BulkCalc2 { final Calc calc; final int numThreads; public BulkCalc2(Calc calc, int numThreads) { this.calc = calc; this.numThreads = numThreads; } public TreeMap<Integer, Double> calc(Iterator<BigThing> in) { ExecutorService e = Executors.newFixedThreadPool(numThreads); List<Future<?>> futures = Lists.newLinkedList(); final Map<Integer, Double> results = new MapMaker().concurrencyLevel(numThreads).makeMap(); final SafeIterator<BigThing> it = new SafeIterator<BigThing>(in); for (int i = 0; i < numThreads; i++) { futures.add(e.submit(new Runnable() { @Override public void run() { while (true) { BigThing o = it.nextOrNull(); if (o == null) { return; } results.put(o.getId(), calc.calc(o)); } } })); } e.shutdown(); for (Future<?> future : futures) { try { future.get(); } catch (InterruptedException ex) { // swallowing is OK } catch (ExecutionException ex) { throw Throwables.propagate(ex.getCause()); } } return new TreeMap<Integer, Double>(results); } }

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  • minimum enclosing rectangle of fixed aspect ratio

    - by Ramya Narasimha
    I have an Image with many rectangles at different positions in the image and of different sizes (both overlapping and non-overlapping). I also have a non-negative scores associated with each of these rectangles. My problem now is to find one larger rectangle *of a fixed (given) aspect ratio* that encloses as many of these rectangles as possible. I am looking for an algorithm to do this, if anyone has a solution, even a partial one it would be helpful. Please note that the positions of the rectangles in the image is fixed and cannot be moved around and there is no orientation issue as all of them are upright.

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  • PHP image resize and rounded image corners dynamically

    - by Dan
    I'm working of a script that dynamically ads rounded edges to an image then crops it down to a certain size. At the moment the script ads the rounded edges to the picture but i cannot get it so the original image is resized to fit within the dimensons of the final outputted image (140px x 120px) The problem is that the orginal uploaded image depending on it's orginal dimensions change the size it is in the final PNG { $image_file = $_FILES['image']['tmp_name']; $corner_radius = isset($_GET['radius']) ? $_GET['radius'] : 20; // The default corner radius is set to 20px $topleft = (isset($_GET['topleft']) and $_GET['topleft'] == "no") ? false : true; // Top-left rounded corner is shown by default $bottomleft = (isset($_GET['bottomleft']) and $_GET['bottomleft'] == "no") ? false : true; // Bottom-left rounded corner is shown by default $bottomright = (isset($_GET['bottomright']) and $_GET['bottomright'] == "no") ? false : true; // Bottom-right rounded corner is shown by default $topright = (isset($_GET['topright']) and $_GET['topright'] == "no") ? false : true; // Top-right rounded corner is shown by default $imagetype=$_FILES['image']['type']; $endsize=$corner_radius; $startsize=$endsize*3-1; $arcsize=$startsize*2+1; if (($imagetype=='image/jpeg') or ($imagetype=='jpg')) { $image = imagecreatefromjpeg($image_file); } else { if (($imagetype=='GIF') or ($imagetype=='gif')) { $image = imagecreatefromgif($image_file); } else { $image = imagecreatefrompng($image_file); } } $forecolor ='#ffffff'; $size = getimagesize($image_file); // Top-left corner $background = imagecreatetruecolor($size[0],$size[1]); imagecopymerge($background, $image, 0, 0, 0, 0, $size[0], $size[1], 100); $startx=$size[0]*2-1; $starty=$size[1]*2-1; $im_temp = imagecreatetruecolor($startx,$starty); imagecopyresampled($im_temp, $background, 0, 0, 0, 0, $startx, $starty, $size[0], $size[1]); $bg = imagecolorallocate($im_temp, 255,255,255); $fg = imagecolorallocate($im_temp, 255,255,255); if ($topleft == true) { if(!imagearc($im_temp, $startsize, $startsize, $arcsize, $arcsize, 180,270,$bg))echo "nope"; imagefilltoborder($im_temp,0,0,$bg,$bg); } // Bottom-left corner // Top-right corner if ($topright == true) { imagearc($im_temp, $startx-$startsize, $startsize,$arcsize, $arcsize, 270,360,$bg); imagefilltoborder($im_temp,$startx,0,$bg,$bg); } $image = imagecreatetruecolor(140,120); imagecopyresampled($image, $im_temp, 0, 0, 0, 0, $size[0],$size[1],$starty+1310,$startx+1500); // Output final image if(!imagepng($image,'hello.png')) echo "boo"; if(!imagedestroy($image)) echo "2"; if(!imagedestroy($background)) echo "3"; if(!imagedestroy($im_temp)) echo "4"; } EDIT: My question is how to get the orginal image reized so it fits into the 140 x 120 image that is processed with the rounded edges?

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  • Resize an array of images with OpenCV

    - by amr
    I'm passing an array of images (IplImage**) to an object in C++ using OpenCV. I'm then trying to iterate over that array and resize them all to a fixed size (150x150) I'm doing it this way: for(int i = 0; i< this->numTrainingFaces; i++) { IplImage* frame_copy = cvCreateImage( cvSize(150,150), this->faceImageArray[0]->depth, this->faceImageArray[0]->nChannels ); cout << "Created image" << endl; cvResize(this->faceImageArray[i], frame_copy); cout << "Resized image" << endl; IplImage* grey_image = cvCreateImage( cvSize( frame_copy->width, frame_copy->height ), IPL_DEPTH_8U, 1 ); cout << "Created grey image" << endl; cvCvtColor( frame_copy, grey_image, CV_RGB2GRAY ); cout << "Converted image" << endl; this->faceImageArray[i] = grey_image; cvReleaseImage(&frame_copy); cvReleaseImage(&grey_image); } But I'm getting this output, and I'm not sure why: Created image Resized image Created grey image Converted image Created image OpenCV Error: Assertion failed (src.type() == dst.type()) in cvResize, file /build/buildd/opencv-2.1.0/src/cv/cvimgwarp.cpp, line 3102 terminate called after throwing an instance of 'cv::Exception' what(): /build/buildd/opencv-2.1.0/src/cv/cvimgwarp.cpp:3102: error: (-215) src.type() == dst.type() in function cvResize Aborted I'm basically just trying to replace the image in the array with the resized one in as few steps as possible. Edit: Revised my code as follows: for(int i = 0; i< this->numTrainingFaces; i++) { IplImage* frame_copy = cvCreateImage( cvSize(150,150), this->faceImageArray[i]->depth, this->faceImageArray[i]->nChannels ); cvResize(this->faceImageArray[i], frame_copy); IplImage* grey_image = cvCreateImage( cvSize( frame_copy->width, frame_copy->height ), IPL_DEPTH_8U, 1 ); cvCvtColor( frame_copy, grey_image, CV_RGB2GRAY ); faceImageArray[i] = cvCreateImage( cvSize(grey_image->width, grey_image->height), grey_image->depth, grey_image->nChannels); cvCopy(grey_image,faceImageArray[i]); cvReleaseImage(&frame_copy); cvReleaseImage(&grey_image); } Then later on I'm performing some PCA, and get this output: OpenCV Error: Null pointer (Null pointer to the written object) in cvWrite, file /build/buildd/opencv-2.1.0/src/cxcore/cxpersistence.cpp, line 4740 But I don't think my code has got to the point where I'm explicitly calling cvWrite, so it must be part of the library. I can give a full implementation if necessary - is there anything in my code that's going to create a null pointer?

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  • How would I detect horizontal-black lines using ImageMagick?

    - by Zando
    So I have what is essentially a spreadsheet in TIFF format. There is some uniformity to it...for example, all the column widths are the same. I want to de-limit this sheet by those known-column widths and basically create lots of little graphic files, one for each cell, and run OCR on them and store it into a database. The problem is that the horizontal lines are not all the same height, so I need to use some kind of graphics library command to check if every pixel across is the same color (i.e. black). And if so, then I know I've reached the height-delimiter for a cell. How would I go about doing that? (I'm using RMagick)

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  • Finding a small image in a bigger one

    - by tur1ng
    Given an image with a large dimension ( 1.000 x 1.000). What is a good approach to find a small image (e.g. 50 x 50) in the big one? The smaller image can be rotated and differ in the size, but only with a 1:1 ratio. It's not related to any programming language - I'm just interested in pattern recognition. Thank you.

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  • Generate an image / thumbnail of a webpage using X/Gui-less linux

    - by dassouki
    There are a lot of solutions out there on generating a thumbnail or an image preview of a webpage. Some of these are websites like websnapshots, windows libraries such as PHP's imagegrabscreen (only works on windows), and KDE's wkhtml. Many more do exist. However, I'm looking for a GUI-less solution. Something I can create an API around and link it to php or python. I'm comfortable with python, php, C, and shell. This is a personal project, so I'm not interested in commercial applications as I'm aware of their existence. Any ideas?

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  • Who do you use for a merchant account?

    - by Josh
    Hi everyone, I was hoping to get an idea of the merchant accounts out there and if there are any strong recommendations for one in particular. I would also appreciate advice on how merchant accounts differ. Please use separate answers for each recommendation so that we can take full advantage of the voting system. Thanks!

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  • Reading Character from Image

    - by Chinjoo
    I am working on an application which requires matching of numbers from a scanned image file to database entry and update the database with the match result. Say I have image- employee1.jpg. This image will have two two handwritten entries - Employee number and the amount to be paid to the employee. I have to read the employee number from the image and query the database for the that number, update the employee with the amount to be paid as got from the image. Both the employee number and amount to be paid are written inside two boxes at a specified place on the image. Is there any way to automate this. Basically I want a solution in .net using c#. I know this can be done using artificial neural networks. Any ideas would be much appreciated.

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  • filter that uses elements from two arrays at the same time

    - by Gacek
    Let's assume we have two arrays of the same size - A and B. Now, we need a filter that, for a given mask size, selects elements from A, but removes the central element of the mask, and inserts there corresponding element from B. So the 3x3 "pseudo mask" will look similar to this: A A A A B A A A A Doing something like this for averaging filter is quite simple. We can compute the mean value for elements from A without the central element, and then combine it with a proper proportion with elements from B: h = ones(3,3); h(2,2) =0; h = h/sum(h(:)); A_ave = filter2(h, A); C = (8/9) * A_ave + (1/9) * B; But how to do something similar for median filter (medfilt2 or even better for ordfilt2)

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  • Detect Rotation of a scanned image in C#

    - by ahmed fouad
    We want a c# solution to correct the scanned image because it is rotated. To solve this problem we must detect the rotation angle first and then rotate the image. This was our first thought for our problem. But then we thought image warping would be more accurate as I think it would make the scanned image like our template. Then we can process it as we know all the coordinates of our template... I searched for a free SDK or a free solution in c#. Helping me in this will be great as it is the last task in our work. Really, thanks for all.

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  • Java: Line appears when using AffineTransform to scale image

    - by Malakim
    Hi, I'm having a problem with image scaling. When I use the following code to scale an image it ends up with a line either at the bottom or on the right side of the image. double scale = 1; if (scaleHeight >= scaleWidth) { scale = scaleWidth; } else { scale = scaleHeight; } AffineTransform af = new AffineTransform(); af.scale(scale, scale); AffineTransformOp operation = new AffineTransformOp(af, AffineTransformOp.TYPE_NEAREST_NEIGHBOR); BufferedImage bufferedThumb = operation.filter(img, null); The original image is here: http://tinyurl.com/yzv6r7h The scaled image: http://tinyurl.com/yk6e8ga Does anyone know why the line appears? Thanks!

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