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  • uneven illuminated images

    - by coul
    How to get rid of uneven illumination from images, that contain text data, usually printed but may be handwritten? It can have some spots of lights because the light reflected while making picture. I've seen the Halcon program's segment_characters function that is doing this work perfectly, but it is not open source. I wish to convert an image to the image that has a constant illumination at background and more dark colored regions of text. So that binarization will be easy and without noise. The text is assumed to be dark colored than it's background. Any ideas?

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  • Saving a remote image with cURL?

    - by thebluefox
    Morning all, Theres a few questions around this but none that really answer my question, as far as I ca understand. Basically I have a GD script that deals with resizing and caching images on our server, but I need to do the same with images stored on a remote server. So, I'm wanting to save the image locally, then resize and display it as normal. I've got this far... $file_name_array = explode('/', $filename); $file_name_array_r = array_reverse($file_name_array); $save_to = 'system/cache/remote/'.$file_name_array_r[1].'-'.$file_name_array_r[0]; $ch = curl_init($filename); $fp = fopen($save_to, "wb"); // set URL and other appropriate options $options = array(CURLOPT_FILE => $fp, CURLOPT_HEADER => 0, CURLOPT_FOLLOWLOCATION => 1, CURLOPT_TIMEOUT => 60); // 1 minute timeout (should be enough) curl_setopt_array($ch, $options); curl_exec($ch); curl_close($ch); fclose($fp); This creates the image file, but does not copy it accross? Am I missing the point? Cheers guys.

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  • function taking in an input image and different kernel size

    - by drifterOcean19
    I have this filtering function that takes an input image, performs convolution using a given kernel, and returns the resulting image. However, I can't seem to work it out how to make it takes different kernel sizes.For example instead of pre-defined 3x3 kernel as below in the code, it could instead take 5x5 or 7x7. and then the user could input the type of kernel/filter they want(Depending on the intended effect). I can't seem to put my head around it. i'm quite new to matlab. function [newImg] = kernelFunc(imgB) img=imread(imgB); figure,imshow(img); img2=zeros(size(img)+2); newImg=zeros(size(img)); for rgb=1:3 for x=1:size(img,1) for y=1:size(img,2) img2(x+1,y+1,rgb)=img(x,y,rgb); end end end for rgb=1:3 for i= 1:size(img2,1)-2 for j=1:size(img2,2)-2 window=zeros(9,1); inc=1; for x=1:3 for y=1:3 window(inc)=img2(i+x-1,j+y-1,rgb); inc=inc+1; end end kernel=[1;2;1;2;4;2;1;2;1]/16; med=window.*kernel; disp(med); med=sum(med); med=floor(med); newImg(i,j,rgb)=med; end end end newImg=uint8(newImg); figure,imshow(newImg); end

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  • png image blurry when loaded onto texture

    - by Chris
    I have created a png image in photoshop with transparencies that I have loaded into and OpenGL program. I have binded it to a texture and in the program the picture looks blurry and I'm not sure why. Loading Code // Texture loading object nv::Image title; // Return true on success if(title.loadImageFromFile("test.png")) { glGenTextures(1, &titleTex); glBindTexture(GL_TEXTURE_2D, titleTex); glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_TRUE); glTexImage2D(GL_TEXTURE_2D, 0, title.getInternalFormat(), title.getWidth(), title.getHeight(), 0, title.getFormat(), title.getType(), title.getLevel(0)); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAX_ANISOTROPY_EXT, 16.0f); } else MessageBox(NULL, "Failed to load texture", "End of the world", MB_OK | MB_ICONINFORMATION); Display Code glEnable(GL_TEXTURE_2D); glEnable(GL_BLEND); glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); glBindTexture(GL_TEXTURE_2D, titleTex); glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE); glTranslatef(-800, 0, 0.0); glColor3f(1,1,1); glBegin(GL_QUADS); glTexCoord2f(0.0, 0.0); glVertex2f(0,0); glTexCoord2f(0.0, 1.0); glVertex2f(0,600); glTexCoord2f(1.0, 1.0); glVertex2f(1600,600); glTexCoord2f(1.0, 0.0); glVertex2f(1600,0); glEnd(); glDisable(GL_BLEND); glDisable(GL_TEXTURE_2D);

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  • CUDA small kernel 2d convolution - how to do it

    - by paulAl
    I've been experimenting with CUDA kernels for days to perform a fast 2D convolution between a 500x500 image (but I could also vary the dimensions) and a very small 2D kernel (a laplacian 2d kernel, so it's a 3x3 kernel.. too small to take a huge advantage with all the cuda threads). I created a CPU classic implementation (two for loops, as easy as you would think) and then I started creating CUDA kernels. After a few disappointing attempts to perform a faster convolution I ended up with this code: http://www.evl.uic.edu/sjames/cs525/final.html (see the Shared Memory section), it basically lets a 16x16 threads block load all the convolution data he needs in the shared memory and then performs the convolution. Nothing, the CPU is still a lot faster. I didn't try the FFT approach because the CUDA SDK states that it is efficient with large kernel sizes. Whether or not you read everything I wrote, my question is: how can I perform a fast 2D convolution between a relatively large image and a very small kernel (3x3) with CUDA?

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  • Updating an image's ImageUrl within a Repeater

    - by Django Reinhardt
    I hope someone can help me. It's a pretty newbie question, I'm afraid. I have an image inside a repeater, and I would like to change its IMAGEURL based on parameter that's being passed to it. <asp:Repeater ID="Repeater" runat="server"> <HeaderTemplate> <asp:Image ID="imgType" runat="server" /> </HeaderTemplate> <ItemTemplate> <%# Eval("DisplayName")%> </ItemTemplate> <SeparatorTemplate> <hr /> </SeparatorTemplate> </asp:Repeater> There is a SWITCH statement in the code behind that is altering the IMAGEURL depending on what's being passed to it. Inevitably, however, the images ID ("imgType") is not visible to the SWITCH statement (presumably because it's inside a REPEATER). Any suggestions on the best way to implement this would be greatly appreciated. Sorry for such a newbie question.

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  • Image swap with a javascript onclick dropdown menu

    - by AzzyDude
    So I've got this code that has an image and when you click it a dropdown menu appears. Pretty simple. The code works fine but I'm trying to incorporate an image swap on click and I'm having difficulty. Here's the HTML and the JS (there's some CSS too, but I'll leave that out): HTML: <div id="header"> <dl class="dropdown"> <dt><a href="#"><img src="images/cogwheel_btn.png"/></a></dt> <dd> <ul> <li><a href="#">Favorites</a></li> <li><a href="#">History</a></li> </ul> </dd> </dl> </div> JS: $(document).ready(function() { $(".dropdown img.flag").addClass("flagvisibility"); $(".dropdown dt a").click(function() { $(".dropdown dd ul").toggle(); }); $(".dropdown dd ul li a").click(function() { var text = $(this).html(); $(".dropdown dt a span").html(text); $(".dropdown dd ul").hide(); $("#result").html("Selected value is: " + getSelectedValue("sample")); }); function getSelectedValue(id) { return $("#" + id).find("dt a span.value").html(); } $(document).bind('click', function(e) { var $clicked = $(e.target); if (!$clicked.parents().hasClass("dropdown")) $(".dropdown dd ul").hide(); }); $("#flagSwitcher").click(function() { $(".dropdown img.flag").toggleClass("flagvisibility"); }); });? I've tried adding lines like ("dt").empty(); and then ("dt").html("new_image") but it causes the dropdown functionality to stop working. Anyone any ideas?

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  • ASP.NET Image Upload Parameter Not Valid. Exception

    - by pennylane
    Hi Guys, Im just trying to save a file to disk using a posted stream from jquery uploadify I'm also getting Parameter not valid. On adding to the error message so i can tell where it blew up in production im seeing it blow up on: var postedBitmap = new Bitmap(postedFileStream) any help would be most appreciated public string SaveImageFile(Stream postedFileStream, string fileDirectory, string fileName, int imageWidth, int imageHeight) { string result = ""; string fullFilePath = Path.Combine(fileDirectory, fileName); string exhelp = ""; if (!File.Exists(fullFilePath)) { try { using (var postedBitmap = new Bitmap(postedFileStream)) { exhelp += "got past bmp creation" + fullFilePath; using (var imageToSave = ImageHandler.ResizeImage(postedBitmap, imageWidth, imageHeight)) { exhelp += "got past resize"; if (!Directory.Exists(fileDirectory)) { Directory.CreateDirectory(fileDirectory); } result = "Success"; postedBitmap.Dispose(); imageToSave.Save(fullFilePath, GetImageFormatForFile(fileName)); } exhelp += "got past save"; } } catch (Exception ex) { result = "Save Image File Failed " + ex.Message + ex.StackTrace; Global.SendExceptionEmail("Save Image File Failed " + exhelp, ex); } } return result; }

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  • Html image link, not working

    - by Anders Metnik
    Hey I'm doing some testing while learning js + html5 and other web/mobile frameworks. I have a problem with one of my picture links, which I also need to change the picture dynamically and the target(hopefully). But it won't work. HTML: <div data-role="content" id="firstPageContent"> <p>I'm first in the source order so I'm shown as the page.</p> <p>View internal page called <a href="#second">second</a></p> <a href = "#second" id="mapLink" name="mapLink"><img id="mapLinkImage" alt="a map which links to the mapPage" src="images/main_header.png"/></a> <Button id="loadButton" onClick="load()"/> </div><!-- /content --> js: importScripts(dataManager.js); var mapLink=second; function load(){ alert('called'); document.getElementById('mapLinkImage').src="images/store.map.png"; document.getElementById('mapLink').href = "http://google.com"; } problem: It ain't showing the image as a link, just as a plain image. i think this will work now.

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  • Child elements changing opacity with parent Image

    - by mitch
    I have a <div> element which has a background image. On top of that I have some text that is hidden but when the user hovers over the <div> element that text will show and the <div> opacity will lower. My problem is when you hover over the div all elements inside that change opacity as well. I have looked through stackoverflow to see if anyone has the same problem but all i found were answers that had RGBA using background colors (not images). Here is my css: .pic{ background-image:url(http://www.granitesportsinstitute.com/wp-content/uploads/2014/06/Green-Sea-Turtle-150x150.jpg); -webkit-transition: all .3s ease-in-out; -moz-transition: all .3s ease-in-out; -o-transition: all .3s ease-in-out; transition: all .3s ease-in-out; } .textstuff{ visibility:hidden; } .pic:hover .textstuff{ visibility:visible; color:black; } .pic:hover{ filter: alpha(opacity=30); -moz-opacity: 0.3; -khtml-opacity: 0.3; opacity: 0.3; } HTML HERE: <div class="pic" style="height:150px;width:150px;"> <div class="textstuff">this is text</div> </div>

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  • Flex 4: Scale to a point (zoom into an image where the mouse was clicked)

    - by Jason W
    I've been trying to get this working and I can't seem to figure it out. There is an Image control that when I click on it I need to zoom in (using the center/transform point where the mouse is clicked). I have the zoom transition working great, but when I set transformX & tranformY (with autoCenterTransform false) it doesn't zoom into that point. Here is my code that only zooms in (not to a specific point) <fx:Script> <![CDATA[ protected function imgLogo_clickHandler(event:MouseEvent):void { transformer.play(); } ]]> </fx:Script> <fx:Declarations> <s:Parallel id="transformer" target="{imgLogo}"> <s:Scale scaleXBy="0.5" scaleYBy="0.5" /> </s:Parallel> </fx:Declarations> <mx:Image id="imgLogo" width="250" x="100" y="100" maintainAspectRatio="true" source="@Embed('src/logo.png')" click="imgLogo_clickHandler(event)" /> Any help is greatly appreciated. Thanks

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  • How can I center a CSS background image as if the image had a different width (without cutting the bgimg off)?

    - by henrymb67
    I'm attempting to add a bookmarklet to my wop website. The issue is that I would like to have the bookmarklet (highlighted in red in the picture below) centered as if it did not have the arrow sticking out the side. If I change the width of the bgimage in the css, to be the same as the below indented box thingies, it centers how I would like it to. But, it cuts off a bit of the arrow. So, my question is, how can I center the bookmarklet as if it had the width of the other indented box thingies. bookmarklet CSS: #bookmarklet { background-image:url('images/bookmarklet.png'); width:425px; height:175px; background-repeat: no-repeat; margin-left: auto; margin-right: auto; padding-bottom:8px; } I want the bookmarklet to be centered as if it were(without cutting out the side of the arrow): #resultbg { background-image:url('images/resultbg.png'); width:404px; height:347px; background-repeat: no-repeat; margin-left: auto; margin-right: auto; padding-top:8px; } Any help is greatly appreciated! Thank you(:

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  • Adding an expression based image in a client report definition file (RDLC)

    - by rajbk
    In previous posts, I showed you how to create a report using Visual Studio 2010 and how to add a hyperlink to the report.  In this post, I show you how to add an expression based image to each row of the report. This similar to displaying a checkbox column for Boolean values.  A sample project is attached to the bottom of this post. To start off, download the project we created earlier from here.  The report we created had a “Discontinued” column of type Boolean. We are going to change it to display an “available” icon or “unavailable” icon based on the “Discontinued” row value.    Load the project and double click on Products.rdlc. With the report design surface active, you will see the “Report Data” tool window. Right click on the Images folder and select “Add Image..”   Add the available_icon.png and discontinued_icon.png images (the sample project at the end of this post has the icon png files)    You can see the images we added in the “Report Data” tool window.   Drag and drop the available_icon into the “Discontinued” column row (not the header) We get a dialog box which allows us to set the image properties. We will add an expression that specifies the image to display based the “Discontinued” value from the Product table. Click on the expression (fx) button.   Add the following expression : = IIf(Fields!Discontinued.Value = True, “discontinued_icon”, “available_icon”)   Save and exit all dialog boxes. In the report design surface, resize the column header and change the text from “Discontinued” to “In Production”.   (Optional) Right click on the image cell (not header) , go to “Image Properties..” and offset it by 5pt from the left. (Optional) Change the border color since it is not set by default for image columns. We are done adding our image column! Compile the application and run it. You will see that the “In Production” column has red ‘x’ icons for discontinued products. Download the VS 2010 sample project NorthwindReportsImage.zip Other Posts Adding a hyperlink in a client report definition file (RDLC) Rendering an RDLC directly to the Response stream in ASP.NET MVC ASP.NET MVC Paging/Sorting/Filtering using the MVCContrib Grid and Pager Localization in ASP.NET MVC 2 using ModelMetadata Setting up Visual Studio 2010 to step into Microsoft .NET Source Code Running ASP.NET Webforms and ASP.NET MVC side by side Pre-filtering and shaping OData feeds using WCF Data Services and the Entity Framework

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  • My image is not showing in java, using ImageIcon

    - by user1048606
    I'd like to know why my images are now showing up when I use ImageIcon and when I have specified the directory the image is in. All I get is a black blank screen with nothing else on it. import java.awt.Image; import java.awt.event.KeyEvent; import javax.swing.ImageIcon; import java.awt.Image; import java.awt.event.KeyEvent; import java.util.ArrayList; import javax.swing.ImageIcon; // Class for handling key input public class Craft { private int dx; private int dy; private int x; private int y; private Image image; private Image image2; private ArrayList missiles; private final int CRAFT_SIZE = 20; private String craft = "C:\\Users\\Jimmy\\Desktop\\Jimmy's Folder\\programs\\craft.png"; public Craft() { ImageIcon ii = new ImageIcon(craft); image2 = ii.getImage(); missiles = new ArrayList(); x = 40; y = 60; } public void move() { x += dx; y += dy; } public int getX() { return x; } public int getY() { return y; } public Image getImage() { return image; } public ArrayList getMissiles() { return missiles; } public void keyPressed(KeyEvent e) { int key = e.getKeyCode(); // Shooting key if (key == KeyEvent.VK_SPACE) { fire(); } if (key == KeyEvent.VK_LEFT) { dx = -1; } if (key == KeyEvent.VK_RIGHT) { dx = 1; } if (key == KeyEvent.VK_UP) { dy = -1; } if (key == KeyEvent.VK_DOWN) { dy = 1; } } // Handles the missile object firing out of the ship public void fire() { missiles.add(new Missile(x + CRAFT_SIZE, y + CRAFT_SIZE/2)); } public void keyReleased(KeyEvent e) { int key = e.getKeyCode(); if (key == KeyEvent.VK_LEFT) { dx = 0; } if (key == KeyEvent.VK_RIGHT) { dx = 0; } if (key == KeyEvent.VK_UP) { dy = 0; } if (key == KeyEvent.VK_DOWN) { dy = 0; } } }

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  • Gosu ruby windows no allocator for Image [on hold]

    - by user2812818
    I am trying to run the Gosu tutorial on Windows XP for ruby 1.93 It quits with `new': allocator undefined for Gosu::Image (TypeError) when trying to initialize a new Image: require 'gosu' require 'rubygems' class GameWindow < Gosu::Window def initialize super(640, 480, false) self.caption = "Gosu Tutorial Game" @background_image = Gosu::Image.new(self, "/media/123.bmp", true) end end I made sure the image is there and is png/bmp. I know it is something simple, maybe to do with the DLL's required? just not sure what.... thanks sgv

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  • Image captions and wrapping [migrated]

    - by Charles
    What's the best way to add a caption below an image? The image and its caption will be floated right, and the text on the caption needs to wrap -- a 200x200px image shouldn't have a caption of width 800px. I would strongly prefer a solution that allows me to update images (with different widths) without changing the CSS or markup. For reasons beyond my control the image itself will also be floated right, but this should not be too problematic.

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  • Java image conversion to RGB565

    - by Vladimir
    I try to convert image to RGB565 format. I read this image: BufferedImage bufImg = ImageIO.read(imagePathFile); sendImg = new BufferedImage(CONTROLLER_LCD_WIDTH/*320*/, CONTROLLER_LCD_HEIGHT/*240*/, BufferedImage.TYPE_USHORT_565_RGB); sendImg .getGraphics().drawImage(bufImg, 0, 0, CONTROLLER_LCD_WIDTH/*320*/, CONTROLLER_LCD_HEIGHT/*240*/, null); Here is it: Then I convert it to RGB565: int numByte=0; byte[] OutputImageArray = new byte[CONTROLLER_LCD_WIDTH*CONTROLLER_LCD_HEIGHT*2]; int i=0; int j=0; int len = OutputImageArray.length; for (i=0;i<CONTROLLER_LCD_WIDTH;i++) { for (j=0;j<CONTROLLER_LCD_HEIGHT;j++) { Color c = new Color(sendImg.getRGB(i, j)); int aRGBpix = sendImg.getRGB(i, j); int alpha; int red = c.getRed(); int green = c.getGreen(); int blue = c.getBlue(); //RGB888 red = (aRGBpix >> 16) & 0x0FF; green = (aRGBpix >> 8) & 0x0FF; blue = (aRGBpix >> 0) & 0x0FF; alpha = (aRGBpix >> 24) & 0x0FF; //RGB565 red = red >> 3; green = green >> 2; blue = blue >> 3; //A pixel is represented by a 4-byte (32 bit) integer, like so: //00000000 00000000 00000000 11111111 //^ Alpha ^Red ^Green ^Blue //Converting to RGB565 short pixel_to_send = 0; int pixel_to_send_int = 0; pixel_to_send_int = (red << 11) | (green << 5) | (blue); pixel_to_send = (short) pixel_to_send_int; //dividing into bytes byte byteH=(byte)((pixel_to_send >> 8) & 0x0FF); byte byteL=(byte)(pixel_to_send & 0x0FF); //Writing it to array - High-byte is second OutputImageArray[numByte]=byteH; OutputImageArray[numByte+1]=byteL; numByte+=2; } } Then I try to restore this from resulting array OutputImageArray: i=0; j=0; numByte=0; BufferedImage NewImg = new BufferedImage(CONTROLLER_LCD_WIDTH, CONTROLLER_LCD_HEIGHT, BufferedImage.TYPE_USHORT_565_RGB); for (i=0;i<CONTROLLER_LCD_WIDTH;i++) { for (j=0;j<CONTROLLER_LCD_HEIGHT;j++) { int curPixel=0; int alpha=0x0FF; int red; int green; int blue; byte byteL=0; byte byteH=0; byteH = OutputImageArray[numByte]; byteL = OutputImageArray[numByte+1]; curPixel= (byteH << 8) | (byteL); //RGB565 red = (curPixel >> (6+5)) & 0x01F; green = (curPixel >> 5) & 0x03F; blue = (curPixel) & 0x01F; //RGB888 red = red << 3; green = green << 2; blue = blue << 3; //aRGB curPixel = 0; curPixel = (alpha << 24) | (red << 16) | (green << 8) | (blue); NewImg.setRGB(i, j, curPixel); numByte+=2; } } I output this restored image. But I see that it looks very poor. I expected the lost of pictures quality. But as I thought, this picture has to have almost the same quality as the previous picture. - Is it right? Is my code right?

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  • SQL Sentry Truth-Telling and Disk Configuration

    - by AjarnMark
    Recently, SQL Sentry told me something about my SQL Server disk configurations that I just didn’t want to believe, but alas, it was true. Several days ago I posted my First Impressions of the SQL Sentry Power Suite.  Today’s post could fall into the category of, “Hey, as long as you have that fancy tool…”  Unfortunately, it also falls into the category of an overloaded worker taking someone else’s word for the truth, not verifying it with independent fact-checking, and then making decisions based on that.  Here’s my story… I’m not exactly an Accidental DBA (or Involuntary DBA as Paul Randal calls it).  I came to this company five years ago as a lead application developer with extensive experience in database design and development.  I worked my way into management, and along the way, took over the DBA responsibilities.  Fortunately, our systems run pretty smoothly most of the time, but I’m always looking for ways to make them better and to fit into my understanding of best practices.  When I took over as DBA, I inherited a SQL 2000 server with about 30 databases on it supporting our main systems, and a SQL 2005 server with multiple instances.  Both of these servers were configured with the Operating System and Application files on the C drive, data files on a different drive letter, and log files on a third drive letter.  Even before I took over as DBA, I verified that this was true with a previous server administrator, and that these represented actual separate disks.  He stated that they did, and I thought that all was well. Then one day, I’m poking around inside the SQL Sentry Performance Advisor, checking out features as I am evaluating whether to purchase the product, and I come across a Disk Configuration section.  The first thing I notice is that the drives do not have the proper partition offset, which was not at all surprising to me given the age of the installation and the relative newness of that topic.  But what threw me for a loop was that the graphic display appeared to be telling me that I did not in fact have three separate drives (or arrays) but rather had two, and that the log files were merely on a separate volume on the same physical array as the OS.  I figured that I must be reading it wrong so I scanned the Help file, but that just seemed to confirm my interpretation.  Then I thought, “there must be something wrong with the demo version of the software!  This can’t be right!”  But just to double-check, I went to our current server admin to talk it over with him, and sure enough, SQL Sentry was telling the truth! I was stunned!  I quickly went through the grieving process…denial…anger…reconciliation.  Here was something that I thought was such a basic truth that was turned upside down.  OK, granted, this wasn’t disastrous.  Our databases didn’t suddenly grind to a halt.  I didn’t get calls late at night inquiring about the sudden downturn in performance.  But it was a bit of a shock to the system, in a good way, to jolt me out of taking what I had believed as the truth for granted, and instead to Trust, but Verify! Yes, before someone else points it out, I know that there are”free” disk management tools built-in to Windows that would have told me the same thing if I had only looked at them; I did not have to buy a fancy tool to tell me that, but the fact is, until I was evaluating the tool, I had just gone with what I was told, and never bothered to check what was actually there. So, what things do you believe to be true but you actually never verified?

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  • Organization &amp; Architecture UNISA Studies &ndash; Chap 6

    - by MarkPearl
    Learning Outcomes Discuss the physical characteristics of magnetic disks Describe how data is organized and accessed on a magnetic disk Discuss the parameters that play a role in the performance of magnetic disks Describe different optical memory devices Magnetic Disk The way data is stored on and retried from magnetic disks Data is recorded on and later retrieved form the disk via a conducting coil named the head (in many systems there are two heads) The writ mechanism exploits the fact that electricity flowing through a coil produces a magnetic field. Electric pulses are sent to the write head, and the resulting magnetic patterns are recorded on the surface below with different patterns for positive and negative currents The physical characteristics of a magnetic disk   Summarize from book   The factors that play a role in the performance of a disk Seek time – the time it takes to position the head at the track Rotational delay / latency – the time it takes for the beginning of the sector to reach the head Access time – the sum of the seek time and rotational delay Transfer time – the time it takes to transfer data RAID The rate of improvement in secondary storage performance has been considerably less than the rate for processors and main memory. Thus secondary storage has become a bit of a bottleneck. RAID works on the concept that if one disk can be pushed so far, additional gains in performance are to be had by using multiple parallel components. Points to note about RAID… RAID is a set of physical disk drives viewed by the operating system as a single logical drive Data is distributed across the physical drives of an array in a scheme known as striping Redundant disk capacity is used to store parity information, which guarantees data recoverability in case of a disk failure (not supported by RAID 0 or RAID 1) Interesting to note that the increase in the number of drives, increases the probability of failure. To compensate for this decreased reliability RAID makes use of stored parity information that enables the recovery of data lost due to a disk failure.   The RAID scheme consists of 7 levels…   Category Level Description Disks Required Data Availability Large I/O Data Transfer Capacity Small I/O Request Rate Striping 0 Non Redundant N Lower than single disk Very high Very high for both read and write Mirroring 1 Mirrored 2N Higher than RAID 2 – 5 but lower than RAID 6 Higher than single disk Up to twice that of a signle disk for read Parallel Access 2 Redundant via Hamming Code N + m Much higher than single disk Highest of all listed alternatives Approximately twice that of a single disk Parallel Access 3 Bit interleaved parity N + 1 Much higher than single disk Highest of all listed alternatives Approximately twice that of a single disk Independent Access 4 Block interleaved parity N + 1 Much higher than single disk Similar to RAID 0 for read, significantly lower than single disk for write Similar to RAID 0 for read, significantly lower than single disk for write Independent Access 5 Block interleaved parity N + 1 Much higher than single disk Similar to RAID 0 for read, lower than single disk for write Similar to RAID 0 for read, generally  lower than single disk for write Independent Access 6 Block interleaved parity N + 2 Highest of all listed alternatives Similar to RAID 0 for read; lower than RAID 5 for write Similar to RAID 0 for read, significantly lower than RAID 5  for write   Read page 215 – 221 for detailed explanation on RAID levels Optical Memory There are a variety of optical-disk systems available. Read through the table on page 222 – 223 Some of the devices include… CD CD-ROM CD-R CD-RW DVD DVD-R DVD-RW Blue-Ray DVD Magnetic Tape Most modern systems use serial recording – data is lade out as a sequence of bits along each track. The typical recording used in serial is referred to as serpentine recording. In this technique when data is being recorded, the first set of bits is recorded along the whole length of the tape. When the end of the tape is reached the heads are repostioned to record a new track, and the tape is again recorded on its whole length, this time in the opposite direction. That process continued back and forth until the tape is full. To increase speed, the read-write head is capable of reading and writing a number of adjacent tracks simultaneously. Data is still recorded serially along individual tracks, but blocks in sequence are stored on adjacent tracks as suggested. A tape drive is a sequential access device. Magnetic tape was the first kind of secondary memory. It is still widely used as the lowest-cost, slowest speed member of the memory hierarchy.

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  • How to free up space on /boot? [closed]

    - by Phrogz
    Possible Duplicate: Free up more space on /boot I logged onto my server today to find the message: => /boot is using 98.9% of 91MB When I look at /boot I see that it is indeed very low on space, and has old-kernel files in it: phrogz@planar:~$ df -h /boot Filesystem Size Used Avail Use% Mounted on /dev/sda1 92M 54M 33M 63% /boot phrogz@planar:~$ la /boot total 81880 drwxr-xr-x 4 root root 3072 2011-12-02 06:26 ./ drwxr-xr-x 22 root root 4096 2011-09-29 06:37 ../ -rw-r--r-- 1 root root 646419 2011-03-01 19:02 abi-2.6.32-30-server -rw-r--r-- 1 root root 646419 2011-04-08 17:07 abi-2.6.32-31-server -rw-r--r-- 1 root root 646454 2011-04-20 16:53 abi-2.6.32-32-server -rw-r--r-- 1 root root 646454 2011-07-29 16:07 abi-2.6.32-33-server -rw-r--r-- 1 root root 646710 2011-09-13 18:00 abi-2.6.32-34-server -rw-r--r-- 1 root root 646820 2011-10-11 11:10 abi-2.6.32-35-server -rw-r--r-- 1 root root 110687 2011-03-01 19:02 config-2.6.32-30-server -rw-r--r-- 1 root root 110676 2011-04-08 17:07 config-2.6.32-31-server -rw-r--r-- 1 root root 110687 2011-04-20 16:53 config-2.6.32-32-server -rw-r--r-- 1 root root 110687 2011-07-29 16:07 config-2.6.32-33-server -rw-r--r-- 1 root root 110687 2011-09-13 18:00 config-2.6.32-34-server -rw-r--r-- 1 root root 110687 2011-10-11 11:10 config-2.6.32-35-server drwxr-xr-x 3 root root 6144 2011-12-02 06:26 grub/ -rw-r--r-- 1 root root 8258196 2011-05-18 11:58 initrd.img-2.6.32-30-server -rw-r--r-- 1 root root 8259568 2011-05-23 20:24 initrd.img-2.6.32-31-server -rw-r--r-- 1 root root 8257374 2011-05-30 07:47 initrd.img-2.6.32-32-server -rw-r--r-- 1 root root 8287489 2011-08-10 06:37 initrd.img-2.6.32-33-server -rw-r--r-- 1 root root 8288075 2011-09-29 06:37 initrd.img-2.6.32-34-server drwx------ 2 root root 12288 2011-05-18 11:46 lost+found/ -rw-r--r-- 1 root root 160280 2010-03-23 03:40 memtest86+.bin -rw-r--r-- 1 root root 2179117 2011-03-01 19:02 System.map-2.6.32-30-server -rw-r--r-- 1 root root 2179628 2011-04-08 17:07 System.map-2.6.32-31-server -rw-r--r-- 1 root root 2178240 2011-04-20 16:53 System.map-2.6.32-32-server -rw-r--r-- 1 root root 2178382 2011-07-29 16:07 System.map-2.6.32-33-server -rw-r--r-- 1 root root 2178952 2011-09-13 18:00 System.map-2.6.32-34-server -rw-r--r-- 1 root root 2179333 2011-10-11 11:10 System.map-2.6.32-35-server -rw-r--r-- 1 root root 1336 2011-03-01 19:08 vmcoreinfo-2.6.32-30-server -rw-r--r-- 1 root root 1336 2011-04-08 17:13 vmcoreinfo-2.6.32-31-server -rw-r--r-- 1 root root 1336 2011-04-20 16:54 vmcoreinfo-2.6.32-32-server -rw-r--r-- 1 root root 1336 2011-07-29 16:08 vmcoreinfo-2.6.32-33-server -rw-r--r-- 1 root root 1336 2011-09-13 18:03 vmcoreinfo-2.6.32-34-server -rw-r--r-- 1 root root 1336 2011-10-11 11:11 vmcoreinfo-2.6.32-35-server -rw-r--r-- 1 root root 4111552 2011-03-01 19:02 vmlinuz-2.6.32-30-server -rw-r--r-- 1 root root 4113344 2011-04-08 17:07 vmlinuz-2.6.32-31-server -rw-r--r-- 1 root root 4106528 2011-04-20 16:53 vmlinuz-2.6.32-32-server -rw-r--r-- 1 root root 4107648 2011-07-29 16:07 vmlinuz-2.6.32-33-server -rw-r--r-- 1 root root 4108960 2011-09-13 18:00 vmlinuz-2.6.32-34-server -rw-r--r-- 1 root root 4111040 2011-10-11 11:10 vmlinuz-2.6.32-35-server I was able to find the old kernel packages like so: phrogz@planar:/boot$ dpkg -l | grep linux-image ii linux-image-2.6.32-30-server 2.6.32-30.59 Linux kernel image for version 2.6.32 on x86 ii linux-image-2.6.32-31-server 2.6.32-31.61 Linux kernel image for version 2.6.32 on x86 ii linux-image-2.6.32-32-server 2.6.32-32.62 Linux kernel image for version 2.6.32 on x86 ii linux-image-2.6.32-33-server 2.6.32-33.72 Linux kernel image for version 2.6.32 on x86 ii linux-image-2.6.32-34-server 2.6.32-34.77 Linux kernel image for version 2.6.32 on x86 iF linux-image-2.6.32-35-server 2.6.32-35.78 Linux kernel image for version 2.6.32 on x86 iU linux-image-server 2.6.32.36.42 Linux kernel image on Server Equipment. …and I can see that many of them are older than my current image: phrogz@planar:/boot$ uname -a Linux planar 2.6.32-34-server #77-Ubuntu SMP Tue Sep 13 20:54:38 UTC 2011 x86_64 GNU/Linux However, I can't actually remove them due to an unmet dependency: phrogz@planar:/boot$ sudo apt-get --purge remove linux-image-2.6.32-30-server Reading package lists... Done Building dependency tree Reading state information... Done You might want to run `apt-get -f install' to correct these: The following packages have unmet dependencies: linux-image-server: Depends: linux-image-2.6.32-36-server but it is not going to be installed E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution). But I can't fix the dependency (presumably due to low disk space): phrogz@planar:/boot$ sudo apt-get -f install Reading package lists... Done Building dependency tree Reading state information... Done Correcting dependencies... Done The following packages were automatically installed and are no longer required: liblcms1 linux-headers-2.6.32-32-server libnspr4-0d linux-headers-2.6.32-33-server linux-headers-2.6.32-32 linux-headers-2.6.32-33 linux-headers-2.6.32-34 libcups2 tzdata-java libjpeg62 linux-headers-2.6.32-34-server libavahi-client3 ca-certificates-java libnss3-1d Use 'apt-get autoremove' to remove them. The following extra packages will be installed: linux-image-2.6.32-36-server Suggested packages: fdutils linux-doc-2.6.32 linux-source-2.6.32 linux-tools The following NEW packages will be installed: linux-image-2.6.32-36-server 0 upgraded, 1 newly installed, 0 to remove and 8 not upgraded. 3 not fully installed or removed. Need to get 0B/31.8MB of archives. After this operation, 128MB of additional disk space will be used. Do you want to continue [Y/n]? (Reading database ... 145200 files and directories currently installed.) Unpacking linux-image-2.6.32-36-server (from .../linux-image-2.6.32-36-server_2.6.32-36.79_amd64.deb) ... Done. dpkg: error processing /var/cache/apt/archives/linux-image-2.6.32-36-server_2.6.32-36.79_amd64.deb (--unpack): failed in buffer_write(fd) (10, ret=-1): backend dpkg-deb during `./boot/vmlinuz-2.6.32-36-server': No space left on device dpkg-deb: subprocess paste killed by signal (Broken pipe) Running postrm hook script /usr/sbin/update-grub. Generating grub.cfg ... Found linux image: /boot/vmlinuz-2.6.32-35-server Found linux image: /boot/vmlinuz-2.6.32-34-server Found initrd image: /boot/initrd.img-2.6.32-34-server Found linux image: /boot/vmlinuz-2.6.32-33-server Found initrd image: /boot/initrd.img-2.6.32-33-server Found linux image: /boot/vmlinuz-2.6.32-32-server Found initrd image: /boot/initrd.img-2.6.32-32-server Found linux image: /boot/vmlinuz-2.6.32-31-server Found initrd image: /boot/initrd.img-2.6.32-31-server Found linux image: /boot/vmlinuz-2.6.32-30-server Found initrd image: /boot/initrd.img-2.6.32-30-server Found memtest86+ image: /memtest86+.bin done Errors were encountered while processing: /var/cache/apt/archives/linux-image-2.6.32-36-server_2.6.32-36.79_amd64.deb E: Sub-process /usr/bin/dpkg returned an error code (1) How do I free up space on /boot so that I can fix my dependencies? Should I just delete the files manually? And then, should I resize my /boot to be larger, so this doesn't happen again? If so, how? If not, what maintenance should I be running regularly to prevent the accumulation of this cruft?

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  • Why opening Ubuntu's default wallpaper (warty-final-ubuntu.png) in Image Viewer always fails?

    - by Kush
    Everytime I try to open Ubuntu (any version, since from 8.04 with which I started) default wallpaper, named "warty-final-ubuntu.png", I get the following error. I have also reported bug for the same, more than a year ago but it is still unresolved. Also I don't get the point why the default wallpaper is still named as "warty-final-ubuntu.png" instead of having actual code name prefix to which wallpaper belongs eg. "precise-final-ubuntu.png" and so on. General Thoughts Lots of community effort goes under development of this marvelous distribution but we're still missing out to fix such silly issues, which is directly/indirectly affecting the number of new adopters.

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  • Storing User-uploaded Images

    - by Nyxynyx
    What is the usual practice for handling user uploaded photos and storing them on the database and server? For a user profile image: After receiving the image file from user, rename file to <image_id>_<username> Move image to /images/userprofile Add img filename to a table users containing their profile details like first_name, last_name, age, gender, birthday For a image for a review done by user: After receiving the image file from user, rename file to <image_id>_<review_id> Move image to /images/reviews Add img filename to a table reviews containing their profile details like review_id, review_content, user_id, score. Question 1: How should I go about storing the image filenames if the user can upload multiple photos for a particular review? Serialize? Question 2: Or have another table review_images with columns review_id, image_id, image_filename just for tracking images? Will doing a JOIN when retriving the image_filename from this table slow down performance noticeably? Question 3: Should all the images be stored in a single folder? Will there be a problem when we have 100K photos in the same folder? Is there a more efficient way to go about doing this?

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  • Python Image Library: How to combine 4 images into a 2 x 2 grid?

    - by Casey
    I have 4 directories with images for an animation. I would like to take the set of images and generate a single image with the 4 images arranged into a 2x2 grid for each frame of the animation. My code so far is: import Image fluid64 = "Fluid64_half_size/00" fluid128 = "Fluid128_half_size/00" fluid512 = "Fluid512_half_size/00" fluid1024 = "Fluid1024_half_size/00" out_image = "Fluid_all/00" for pic in range(1, 26): blank_image = Image.open("blank.jpg") if pic < 10: image_num = "0"+str(pic) else: image_num = str(pic) image64 = Image.open(fluid64+image_num+".jpg") image128 = Image.open(fluid128+image_num+".jpg") image512 = Image.open(fluid512+image_num+".jpg") image1024 = Image.open(fluid1024+image_num+".jpg") out = out_image + image_num + ".jpg" blank_image.paste(image64, (0,0)).paste(fluid128, (400,0)).paste(fluid512, (0,300)).paste(fluid1024, (400,300)).save(out) Not sure why it's not working. I'm getting the error: Traceback (most recent call last): File "C:\Users\Casey\Desktop\Image_composite.py", line 24, in <module> blank_image.paste(image64, (0,0)).paste(fluid128, (400,0)).paste(fluid512, ( ste(fluid1024, (400,300)).save(out) AttributeError: 'NoneType' object has no attribute 'paste' shell returned 1 Any help would be awesome. Thanks!

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  • JQuery identify current CSS background-image in three-state icon/button?

    - by T9b
    Hi I have three images being used to indicate an application icon state and I'm attempting to use css to do this. No problem with the original or hover states: #myDIV { background-image: url(icons/homeBlack.png); } #myDIV:hover { background-image: url(icons/homeWhite.png); } but I need to do two other things: 1) when the item is clicked it should use the third image $("#myDIV").click(function(event){ // change this button $(this).css("background-image", "url(icons/homeBlue.png)"); }); 2) if it is clicked again it should not apply the third image again because it's already applied - so it needs to check if it has been applied My questions are: 1) simply am I missing a css trick somewhere or is Jquery the best way to do this? 2) can I check which background-image is in place and how? I can't seem to find anything in JQuery that would allow me to determine which image is "currently" in place. Thanks in advance for any help.

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  • Is there any image converter through which I connect with java?

    - by Nitz
    Hey guys I had ask one question here but i don't get exactly as i want. So, now bcz of unsupported image in ImageIO, so i thought why don't I give other way to use it , by converting Unsupported images. So, is their any open-source image converter in java or is there any website or any tool , through which I can connect with my java application and then that tool or website convert my jpg image to jpg or png image and then store that image on some place. So that if their any image unsupported in ImageIO then also i can store that image by converting it. This whole process should be done automatically means user should not have to open that website or tool and convert it manually.

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