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• Cannot dual Windows XP and Ubuntu

  - by Fabio Machado

  I am new to Ubuntu and at the moment I am trying to get Ubuntu 12.10 to one of my machines. The machine is a Pentium 4 @ 3.06, 2Gb RAM, 200GB Hard Drive and a NVidia GeForce 8800 GT. A few days ago, I tried Ubuntu without installing and it worked perfectly. Yesterday, I decided to formatted the hard drive and divide my hard drive into four partitions: 1 for the XP, 1 for Ubuntu, 1 for swamp and 1 where I will have my documents. Everything went great, I installed XP and then Ubuntu but I did something wrong on the partition window (Ubunto partion window) that I ended up without boot loader. This morning, I formatted everything again, installed XP and when I went to install Ubuntu (with the same DVD as before) the problems started. First, I had a black screen with a msg written with white text saying something like: unable to find a medium containing a live file system. After I burned another CD and tried again, I got stuck at the red dots (loading screen). I then went online and I read somewhere that it could be the CD, so I checked the integrity of the CD and everything was fine. I also unplugged all USBs connected to the computer and nothing changed. I goggled further options to try to solve my problem and some users suggested that people having these types of problems should try the alternate installation, which if I am not wrong is for networks. I then tried to install and yes the installation process was different from the normal CD, but it did get stuck on a page where it was doing something, like: ...finding ethd0 and it was stuck on the 100%. I tried USB installation as well and it also got stuck at the red dots (I do not have USB 3.0 on the computer in question). I have burned 5 different CD's and all at low speed. I checked the integrity and all are fine. I downloaded other distribution as well as other versions of Ubuntu and I still cannot install or even run the Live CD of Ubuntu or any other distribution. What is really annoying me is that everything was working perfectly before, when I first tried to install Ubuntu. Anyway, any help is welcome. Edit: My boot load is normal, no errors and all the hardware is working fine. I forgot to mention that after the loading screen (red dots) gets stuck, the DVD drive and the hard drive goes into idle state. I also restored the default values of the BIOS and no luck.

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• File copying utility like rsync with error handling like ddrescue, for data recovery from a hard drive with bad sectors or hardware failure

  - by purefusion

  I have a hard drive with either bad blocks or sectors that are failing to read due to potential mechanical issues, such as a bad disk head, bad motor, or some other issue that is causing the hard drive to read data excruciatingly slowly and with lots of read errors. I'm seeing an average of 50 KB/sec, with some reads dropping below 10 KB/sec, and frequently it gets stuck on a file or sector altogether, usually for quite a long time—from 2-10 minutes or more (when using rsync, before it times out). Speed seems to vary wildly, and it gets stuck on files a lot, and when it finally gets "unstuck" it only seems to last for a short burst before it gets stuck again. The drive is also very quiet with only an occasional sound of files copying (usually when it gets stuck/unstuck for a brief time, before getting stuck again). Thus, there are none of those evil sounds that are normally associated with HDD death. Someone suggested that the problems sounded like they might be caused by a misaligned disk head, which requires a lot of re-reads before it finally reads data with success. Sounds plausible, but I digress... Anyway, the problem with rsync is that it seems to have no decent error handling support. Obviously, it wasn't meant for use in recovering data from failing hard drives, but all the so-called "data recovery" utilities out there that are meant for such use usually focus on recovery of deleted files or messed up partitions, rather than copying files off dying hard drives. Deleted file recovery is not what I need, obviously, so perhaps you can understand my disappointment in not being able to find what I'm after yet. Naturally, this is where you'd probably say "You should use ddrescue!" Well, that's all fine and dandy, but I've already got most of the data backed up, so I just want to recover certain files. I'm not concerned with trying to recover a full partition block-by-block as ddrescue does. I am only interested in rescuing just specific files and directories. Ideally, what I'd like is some sort of cross between rsync and ddrescue: something that lets me specify source and destination as directories of normal files like rsync (rather than two full partitions as ddrescue requires), with a way to skip files with errors in an initial run, and then allows me to attempt recovery of those files with errors in a later run (with a slightly altered command, of course), perhaps even offering an option to specify the number of retry attempts ...just like how ddrescue works with blocks, only I want a utility that works with specific files/directories like rsync does. So am I daydreaming here, or does something out there exist that can do this? Or, maybe even a way to make rsync or ddrescue work in such a way? I'm really open to whatever solutions might work, so long as they let me choose which files I want to "rescue", and can skip files with errors in the initial run, and try/retry those errors again later. So far I've tried rsync with the following options, but it often gets stuck on a file for longer than the timeout, and ideally I'd just like it to move on to the next file and come back later to the files it gets stuck on. I don't think that's possible though. Anyway, here's what I've been using up till now: rsync -avP --stats --block-size=512 --timeout=600 /path/to/source/* /path/to/destination/

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• Ubuntu 12.04 suddenly will not boot after compiz crash on lockscreen

  - by schonjones

  Yesterday i went to work and closed my laptop. When i got home I couldn't get the lock screen to come back up. ctrl+alt+f2 to get to a terminal and Tried to kill compiz, compiz was not running so I tried to restart it got an error opening the display so i tried to restart lightdm again couldn't open display. so I restarted and now I am stuck on the loading screen. I tried booting in recovery mode and all options hang except root, but i'm stuck with read only. booting from a live cd I can mount the drive but again stuck with read only. I'm completely stuck here. checking my default-display-manager returns "/usr/sbin/elsa" as the only line and can't edit it. I've got an 11.10 live cd and my /home is encrypted so i can't try to back anything up at the moment either. How can i resolve this or at the least back up some of my data? Please help!

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• Hybrid Graphics on Ubuntu 12.04 switching to discrete

  - by cfstras

  I have a Sony Vaio VPCCB-27FX with hybrid graphics. Using vgaswitcheroo enables me to switch my discrete card off to save power. Now when i want to switch to the discrete card for performance, my system freezes. I already tried logging out and killing x with service lightdm stop, but still, it freezes as soon as I echo DIS > switch. typing blindly, echo IGD > switch returns me to my console where it reads [ 179.555171] i915: switched off, but it seems the discrete card never gets switched on... running echo DDIS > switch gives me the following: [540....] [drm:atop_op_jump] *ERROR* atombios stuck in loop for more than 5secs aborting [540....] [drm:atom_execute_table_locked] *ERROR* atombios stuck executing CEE2 (len 62, WS 0, PS 0) @ 0xCEFE [540....] [drm:atom_execute_table_locked] *ERROR* atombios stuck executing BBF6 (len 1036, WS 4, PS 0) @ 0xBCF3 [540....] [drm:atom_execute_table_locked] *ERROR* atombios stuck executing BB8C (len 76, WS 0, PS 0) @ 0xBB94 [541....] [drm:r600_RING_TEST] *ERROR* radeon: ring test failed (scratch(0x8504)=0xFFFFFFFF) [541....] [drm:evergreen_resume] *ERROR* evergreen startup failed on resume after that, the atombios part repeats a few times. also, the terminal locks up again and sysrq+REISUB is my only rescue. Has anybody an idea how I can switch to my discrete card without the system locking up? #uname -srvmpio Linux 3.2.0-24-generic #39-Ubuntu SMP Mon May 21 16:52:17 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux #lsb_release -r Description: Ubuntu 12.04 LTS

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• How to Stich to Image objects in Java

  - by Imran

  Hi, I have a scenario in which i`m getting a number of tiles (e.g.12) from my mapping server. Now for buffering and offline functions I need to join them all back again so that we have to deal with 1 single image object instead of 12. I ve tried to do it without JAI my code is below. package imagemerge; import java.awt.*; import java.awt.image.*; import java.awt.event.*; public class ImageSticher extends WindowAdapter { Image tile1; Image tile2; Image result; ColorModel colorModel; int width,height,widthr,heightr; //int t1,t2; int t12[]; public ImageSticher() { } public ImageSticher (Image img1,Image img2,int w,int h) { tile1=img1; tile2=img2; width=w; height=h; colorModel=ColorModel.getRGBdefault(); } public Image horizontalStich() throws Exception { widthr=width*2; heightr=height; t12=new int[widthr * heightr]; int t1[]=new int[width*height]; PixelGrabber p1 =new PixelGrabber(tile1, 0, 0, width, height, t1, 0, width); p1.grabPixels(); int t2[]=new int[width*height]; PixelGrabber p2 =new PixelGrabber(tile2, 0, 0, width, height, t1, 0, width); p2.grabPixels(); int y, x, rp, rpi; int red1, red2, redr; int green1, green2, greenr; int blue1, blue2, bluer; int alpha1, alpha2, alphar; for(y=0;y<heightr;y++) { for(x=0;x<widthr;x++) { //System.out.println(x); rpi=y*widthr+x; // index of resulting pixel; rp=0; //initializing resulting pixel System.out.println(rpi); if(x<(widthr/2)) // x is less than width , copy first tile { //System.out.println("tile1="+x); blue1 = t1[rpi] & 0x00ff; // ERROR occurs here green1=(t1[rpi] >> 8) & 0x00ff; red1=(t1[rpi] >> 16) & 0x00ff; alpha1 = (t1[rpi] >> 24) & 0x00ff; redr = (int)(red1 * 1.0); // copying red band pixel into redresult,,,,1.0 is the alpha valye redr = (redr < 0)?(0):((redr>255)?(255):(redr)); greenr = (int)(green1 * 1.0); // redr = (int)(red1 * 1.0); // greenr = (greenr < 0)?(0):((greenr>255)?(255):(greenr)); bluer = (int)(blue1 * 1.0); bluer = (bluer < 0)?(0):((bluer>255)?(255):(bluer)); alphar = 255; //resulting pixel computed rp = (((((alphar << 8) + (redr & 0x0ff)) << 8) + (greenr & 0x0ff)) << 8) + (bluer & 0x0ff); } else // index is ahead of half way...copy second tile { blue2 = t2[rpi] & 0x00ff; // blue band bit of first tile green2=(t2[rpi] >> 8) & 0x00ff; red2=(t2[rpi] >> 16) & 0x00ff; alpha2 = (t2[rpi] >> 24) & 0x00ff; redr = (int)(red2 * 1.0); // copying red band pixel into redresult,,,,1.0 is the alpha valye redr = (redr < 0)?(0):((redr>255)?(255):(redr)); greenr = (int)(green2 * 1.0); // redr = (int)(red2 * 1.0); // greenr = (greenr < 0)?(0):((greenr>255)?(255):(greenr)); bluer = (int)(blue2 * 1.0); bluer = (bluer < 0)?(0):((bluer>255)?(255):(bluer)); alphar = 255; //resulting pixel computed rp = (((((alphar << 8) + (redr & 0x0ff)) << 8) + (greenr & 0x0ff)) << 8) + (bluer & 0x0ff); } t12[rpi] = rp; // copying resulting pixel in the result int array which will be converted to image } } MemoryImageSource mis; if (t12!=null) { mis = new MemoryImageSource(widthr, heightr, colorModel, t12, 0, widthr); result = Toolkit.getDefaultToolkit().createImage(mis); return result; } return null; } } now to check the my theory Im trying to join or stich two tiles horizontaly but im getting the error : java.lang.ArrayIndexOutOfBoundsException: 90000 at imagemerge.ImageSticher.horizontalStich(ImageSticher.java:69) at imageStream.ImageStream.getImage(ImageStream.java:75) at imageStream.ImageStream.main(ImageStream.java:28) is there some kind of limitation because when stiching two images of 300 x 300 horizontally it means the resulting image will be 600 x 300 ... that would make 180000 index size but its giving error at 90000, what am I doing wrong here

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• What is the significance of these different width, height and resolution parameters?

  - by ??????? ???????????

  An image with a pixel resolution of 640 x 480 has additional dimension and resolution parameters according to exiftool. I'm unsure what they mean. Why are the X / Y Resolution parameters the same?Should they not reflect the pixel dimensions of the image? What does Exif Image Size mean and how is it different from the pixel dimensions? What is the focal plane? Does it have any relation to the device used to capture this image? $ exiftool evil1.jpg | egrep 'Width|Height|Resolution' X Resolution : 180 Y Resolution : 180 Resolution Unit : inches Exif Image Width : 400 Exif Image Height : 300 Focal Plane X Resolution : 8114.285714 Focal Plane Y Resolution : 8114.285714 Focal Plane Resolution Unit : inches Image Width : 640 Image Height : 480 If needed, the original image can be obtained from: here=http://www.pythonchallenge.com/pc/return/evil1.jpg wget --user=huge --password=file $here

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• image processing algorithm in MATLAB

  - by user261002

  I am trying to reconstruct an algorithm belong to this paper: Decomposition of biospeckle images in temporary spectral bands Here is an explanation of the algorithm: We recorded a sequence of N successive speckle images with a sampling frequency fs. In this way it was possible to observe how a pixel evolves through the N images. That evolution can be treated as a time series and can be processed in the following way: Each signal corresponding to the evolution of every pixel was used as input to a bank of filters. The intensity values were previously divided by their temporal mean value to minimize local differences in reflectivity or illumination of the object. The maximum frequency that can be adequately analyzed is determined by the sampling theorem and s half of sampling frequency fs. The latter is set by the CCD camera, the size of the image, and the frame grabber. The bank of filters is outlined in Fig. 1. In our case, ten 5° order Butterworth11 filters were used, but this number can be varied according to the required discrimination. The bank was implemented in a computer using MATLAB software. We chose the Butter-worth filter because, in addition to its simplicity, it is maximally flat. Other filters, an infinite impulse response, or a finite impulse response could be used. By means of this bank of filters, ten corresponding signals of each filter of each temporary pixel evolution were obtained as output. Average energy Eb in each signal was then calculated: where pb(n) is the intensity of the filtered pixel in the nth image for filter b divided by its mean value and N is the total number of images. In this way, en values of energy for each pixel were obtained, each of hem belonging to one of the frequency bands in Fig. 1. With these values it is possible to build ten images of the active object, each one of which shows how much energy of time-varying speckle there is in a certain frequency band. False color assignment to the gray levels in the results would help in discrimination. and here is my MATLAB code base on that : clear all for i=0:39 str = num2str(i); str1 = strcat(str,'.mat'); load(str1); D{i+1}=A; end new_max = max(max(A)); new_min = min(min(A)); for i=20:180 for j=20:140 ts = []; for k=1:40 ts = [ts D{k}(i,j)]; %%% kth image pixel i,j --- ts is time series end ts = double(ts); temp = mean(ts); ts = ts-temp; ts = ts/temp; N = 5; % filter order W = [0.00001 0.05;0.05 0.1;0.1 0.15;0.15 0.20;0.20 0.25;0.25 0.30;0.30 0.35;0.35 0.40;0.40 0.45;0.45 0.50]; N1 = 5; for ind = 1:10 Wn = W(ind,:); [B,A] = butter(N1,Wn); ts_f(ind,:) = filter(B,A,ts); end for ind=1:10 imag_test1{ind}(i,j) =sum((ts_f(ind,:)./mean(ts_f(ind,:))).^2); end end end for i=1:10 temp_imag = imag_test1{i}(:,:); x=isnan(temp_imag); temp_imag(x)=0; temp_imag=medfilt2(temp_imag); t_max = max(max(temp_imag)); t_min = min(min(temp_imag)); temp_imag = (temp_imag-t_min).*(double(new_max-new_min)/double(t_max-t_min))+double(new_min); imag_test2{i}(:,:) = temp_imag; end for i=1:10 A=imag_test2{i}(:,:); B=A/max(max(A)); B=histeq(B); figure,imshow(B) colorbar end but I am not getting the same result as paper. has anybody has aby idea why? or where I have gone wrong? Refrence Link to the paper

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• Fastest way to read data from a lot of ASCII files

  - by Alsenes

  Hi guys, for a college exercise that I've already submitted I needed to read a .txt file wich contained a lot of names of images(1 in each line). Then I needed to open each image as an ascii file, and read their data(images where in ppm format), and do a series of things with them. The things is, I noticed my program was taking 70% of the time in the reading the data from the file part, instead of in the other calculations that I was doing (finding number of repetitions of each pixel with a hash table, finding diferents pixels beetween 2 images etc..), which I found quite odd to say the least. This is how the ppm format looks like: P3 //This value can be ignored when reading the file, because all image will be correctly formatted 4 4 255 //This value can be also ignored, will be always 255. 0 0 0 0 0 0 0 0 0 15 0 15 0 0 0 0 15 7 0 0 0 0 0 0 0 0 0 0 0 0 0 15 7 0 0 0 15 0 15 0 0 0 0 0 0 0 0 0 This is how I was reading the data from the files: ifstream fdatos; fdatos.open(argv[1]); //Open file with the name of all the images const int size = 128; char file[size]; //Where I'll get the image name Image *img; while (fdatos >> file) { //While there's still images anmes left, continue ifstream fimagen; fimagen.open(file); //Open image file img = new Image(fimagen); //Create new image object with it's data file ……… //Rest of the calculations whith that image ……… delete img; //Delete image object after done fimagen.close(); //Close image file after done } fdatos.close(); And inside the image object read the data like this: const int tallafirma = 100; char firma[tallafirma]; fich_in >> std::setw(100) >> firma; // Read the P3 part, can be ignored int maxvalue, numpixels; fich_in >> height >> width >> maxvalue; // Read the next three values numpixels = height*width; datos = new Pixel[numpixels]; int r,g,b; //Don't need to be ints, max value is 256, so an unsigned char would be ok. for (int i=0; i<numpixels; i++) { fich_in >> r >> g >> b; datos[i] = Pixel( r, g ,b); } //This last part is the slow one, //I thing I should be able to read all this data in one single read //to buffer or something which would be stored in an array of unsigned chars, //and then I'd only need to to do: //buffer[0] -> //Pixel 1 - Red data //buffer[1] -> //Pixel 1 - Green data //buffer[2] -> //Pixel 1 - Blue data So, any Ideas? I think I can improve it quite a bit reading all to an array in one single call, I just don't know how that is done. Also, is it posible to know how many images will be in the "index file"? Is it posiible to know the number of lines a file has?(because there's one file name per line..) Thanks!!

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• Drawing outlines around organic shapes

  - by ThunderChunky_SF

  One thing that seems particularly easy to do in the Flash IDE but difficult to do with code is to outline an organic shape. In the IDE you can just use the inkbucket tool to draw a stroke around something. Using nothing but code it seems much trickier. One method I've seen is to add a glow filter to the shape in question and just mess with the strength. But what if i want to only show the outline? What I'd like to do is to collect all of the points that make up the edge of the shape and then just connect the dots. I've actually gotten so far as to collect all of the points with a quick and dirty edge detection script that I wrote. So now I have a Vector of all the points that makeup my shape. How do I connect them in the proper sequence so it actually looks like the original object? For anyone who is interested here is my edge detection script: // Create a new sprite which we'll use for our outline var sp:Sprite = new Sprite(); var radius:int = 50; sp.graphics.beginFill(0x00FF00, 1); sp.graphics.drawCircle(0, 0, radius); sp.graphics.endFill(); sp.x = stage.stageWidth / 2; sp.y = stage.stageHeight / 2; // Create a bitmap data object to draw our vector data var bmd:BitmapData = new BitmapData(sp.width, sp.height, true, 0); // Use a transform matrix to translate the drawn clip so that none of its // pixels reside in negative space. The draw method will only draw starting // at 0,0 var mat:Matrix = new Matrix(1, 0, 0, 1, radius, radius); bmd.draw(sp, mat); // Pass the bitmap data to an actual bitmap var bmp:Bitmap = new Bitmap(bmd); // Add the bitmap to the stage addChild(bmp); // Grab all of the pixel data from the bitmap data object var pixels:Vector.<uint> = bmd.getVector(bmd.rect); // Setup a vector to hold our stroke points var points:Vector.<Point> = new Vector.<Point>; // Loop through all of the pixels of the bitmap data object and // create a point instance for each pixel location that isn't // transparent. var l:int = pixels.length; for(var i:int = 0; i < l; ++i) { // Check to see if the pixel is transparent if(pixels[i] != 0) { var pt:Point; // Check to see if the pixel is on the first or last // row. We'll grab everything from these rows to close the outline if(i <= bmp.width || i >= (bmp.width * bmp.height) - bmp.width) { pt = new Point(); pt.x = int(i % bmp.width); pt.y = int(i / bmp.width); points.push(pt); continue; } // Check to see if the current pixel is on either extreme edge if(int(i % bmp.width) == 0 || int(i % bmp.width) == bmp.width - 1) { pt = new Point(); pt.x = int(i % bmp.width); pt.y = int(i / bmp.width); points.push(pt); continue; } // Check to see if the previous or next pixel are transparent, // if so save the current one. if(i > 0 && i < bmp.width * bmp.height) { if(pixels[i - 1] == 0 || pixels[i + 1] == 0) { pt = new Point(); pt.x = int(i % bmp.width); pt.y = int(i / bmp.width); points.push(pt); } } } }

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• Are there any font rendering libraries for games development that support hinting?

  - by Richard Fabian

  I've used angel code's bitmap font generator quite a bit and though it's very good, I wondered if there would be a way of using the hinting information to provide a better readable result by using hinting to provide differing thickness based on size/pixel coverage. I imagine any solution would have to use the distance field tech presented in the valve paper on smoothing fonts while maintaining or reducing asset size. (http://www.gamedev.net/community/forums/topic.asp?topic_id=494612) but I haven't found any demos of it being used with hinting information turned on or included in the field gradients in any way. Another way of looking at this is whether there are any font bitmap generators that will output mipmaps that still maintain their readability in the face of pixel size. I think the lower mip levels would try to guarantee fill and space where it is necessary to maintain readability/topology over maintaining style/form (the point of hinting). In response to "Is there a reason you can't just render the size you want", the problem lies in the fact that font rasterisers currently don't render in 3D, and hinting information would be important in different amounts due to the pixel density being different along different axes, even differing in importance along the length of a string due to the size reducing over distance. For example, I only want horizontal hinting in a texture that is viewed from the side, and only really want vertical hinting in a font that is viewed from below or above. This isn't meant to be a renderer that tries to render a perfect outline as accurately as possible, as hinting distorts the reality of the font, instead this is meant to be a rendering solution for quite static scenes, but scenes that have 3D transformed and warped text layout. In this case the legibility is important, more important than the accuracy of representation of the polygon shape.

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• How do graphics programmers deal with rendering vertices that don't change the image?

  - by canisrufus

  So, the title is a little awkward. I'll give some background, and then ask my question. Background: I work as a web GIS application developer, but in my spare time I've been playing with map rendering and improving data interchange formats. I work only in 2D space. One interesting issue I've encountered is that when you're rendering a polygon at a small scale (zoomed way out), many of the vertices are redundant. An extreme case would be that you have a polygon with 500,000 vertices that only takes up a single pixel. If you're sending this data to the browser, it would make sense to omit ~499,999 of those vertices. One way we achieve that is by rendering an image on a server and and sending it as a PNG: voila, it's a point. Sometimes, though, we want data sent to the browser where it can be rendered with SVG (or canvas, or webgl) so that it can be interactive. The problem: It turns out that, using modern geographic data sets, it's very easy to overload SVG's rendering abilities. In an effort to cope with those limitations, I'm trying to figure out how to visually losslessly reduce a data set for a given scale and map extent (and, if necessary, for a known map pixel width and height). I got a great reduction in data size just using the Douglas-Peucker algorithm, and I believe I was able to get it to keep the polygons true to within one pixel. Unfortunately, Douglas-Peucker doesn't preserve topology, so it changed how borders between polygons got rendered. I couldn't readily find other algorithms to try out and adapt to the purpose, but I don't have much CS/algorithm background and might not recognize them if I saw them.

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• How to Detect Sprites in a SpriteSheet?

  - by IAE

  I'm currently writing a Sprite Sheet Unpacker such as Alferds Spritesheet Unpacker. Now, before this is sent to gamedev, this isn't necessarily about games. I would like to know how to detect a sprite within a spriitesheet, or more abstactly, a shape inside of an image. Given this sprite sheet: I want to detect and extract all individual sprites. I've followed the algorithm detailed in Alferd's Blog Post which goes like: Determine predominant color and dub it the BackgroundColor Iterate over each pixel and check ColorAtXY == BackgroundColor If false, we've found a sprite. Keep going right until we find a BackgroundColor again, backtrack one, go down and repeat until a BackgroundColor is reached. Create a box from location to ending location. Repeat this until all sprites are boxed up. Combined overlapping boxes (or within a very short distance) The resulting non-overlapping boxes should contain the sprite. This implementation is fine, especially for small sprite sheets. However, I find the performance too poor for larger sprite sheets and I would like to know what algorithms or techniques can be leveraged to increase the finding of sprites. A second implementation I considered, but have not tested yet, is to find the first pixel, then use a backtracking algorithm to find every connected pixel. This should find a contiguous sprite (breaks down if the sprite is something like an explosion where particles are no longer part of the main sprite). The cool thing is that I can immediately remove a detected sprite from the sprite sheet. Any other suggestions?

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• Orthographic unit translation mismatch on grid (e.g. 64 pixels translates incorrectly)

  - by Justin Van Horne

  I am looking for some insight into a small problem with unit translations on a grid. Setup 512x448 window 64x64 grid gl_Position = projection * world * position; projection is defined by ortho(-w/2.0f, w/2.0f, -h/2.0f, h/2.0f); This is a textbook orthogonal projection function. world is defined by a fixed camera position at (0, 0) position is defined by the sprite's position. Problem In the screenshot below (1:1 scaling) the grid spacing is 64x64 and I am drawing the unit at (64, 64), however the unit draws roughly ~10px in the wrong position. I've tried uniform window dimensions to prevent any distortion on the pixel size, but now I am a bit lost in the proper way in providing a 1:1 pixel-to-world-unit projection. Anyhow, here are some quick images to aide in the problem. I decided to super-impose a bunch of the sprites at what the engine believes is 64x offsets. When this seemed off place, I went about and did the base case of 1 unit. Which seemed to line up as expected. The yellow shows a 1px difference in the movement. Vertices It would appear that the vertices going into the vertex shader are correct. For example, in reference to the first image the data looks like this in the VBO: x y x y ---------------------------- tl | 0.0 24.0 64.0 24.0 bl | 0.0 0.0 -> 64.0 0.0 tr | 16.0 0.0 80.0 0.0 br | 16.0 24.0 80.0 24.0 With that said, all I am left to believe is that I am munging up my actual projection. So, I am looking for any insight into maintaining the 1:1 pixel-to-world-unit projection.

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• Collision with half semi-circle

  - by heitortsergent

  I am trying to port a game I made using Flash/AS3, to the Windows Phone using C#/XNA 4.0. You can see it here: http://goo.gl/gzFiE In the flash version I used a pixel-perfect collision between meteors (it's a rectangle, and usually rotated) that spawn outside the screen, and move towards the center, and a shield in the center of the screen(which is half of a semi-circle, also rotated by the player), which made the meteor bounce back in the opposite direction it came from, when they collided. My goal now is to make the meteors bounce in different angles, depending on the position it collides with the shield (much like Pong, hitting the borders causes a change in the ball's angle). So, these are the 3 options I thought of: -Pixel-perfect collision (microsoft has a sample(http://create.msdn.com/en-US/education/catalog/tutorial/collision_2d_perpixel_transformed)) , but then I wouldn't know how to change the meteor angle after the collision -3 BoundingCircle's to represent the half semi-circle shield, but then I would have to somehow move them as I rotate the shield. -Farseer Physics. I could make a shape composed of 3 lines, and use that as the collision object for the shield. Is there any other way besides those? Which would be the best way to do it(it's aimed towards mobile devices, so pixel-perfect is probably not a good choice)? Most of the time there's always a easier/better way than what we think of...

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• Best way to mask 2D sprites in XNA?

  - by electroflame

  I currently am trying to mask some sprites. Rather than explaining it in words, I've made up some example pictures: The area to mask (in white) Now, the red sprite that needs to be cropped. The final result. Now, I'm aware that in XNA you can do two things to accomplish this: Use the Stencil Buffer. Use a Pixel Shader. I have tried to do a pixel shader, which essentially did this: float4 main(float2 texCoord : TEXCOORD0) : COLOR0 { float4 tex = tex2D(BaseTexture, texCoord); float4 bitMask = tex2D(MaskTexture, texCoord); if (bitMask.a > 0) { return float4(tex.r, tex.g, tex.b, tex.a); } else { return float4(0, 0, 0, 0); } } This seems to crop the images (albeit, not correct once the image starts to move), but my problem is that the images are constantly moving (they aren't static), so this cropping needs to be dynamic. Is there a way I could alter the shader code to take into account it's position? Alternatively, I've read about using the Stencil Buffer, but most of the samples seem to hinge on using a rendertarget, which I really don't want to do. (I'm already using 3 or 4 for the rest of the game, and adding another one on top of it seems overkill) The only tutorial I've found that doesn't use Rendertargets is one from Shawn Hargreaves' blog over here. The issue with that one, though is that it's for XNA 3.1, and doesn't seem to translate well to XNA 4.0. It seems to me that the pixel shader is the way to go, but I'm unsure of how to get the positioning correct. I believe I would have to change my onscreen coordinates (something like 500, 500) to be between 0 and 1 for the shader coordinates. My only problem is trying to work out how to correctly use the transformed coordinates. Thanks in advance for any help!

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• Confusion with floats converted into ints during collision detection

  - by TheBroodian

  So in designing a 2D platformer, I decided that I should be using a Vector2 to track the world location of my world objects to retain some sub-pixel precision for slow-moving objects and other such subtle nuances, yet representing their bodies with Rectangles, because as far as collision detection and resolution is concerned, I don't need sub-pixel precision. I thought that the following line of thought would work smoothly... Vector2 wrldLocation; Point WorldLocation; Rectangle collisionRectangle; public void Update(GameTime gameTime) { Vector2 moveAmount = velocity * (float)gameTime.ElapsedGameTime.TotalSeconds wrldLocation += moveAmount; WorldLocation = new Point((int)wrldLocation.X, (int)wrldLocation.Y); collisionRectangle = new Rectangle(WorldLocation.X, WorldLocation.Y, genericWidth, genericHeight); } and I guess in theory it sort of works, until I try to use it in conjunction with my collision detection, which works by using Rectangle.Offset() to project where collisionRectangle would supposedly end up after applying moveAmount to it, and if a collision is found, finding the intersection and subtracting the difference between the two intersecting sides to the given moveAmount, which would theoretically give a corrected moveAmount to apply to the object's world location that would prevent it from passing through walls and such. The issue here is that Rectangle.Offset() only accepts ints, and so I'm not really receiving an accurate adjustment to moveAmount for a Vector2. If I leave out wrldLocation from my previous example, and just use WorldLocation to keep track of my object's location, everything works smoothly, but then obviously if my object is being given velocities less than 1 pixel per update, then the velocity value may as well be 0, which I feel further down the line I may regret. Does anybody have any suggestions about how I might go about resolving this?

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• Collision with half of a semi-circle

  - by heitortsergent

  I am trying to port a game I made using Flash/AS3, to the Windows Phone using C#/XNA 4.0. You can see it here: http://goo.gl/gzFiE In the flash version I used a pixel-perfect collision between meteors (it's a rectangle, and usually rotated) that spawn outside the screen, and move towards the center, and a shield in the center of the screen(which is half of a semi-circle, also rotated by the player), which made the meteor bounce back in the opposite direction it came from, when they collided. My goal now is to make the meteors bounce in different angles, depending on the position it collides with the shield (much like Pong, hitting the borders causes a change in the ball's angle). So, these are the 3 options I thought of: Pixel-perfect collision (Microsoft has a sample) , but then I wouldn't know how to change the meteor angle after the collision 3 BoundingCircle's to represent the half semi-circle shield, but then I would have to somehow move them as I rotate the shield. Farseer Physics. I could make a shape composed of 3 lines, and use that as the collision object for the shield. Is there any other way besides those? Which would be the best way to do it(it's aimed towards mobile devices, so pixel-perfect is probably not a good choice)? Most of the time there's always a easier/better way than what we think of...

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• How to Create a Grid for a 2D Game?

  - by SoulBeaver

  So I'm currently writing the engine for my videogame. I've almost integrated Tiled (I think) so I should have a map-creator here soon. My question is, how do I actually make the grid? I'm really confused here. If I create a large map with, say, 20x20 grids the size of 32x32 (screen size 640x640), then what do I do with it? Let's say I have the code for creating a window, and then place a player sprite that I can move with input, that's fine. If I use one map that's as big as the screen, then every pixel on the map is also a pixel on the game screen. The mapping is exact. Now what happens if I have a 2000x2000 map, for example? My character would have to keep moving and move the map around (or rather the camera focused on the player moves). Then I can no longer say that the screen maps exactly to the pixel position of the map. I tried making a Grid class that maps out the screen area to 32x32 tiles, but I'm not sure if that makes any sense. Once the map moves each tile would have to update its information, or something. I'm just really confused here. How do I actually make the tiles and a grid and map them to the data I get from tiled, or that I make myself? Are there any good examples of source code that I could look at?

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• My Windows 7 computer is stuck in a refresh rate not supported by my display. How can I fix this?

  - by Tim Keating

  Star Wars: The Old Republic apparently decided that my screen res should be 1680x1050 at 75hz. I have an older monitor that doesn't support that refresh rate. I fixed this problem within the game, but subsequently I alt-tabbed out of the game to the desktop & it reset me to those settings. Now my monitor shows a blank screen with "out of range" in Windows, and these settings persist even through a reboot. I booted into safe mode, but of course while there, I can only change the settings for the default driver. How can I get my machine back into a usable state?

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• Initialize preferences from XML in main Activity

  - by pixel

  My problem is that when I start application and user didn't open my PreferenceActivity so when I retrieve them don't get any default values defined in my preference.xml file. preference.xml file: <?xml version="1.0" encoding="utf-8"?> <PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android" android:key="applicationPreference" android:title="@string/config" > <ListPreference android:key="pref1" android:defaultValue="default" android:title="Title" android:summary="Summary" android:entries="@array/entry_names" android:entryValues="@array/entry_values" android:dialogTitle="@string/dialog_title" /> </PreferenceScreen> Snippet from my main Activity (onCreate method): SharedPreferences appPreferences = PreferenceManager.getDefaultSharedPreferences(this); String pref1 = appPreferences.getString("pref1", null); In result I end up with a null value.

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• How to toggle orientation lock in android?

  - by pixel

  I want to create checkbox in my preference Activity that allows user to toggle orientation change. In similar questions people write only about complete orientation lock (by overriding onConfigurationChanged method or adding configChanges in AndroidManifest.xml) or orientation enforcing ( by setRequestedOrientation ). Is there a way to toggle orientation lock?

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• How to manage orientation lock in android?

  - by pixel

  I want to create checkbox in my preference Activity that allows user to toggle orientation change. In similar questions people write only about complete orientation lock (by overriding onConfigurationChanged method or adding configChanges in AndroidManifest.xml) or orientation enforcing ( by setRequestedOrientation ). Is there a way to toggle orientation lock?

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• Cannot install 14.04 on Dell Inspiron 5447 14

  - by user292121

  I install Ubuntu version 14.04 by use USB stick is a boot devices on DELL Inspiron 5447 14" but it stuck in ubuntu logo. I change to use Linux Mint and it still stuck in the same process is pending in Mint logo. When I change to Linux Mint Compatibility Mode it shown some error meassage. For the stuck screen please see the url below: http://www.image-share.com/upload/2583/266.jpg For the error massage when I try to use Linux Mint can see as below: http://www.image-share.com/ijpg-2583-268.html How can i do next ?

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• Favourite Kohana Tips & Features?

  - by The Pixel Developer

  Inspired from the other community wiki's, I'm interested in hearing about the lesser known Kohana tips, tricks and features. Please, include only one tip per answer. Add Kohana versions if necessary. This a community wiki.

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• Video playback on VideoView disappears after going back from another Activity

  - by pixel

  I have two Activities: one with VideoView and the second one. I start watching a video in the first Activity, then during playback I start second Activity. After going back to first Activity I can hear sound but see no picture. My Video Layout: <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent"> <VideoView android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_weight="1" android:id="@+id/videoView" android:layout_gravity="center" /> <ListView android:layout_width="fill_parent" android:layout_height="125dp" android:id="@+id/ListView" /> </LinearLayout> Do you have any ideas why video doesn't appear?

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