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• The easiest way to draw an image?

  - by Benno

  Assume you want to read an image file in a common file format from the hard drive, change the color of one pixel, and display the resulting image to the screen, in C++. Which (open-source) libraries would you recommend to accomplish the above with the least amount of code? Alternatively, which libraries would do the above in the most elegant way possible? A bit of background: I have been reading a lot of computer graphics literature recently, and there are lots of relatively easy, pixel-based algorithms which I'd like to implement. However, while the algorithm itself would usually be straightforward to implement, the necessary amount of frame-work to manipulate an image on a per-pixel basis and display the result stopped me from doing it.

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• How do I re-set a BMP file's resolution (DPI) indicator?

  - by Joshua Fox

  I have a BMP tagged as 299 DPI resolution. I'd like to change that to 99 DPI. Importantly, the DPI marker in a BMP has no structural meaning. An image has a certain width and height in pixels. The displaying application can show the image at any width in inches. So, the DPI is just a hint. However, I am dealing with some third-party software which behaves differently depending on this marker, so I need to re-set it. I will appreciate suggestions on how to do this programmatically (especially in Java) as well as in GUI graphics tools (e.g. Gimp).

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• How to "flick" a UIImageView?

  - by Meltemi

  I've got some UIViews that I'd like the user to be able to "flick" across the screen. They're not scroll views. They simply contain a raster image (png). Can anyone point me to some sample code, etc to help get me started? Something a little more heavyweight than "MoveMe" out there that helps detect a "flick" (vs a "nudge" or a drag and drop) and then carries the view off in the direction of the "flick"? OpenGL probably overkill. If possible I'd like to stay w/in the realm of Core Graphics/Animation.

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• Efficiently draw a grid in Windows Forms

  - by Joel

  I'm writing an implementation of Conway's Game of Life in C#. This is the code I'm using to draw the grid, it's in my panel_Paint event. g is the graphics context. for (int y = 0; y < numOfCells * cellSize; y += cellSize) { for (int x = 0; x < numOfCells * cellSize; x += cellSize) { g.DrawLine(p, x, 0, x, y + numOfCells * cellSize); g.DrawLine(p, 0, x, y + size * drawnGrid, x); } } When I run my program, it is unresponsive until it finishes drawing the grid, which takes a few seconds at numOfCells = 100 & cellSize = 10. Removing all the multiplication makes it faster, but not by very much. Is there a better/more efficient way to draw my grid? Thanks

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• Java : VolatileImage slower than BufferedImage.

  - by Norswap

  I'm making a game in java and in used BufferedImages to render content to the screen. I had performance issues on low end machines where the game is supposed to run, so I switched to VolatileImage which are normally faster. Except they actually slow the whole thing down. The images are created with GraphicsConfiguration.createCompatibleVolatileImage(...) and are drawn to the screen with Graphics.drawImage(...) (follow link to see which one specifically). They are drawn upon a Canvas using double buffering. Does someone has an idea of what is going wrong here ?

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• Looking for a mobile platform to view vector data and use it like a simple map

  - by Orchestrator

  I would like to develop or use an existing platform that will allow me to view custom vector data and use it as a map on mobile phones such as Android/IPhone (Maybe even WP7). I'm hoping that there's already a good infrastructure for what I need so I would not need to develop a whole infrastructure by myself. In Conclusion - Is there any existing platform that may answer my needs? If not, how would you guys suggest I should begin? How should I save my vector data? How could I read it? Should I view it with a graphics engine like OpenGL? Is there any chance this solution could be cross-platform? I know that it's possible since it was already done with apps like Waze. And it works the same on iOS and Android. Thanks!

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• Java SWT - dissolve (fade) from one image to the next.

  - by carillonator

  I'm pretty new to Java and SWT, hoping to have one image dissolve into the next. I have one image now in a Label (relevant code): Device dev = shell.getDisplay(); try { Image photo = new Image(dev, "photo.jpg"); } catch(Exception e) { } Label label = new Label(shell, SWT.IMAGE_JPEG); label.setImage(photo); Now I'd like photo to fade into a different image at a speed that I specify. Is this possible as set up here, or do I need to delve more into the org.eclipse.swt.graphics api? Also, this will be a slide show that may contain hundreds of photos, only ever moving forward (never back to a previous image)---considering this, is there something I explicitly need to do in order to remove the old images from memory? Thanks!!

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• Why do we need normalized coordinate system? Options

  - by jcyang

  Hi, I have problem understand following sentences in my textbook Computer Graphics with OpenGL. "To make viewing process independent of the requirements of any output device,graphic system convert object descriptions to normalized coordinates and apply the clipping routines." Why normalized coordinates could make viewing process independent of the requirements of any output devices? Isn't the projection coordinates already independent of output device?We only need to first scale and then translate the projection coordinate then we will get device coordinate. So why do we need first convert the projection coordinate to normalized coordinate first? "Clipping is usually performed in normlized coordinates.This allows us to reduce computations by first concatenating the various transformation matrices" Why clipping is usually performed in normlized coordinates? What kind of transformation concatenated? thanks. jcyang.

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• Will the Driver Support for Intel HD Graphics be Improved in 12.10?

  - by Hiranya

  I recently installed Ubuntu 12.04 on a HP Pavilion dv4 laptop. This is a core i7 machine with Intel HD graphics and also a separate nVidia VGA card. I had a lot of issues getting Ubuntu 12.04 working on this system. First there were issues booting up the live CD for installation. I worked around that by using the 'nomodeset' option. Then I continued to have similar issues after installation has completed. So I had to permanently add the nomodeset option to my GRUB boot configuration. At the moment I have a working installation but there are many issues: Ubuntu GUI is a bit flaky at times. The mouse pointer goes on and off when hovering over certain icons. Certain things doesn't get rendered properly on the screen. I can't access any of the tty consoles. Hitting Ctrl+Alt+F[1-6] gives me a blank screen. And once that happens I can't even come back to the UI by hitting Ctrl+Alt+F7. I've realized that tty consoles are actually working. I just can't see the text. If I enter a command like 'sudo reboot' into the empty screen the machine reboots. Can't get external displays (monitors, projectors etc) working. But I think this is probably because the VGA out is wired to the nVidia card which is not being used by Linux. colord program crashes every now and then triggering a popup message. So my main question is, will the support for Intel HD graphics be improved in the next release? Or will I have to keep using the nomodeset option in the new release too? Also I appreciate if anybody can shed some light on any of the issues listed above. Thanks in advance.

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• What to do about "system running in low-graphics mode"?

  - by ubuntubabe

  My Dell which was 5 years old suddenly karked it and I had the "low graphics" black screen and useless dialogue box. As I believed it was a dead graphics card I went out and bought a brand new machine. I put aside the new machine and tried again in vain to open the Dell. I eventually got to the command line via Ctrl+Alt+F1. I logged into my account from there, and simply started a series of sudo apt-get remove of various softwares that I knew were installed on my PC (software without any great consequence like Google earth, tweak, Skype etc). Lo and behold after a sudo reboot my computer was fine again! So now I have 2 computers. BUT one week after buying the other one and installing 12.04 because I love Ubuntu, the SAME PROBLEM arrived! I once again deleted Google earth, Skype, and did a sudo reboot and everything worked as before. I think there is a bug or something in 12.04 as this problem has never arisen with any other versions of Ubuntu.

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• How can I get nVidia CUDA or OpenCL working on a laptop with nVidia discrete card/Intel Integrated Graphics?

  - by PeterDC

  Background: I'm a 3D artist (as a hobby) and have recently started using Ubuntu 12.04 LTS as a dual-boot with Windows 7. It's running on my a fairly new 64-bit Toshiba laptop with an nVidia GeForce GT 540M GPU (graphics card). It also, however has Intel Integrated Graphics (which I suspect Ubuntu's been using). So, when I render my 3D scenes to images on Windows, I am able to choose between using my CPU or my nVidia GPU (faster). From the 3D application, I can set the GPU to use either CUDA or OpenCL. In Ubuntu, there's no GPU option. After doing (too much?) research on the issues with Linux and the nVidia Optimus technology, I am slightly more enlightened, but a lot more confused. I don't care one bit about the Optimus technology, as battery life is not by any means an issue for me. Here's my question: What can I do to be able to use CUDA-utilizing programs (such as Blender) on my nVidia GPU in Ubuntu? Will I need nVidia drivers? (I have heard they don't play nicely with Optimus setups on Linux.) Is there at least a way to use OpenCL on my GPU in Ubuntu?

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• Graph paper like drawing software

  - by Algorist

  Hi, I have a college assignment, where I have to draw diagrams of voronoi, delaunay, minimum spanning tree etc for the college. I want to do that in computer. I searched in google with no luck. Is there any good graph drawing software you are aware of? Thank you Bala

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• How to distort the desktop screen

  - by HaifengWang

  Hi friends, I want to change the shape of the desktop screen, so what are displayed on the desktop will be distorted at the same time. And the user can still operate the PC with the mouse on the distorted desktop(Run the applications, Open the "My Computer" and so on). I think I must get the projection matrix of the screen coordinate at first. Then transform the matrix, and map the desktop buffer image to the distorted mesh. Are there any interfaces which can modify the shape of the desktop screen in OpenGL or DirectX? Would you please give me some tip on it. Thank you very much in advance. Please refer to the picture from http://oi53.tinypic.com/bhewdx.jpg BR, Haifeng Addition1: I'm sorry! Maybe I didn't express clearly what I want to implement. What I want to implement is to modify the shape of the screen. So we can distort the shapes of all the applications which are run on Windows at the same time. For example that the window of "My Computer" will be distorted with the distortion of the desktop screen. And we can still operate the PC with mouse from the distorted desktop(Click the shortcut to run a program). Addition2: The projection matrix is just my assume. There isn't any desktop projection matrix by which the desktop surface is projected to the screen. What I want to implement is to change the shape of the desktop, as the same with mapping the desktop to an 3D mesh. But the user can still operate the OS on the distorted desktop(Click the shortcut to run a program, open the ie to surf the internet). Addition3: The shapes of all the programs run on the OS are changed with the distortion of the screen. It's realtime. The user can still operate the OS on the distorted screen as usually. Maybe we can intercept or override the GPU itself to implement the effect. I'm investigating GDI, I think I can find some clue for that. The first step is to find how to show the desktop on the screen.

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• Where to get laptop replacement parts?

  - by wai

  I am sure some of us have older laptops that still works but just one or two parts started not working very well. However, to send it back to the manufacturer for repair might not be worth the money (as some of them even charge consultation fees just to have it checked) as these old laptops are most probably well beyond warranty. Replacing these one or two parts could give your laptop a new lease of life. For example, I have a Dell Inspiron 640m which the fan recently failed. Everything else still works. I know enough to open up the laptop (after reading the service manual) and put it back together again, hence a replacement fan could save it. However, finding these parts turned out to be difficult. I guess I wouldn't be able to get it from Dell since I have been searching around the Dell forums and concluded if I were going to get Dell to at least talk to me, I would have to pay some money (since my warranty expired). I found this online:- http://www.parts-people.com/index.php?action=item&id=3725 However, as I don't live in the United States, shipping alone would cost me 3 times more than the part in question. In addition, if there's a problem, it would be difficult because I probably would have to mail the parts back (costing more money). One of my friend spilled water on her Macbook, she sent it back to Apple and they told her the cost of repairing it exceeds that of buying a new Macbook. They probably have to change everything except the LCD screen. I opened it up and found that most of the parts are still working, only the RAM had fried. Replaced it and it's working again. For some time before discovering only the RAM fried, I was toying with the idea of replacing the logic board myself but looks like I didn't have to. =) Now I know there's a site for Macbooks used replacement parts:- http://www.ifixit.com/ The question is, does anyone know where to get replacement parts at their own locality? It might benefit the community as a whole. Someone might know a local computer store that sells precisely just the things we needed (for now, I hope to find a shop that sells just the fan). If you own a laptop which you had an easy experience finding the replacement parts, do post that as well. PS: I wish laptop manufacturers have outlets where they sell these replacement parts (or at least let you place an order).

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• Where to get laptop replacement parts?

  - by wai

  I am sure some of us have older laptops that still works but just one or two parts started not working very well. However, to send it back to the manufacturer for repair might not be worth the money (as some of them even charge consultation fees just to have it checked) as these old laptops are most probably well beyond warranty. Replacing these one or two parts could give your laptop a new lease of life. For example, I have a Dell Inspiron 640m which the fan recently failed. Everything else still works. I know enough to open up the laptop (after reading the service manual) and put it back together again, hence a replacement fan could save it. However, finding these parts turned out to be difficult. I guess I wouldn't be able to get it from Dell since I have been searching around the Dell forums and concluded if I were going to get Dell to at least talk to me, I would have to pay some money (since my warranty expired). I found this online:- http://www.parts-people.com/index.php?action=item&id=3725 However, as I don't live in the United States, shipping alone would cost me 3 times more than the part in question. In addition, if there's a problem, it would be difficult because I probably would have to mail the parts back (costing more money). One of my friend spilled water on her Macbook, she sent it back to Apple and they told her the cost of repairing it exceeds that of buying a new Macbook. They probably have to change everything except the LCD screen. I opened it up and found that most of the parts are still working, only the RAM had fried. Replaced it and it's working again. For some time before discovering only the RAM fried, I was toying with the idea of replacing the logic board myself but looks like I didn't have to. =) Now I know there's a site for Macbooks used replacement parts:- http://www.ifixit.com/ The question is, does anyone know where to get replacement parts at their own locality? It might benefit the community as a whole. Someone might know a local computer store that sells precisely just the things we needed (for now, I hope to find a shop that sells just the fan). If you own a laptop which you had an easy experience finding the replacement parts, do post that as well. PS: I wish laptop manufacturers have outlets where they sell these replacement parts (or at least let you place an order).

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• Custom built machine has much higher power consumption than expected

  - by foraidt

  I built a machine according to the specs of a computer magazine (c't, Germany). According to the magazine, the power consumption should be at around 10W. I don't want to go into the specifics of the hardware but rather ask for general advice on where to look: I updated the BIOS/UEFI version to the latest version, installed all the recommended drivers and unplugged all hardware that's not necessary to boot into Windows. All that was left is the power supply, mainboard, cpu, cpu cooler and one SSD drive. But still I measured a power consumption of 50W, which is 40W more than it should be. I tried booting Linux Mint from a USB stick, so I don't think it's some Windows-related problem.. Where else could I look? Update 1 I dind't want the question to get closed for being too localized but if more details are necessary, here they are: The system is a desktop PC. The power consumption is measured using a Brennenstuhl PM 231 device, which was tested also by c't and they found it quite accurate. The PSU is an Enermax ETL300AWT, the mainboard Intel DH87RL (Socket 1150) and the CPU Intel G3220 (Haswell). Update 2 There is no online version of the article*. The most details I found can be read on its project page (in German, though...) (*)You can pay for downloadable PDFs, however. English translation of that project page Update 3 Regarding the sceptics: It may sound ridiculous but apparently 10W idle consumption is possible with Intel's Haswell architecture. As a kind of proof, there's an additional Blog article explicitly listing the steps needed to reduce the idle consumption to 10W. Additional hardware: I measured the consumption without the HDD, and as expected the usage dropped by around 10W. I have no chassis fans and the CPU fan is a "Scythe Mugen 4" model. It runs at around 600rpm so I think it won't draw much. When stripping off all my extra components I should be at 10W. But I'm not getting anywhere near that. I would be happy to see "just" 15W in the stripped down version but currently I'm not getting below 50W no matter which component I remove. As I see it this cannot be explained by the PSU being less efficient at lower consumption. I also waited half an hour or so (also checked that no Windows updates were running in the background) and the consumption dind't drop by more than a few watts.

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• Tablet as Car Computer

  - by Austin Fitzpatrick

  Okay, so forward this off to the right place if this isn't the right place to ask this question. I want to use a tablet computer as a car-computer. Minimum features would be to run my music (through iPod, Pandora, whatever I want) and GPS Navigation, watch TV or movies while I'm parked waiting for people, and the hard one: it needs to answer my phone calls with a pleasant interface much like in-dash systems do. It needs to detect that my phone is ringing in my pocket and provide an on-screen answer/ignore and then route the audio through the cars speakers. It would be nice to dial out and have address book access, but that is somewhat secondary. I have an iPhone myself and I figured that an iPad with 3G might make a good system for this - but I'm open to other options if an iPad can't do everything I need. I'm willing to write code, and I'm willing to jailbreak one or both devices. I haven't done much work in Obj-C, but I'm not opposed to learning a new language for this project. It's self enrichment for the most part, as I'm sure I can buy an indash entertainment system for less. Does anyone have experience with the iPhone/iPad SDK that can tell me whether or not it would be possible to get it an iPad to answer my calls in the car? What about an Android tablet? (that Adam looks promising, too).

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• What programming languages do the top tier Universities teach?

  - by Simucal

  I'm constantly being inundated with articles and people talking about how most of today's Universities are nothing more than Java vocational schools churning out mediocre programmer after mediocre programmer. Our very own Joel Spolsky has his famous article, "The Perils of Java Schools." Similarly, Alan Kay, a famous Computer Scientist (and SO member) has said this in the past: "I fear — as far as I can tell — that most undergraduate degrees in computer science these days are basically Java vocational training." - Alan Kay (link) If the languages being taught by the schools are considered such a contributing factor to the quality of the school's program then I'm curious what languages do the "top-tier" computer science schools teach (MIT, Carnegie Mellon, Stanford, etc)? If the average school is performing so poorly due in large part the languages (or lack of) that they teach then what languages do the supposed "good" cs programs teach that differentiate them? If you can, provide the name of the school you attended, followed by a list of the languages they use throughout their coursework. Edit: Shog-9 asks why I don't get this information directly from the schools websites themselves. I would, but many schools websites don't discuss the languages they use in their class descriptions. Quite a few will say, "using high-level languages we will...", without elaborating on which languages they use. So, we should be able to get a pretty accurate list of languages taught at various well known institutions from the various SO members who have attended at them.

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• Execute less compiler anywhere on the computer

  - by Xenioz

  I'm having a little problem with executing *.cmd files so I can execute them anywhere on the computer with cmd. What I exactly want is to execute the less.cmd file, which support optional arguments and uses lessc.wsf (Less.js compiler for Windows Script Host) for converting less css to pure css. The less.cmd contains: ::For convenience @cscript //nologo "%~dp0lessc.wsf" %* What I've done so far: added absolute path to lessc.cmd to the PATH system variable and moved .cmd in the PATHTEXT system variable to the beginning. Also did this: From a command prompt; assoc .bat should return with ..bat=batfile If not assoc .bat=batfile to restore the default file type association. ftype batfile should return with batfile="%1" %* If not ftype batfile="%1" %* to restore the default "Open" action for the file type. This still doesn't work unless I approach the cmd file with a absolute path in cmd, if I enter lessc anywhere else then I get C:\Intel Intel is not recognized as an internal or external command, operable program or batch file. , I've restarted my computer more than once to be sure changes will take effect. I hope somebody has the answer.

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• maximum memory which malloc can allocate!

  - by Vikas

  I was trying to figure out how much memory I can malloc to maximum extent on my machine (1 Gb RAM 160 Gb HD Windows platform). I read that maximum memory malloc can allocate is limited to physical memory.(on heap) Also when a program exceeds consumption of memory to a certain level, the computer stops working because other applications do not get enough memory that they require. So to confirm,I wrote a small program in C, int main(){ int *p; while(1){ p=(int *)malloc(4); if(!p)break; } } Hoping that there would be a time when memory allocation will fail and loop will be breaked. But my computer hanged as It was an infinite loop. I waited for about an hour and finally I had to forcely shut down my computer. Some questions: Does malloc allocate memory from HD also? What was the reason for above behaviour? Why didn't loop breaked at any point of time.? Why wasn't there any allocation failure?

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• Bastion - Indie Humble Bundle

  - by user68008

  I have downloaded Bastion for Ubuntu and installed in the home folder normally. When executing "Games Bastion" nothing happens. Running Bastion directly from the installation folder results in the error below Unhandled Exception: System.EntryPointNotFoundException: glProgramParameteri at (wrapper managed-to-native) OpenTK.Graphics.OpenGL.GL/Core:ProgramParameteri (uint,OpenTK.Graphics.OpenGL.AssemblyProgramParameterArb,int) at OpenTK.Graphics.OpenGL.GL.ProgramParameter (Int32 program, AssemblyProgramParameterArb pname, Int32 value) [0x00000] in <filename unknown>:0 at Microsoft.Xna.Framework.Graphics.EffectPass.ApplyPass () [0x00000] in <filename unknown>:0 at Microsoft.Xna.Framework.Graphics.Effect.DefineTechnique (System.String techniqueName, System.String passName, Int32 vertexIndex, Int32 fragmentIndex) [0x00000] in <filename unknown>:0 at Microsoft.Xna.Framework.Graphics.SpriteEffect..ctor (Microsoft.Xna.Framework.Graphics.GraphicsDevice graphicsDevice) [0x00000] in <filename unknown>:0 at Microsoft.Xna.Framework.Graphics.SpriteBatch..ctor (Microsoft.Xna.Framework.Graphics.GraphicsDevice graphicsDevice) [0x00000] in <filename unknown>:0 at GSGE.ExceptionGame.LoadContent () [0x00000] in <filename unknown>:0 <snip> I have tried some solutions on the internet, like adding OpenTK.dll.config the line below: <dllmap os="linux" dll="libXi" target="libXi.so.6"/> This didn't help. Also tried running as sudo and that didn't help. Some posts said that this might be a problem with Ubuntu noveau drivers. But I'm using the NVIDIA proprietary drivers. DISTRIB_ID=Ubuntu DISTRIB_RELEASE=10.04 DISTRIB_CODENAME=lucid DISTRIB_DESCRIPTION="Ubuntu 10.04.4 LTS" OpenGL vendor string: NVIDIA Corporation OpenGL renderer string: GeForce 9400 GT/PCI/SSE2 OpenGL version string: 3.2.0 NVIDIA 195.36.24 direct rendering: Yes

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• Reset or clear the UIView from UILabels

  - by Nicsoft

  Hello, I have created an UIView on which I have a number of labels and I'm also drawing some lines in the same UIView. Sometimes I update the lines that I'm drawing. Now, the problem I am having is that when I update the lines, they get drawn according to my wish. But the labels are overwriting themselves. This shouldn't have been a problem if it wasn't for that the position is changed about 1 pixel and that makes the text go blurry. I don't know how to remove the labels before they are redrawn. I do remove the labels from the superview and add them back when drawRect is called, but the SetNeedDisplay doesn't clear the screen before the graphic is updated, I guess (I think I read that SetNeedsDisplay/drawRect doesn't clear the screen, just updating the content. Couldn't find the text now while searching)? What is the pattern to use here, should I create a retangle with the size of the screen (or the area where the labels are) and fill it with the background colour, or is there any other way to clear or reset the UIView (I don't want to release and create the UIView again). The view is created in IB and associated with a custom UIView. In IB I add some buttons and other static labels. The above labels and graphics is created programatically. Any comments would be helpful! Thanks in advance!

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• Double buffering with C# has negative effect

  - by Roland Illig

  I have written the following simple program, which draws lines on the screen every 100 milliseconds (triggered by timer1). I noticed that the drawing flickers a bit (that is, the window is not always completely blue, but some gray shines through). So my idea was to use double-buffering. But when I did that, it made things even worse. Now the screen was almost always gray, and only occasionally did the blue color come through (demonstrated by timer2, switching the DoubleBuffered property every 2000 milliseconds). What could be an explanation for this? using System; using System.Drawing; using System.Windows.Forms; namespace WindowsFormsApplication1 { public partial class Form1 : Form { public Form1() { InitializeComponent(); } private void Form1_Paint(object sender, PaintEventArgs e) { Graphics g = CreateGraphics(); Pen pen = new Pen(Color.Blue, 1.0f); Random rnd = new Random(); for (int i = 0; i < Height; i++) g.DrawLine(pen, 0, i, Width, i); } // every 100 ms private void timer1_Tick(object sender, EventArgs e) { Invalidate(); } // every 2000 ms private void timer2_Tick(object sender, EventArgs e) { DoubleBuffered = !DoubleBuffered; this.Text = DoubleBuffered ? "yes" : "no"; } } }

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• Producing CCITT compressed TIFF from CGImage

  - by Brian Postow

  I have a CGImage (core graphics, C/C++). It's grayscale. Well, originally it was B/W, but the CGImage may be RGB. That shouldn't matter. I want to create a CCITT-Group 4 TIFF. I can create an LZW TIFF (grayscale or color) via creating a destination with the correct dictionary and adding the image in. No problem. However, there doesn't seem to be an equivalent kCGImagePropertyTIFFCompression value to represent CCITT-4. It should be 4, but that produces uncompressed. I have a manual CCITT compression routine, so if I can get the binary (1 bit per pixel) data, I'm set. But I can't seem to get 1 BPP data out of a CGImage. I have code that is supposed to put the CGImage into a CGBitmapContext and then give me the data, but it seems to be giving me all black. I've asked a couple of questions today trying to get at this, but I just figured, lets ask the question I REALLY want answered and see if someone can answer it. There's GOT to be a way to do this. I've got to be missing something dumb. What is it?

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• Defining Light Coordinates

  - by Zachary

  I took a Computer Graphics exam a couple of days ago which had extra credit question like the following: A light can be defined in one of two ways. It can be defined in world coordinates, e.g. a street light, or in the viewer (eye coordinates), e.g., a head-lamp worn by a miner. In either case the viewpoint can freely change. Describe how the light should be transformed different in these two cases. Since I won't get to see the results of this until after spring break, I thought I would ask here. It seems like the analogies being used are misleading - could you not define a light source that is located at the viewers eye in world coordinates just as well as you could in eye coordinates? I've been doing some research on how OpenGL handles light, and it seems as though it always uses eye coordinates - the ModelView matrix would be applied to any light in world coordinates. In that case the answer may just be that you would have to transform light defined in world coordinates into eye coordinates using something like the ModelView matrix, while light defined in eye coordinates would only need to be transformed by the projection matrix. Then again I could be totally under thinking (or over thinking this). Another thought I had is that it determines which way you render shadows, but that has more to do with the location of the light and its type (point, directional, emission, etc) than what coordinates it is represented in. Any ideas?

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