We Keep Coding

How to capture screenshot from full screen 3D games in C# [duplicate]

Suppose I have an OpenGL game running full screen (Left 4 Dead 2). I'd like to programmatically get a screen grab of it and then write it to a video file.
I've tried GDI, D3D, and OpenGL methods (eg glReadPixels) and either receive a blank screen or flickering in the capture stream.
Any ideas?
For what it's worth, a canonical example of something similar to what I'm trying to achieve is Fraps.

There are a few approaches to this problem. Most of them are icky, and it totally depends on what kind of graphics API you want to target, and which functions the target application uses.
Most DirectX, GDI+ and OpenGL applications are double or tripple-buffered, so they all call:
void SwapBuffers(HDC hdc)
at some point. They also generate WM_PAINT messages in their message queue whenever the window should be drawn. This gives you two options.
You can install a global hook or thread-local hook into the target process and capture WM_PAINT messages. This allows you to copy the contents from the device context just before the painting happens. The process can be found by enumerating all the processes on the system and look for a known window name, or a known module handle.
You can inject code into the target process's local copy of SwapBuffers. On Linux this would be easy to do via the LD_PRELOAD environmental variable, or by calling ld-linux.so.2 explicitly, but there is no equivalient on Windows. Luckily there is a framework from Microsoft Research which can do this for you called Detours. You can find this here: link.
The demoscene group Farbrausch made a demo-capturing tool named kkapture which makes use of the Detours library. Their tool targets applications that require no user input however, so they basically run the demos at a fixed framerate by hooking into all the possible time functions, like timeGetTime(), GetTickCount() and QueryPerformanceCounter(). It's totally rad. A presentation written by ryg (I think?) regarding kkapture's internals can be found here. I think that's of interest to you.
For more information about Windows hooks, see here and here.
EDIT:
This idea intrigued me, so I used Detours to hook into OpenGL applications and mess with the graphics. Here is Quake 2 with green fog added:
Some more information about how Detours works, since I've used it first hand now:
Detours works on two levels. The actual hooking only works in the same process space as the target process. So Detours has a function for injecting a DLL into a process and force its DLLMain to run too, as well as functions that are supposed to be used in that DLL. When DLLMain is run, the DLL should call DetourAttach() to specify the functions to hook, as well as the "detour" function, which is the code you want to override with.
So it basically works like this:
You have a launcher application who's only task is to call DetourCreateProcessWithDll(). It works the same way as CreateProcessW, only with a few extra parameters. This injects a DLL into a process and calls its DllMain().
You implement a DLL that calls the Detour functions and sets up trampoline functions. That means calling DetourTransactionBegin(), DetourUpdateThread(), DetourAttach() followed by DetourTransactionEnd().
Use the launcher to inject the DLL you implemented into a process.
There are some caveats though. When DllMain is run, libraries that are imported later with LoadLibrary() aren't visible yet. So you can't necessarily set up everything during the DLL attachment event. A workaround is to keep track of all the functions that are overridden so far, and try to initialize the others inside these functions that you can already call. This way you will discover new functions as soon as LoadLibrary have mapped them into the memory space of the process. I'm not quite sure how well this would work for wglGetProcAddress though. (Perhaps someone else here has ideas regarding this?)
Some LoadLibrary() calls seem to fail. I tested with Quake 2, and DirectSound and the waveOut API failed to initalize for some reason. I'm still investigating this.

I found a sourceforge'd project called taksi:
http://taksi.sourceforge.net/
Taksi does not provide audio capture, though.

I've written screen grabbers in the past (DirectX7-9 era). I found good old DirectDraw worked remarkably well and would reliably grab bits of hardware-accelerated/video screen content which other methods (D3D, GDI, OpenGL) seemed to leave blank or scrambled. It was very fast too.

How can I know if the user has made a screenshot?

I'm writing a small c# program, I don't want the final user to take screenshots while using my program, is it possible? Or even if he takes one, how can I know it?
Thanks in advance and sorry if this is a poor-content question due to my lack of experience in c# coding.

You can create a system-wide keyboard hook using the low-level keyboard filter and cancel any printscreen keyboard combination. But if someone has also installed a helper application (like Gadwin or something) it'll become a lot more difficult because you won't know beforehand what keyboard shortcut you should catch (most tools allow to specify your own hooks).
Here's an article on using hooks in C#
and here's a ready-made keyboard hook library for .net that uses global mouse and keyboard hooks (use Google to find more freeware and commercial libraries and tools).
On a side note: it's generally not preferred to change the system behavior. Screenshots are system behavior and serve a distinguished purpose for trouble shooting. If you prevent this, users will not be able to show you a screenshot of something wrong. But if you must do it, you can do it.
EDIT: on a deeper level, you can install an API hook. All screenshot applications use API calls to get the content of a (part of) the screen. But API hooks are hard to get right. A more trivial way is probably by writing a user-level driver. While you can prevent all this, it is really worth all the trouble?

You might want a keyboard hook. But it'll tell you if the user pressed the "print screen" key, not if someone programmatically take a screenshot using some GDI function.
I doubt it's possible to prevent all the ways of taking a screenshot.

General answer: No. It's not possible to detect this - especially from C#. There are dozens of ways to take screenshot and even applications written in C++/WinAPI can only detect some of them, but not all.
Also consider - what if user is running your app in virtual machine? He'll be able to take screenshots at host machine and you can do absolutely nothing to detect (not even prevent) this.

Getting input into a process

While talking with a friend over yahoo messenger, I told him would be really cool to make a bot to answer with generic messages when someone starts a conversation. Upon thinking about what I told him, I realized it would be quite interesting to do something like that. The problem is that I don't know much about win32.
So my question is this: how do you 'link' a process to both another one and the windows environment? The goal would be to have an application running in the background which makes some sort of a query to see what windows are opened and when a new yahoo messenger conversation window appears it should send a list of keystroke events to that window.
I could use either C# or VC++ for the programming part and I can use any help: either specific answers or tips that could help me - e.g.: what to google for. So far my google research only came up with some apps/dlls/code that do that for you and some scripting stuff and I'm not exactly searching for that. I want to do all the work myself so I can learn from it.

It seems like you basically want to control other applications.
There are roughly 2 ways to do this on windows
1 - Use the low level windows API to blindly fire keyboard and mouse events at your target application.
The basic way this works is using the Win32 SendInput method, but there's a ton of other work you have to do to find window handles, etc, etc
2 - Use a higher level UI automation API to interact with the application in a more structured manner.
The best (well, newest anyway) way to do this is using the Microsoft UI Automation API which shipped in windows vista and 7 (it's available on XP as well). Here's the MSDN starter page for it.
We use the microsoft UI automation API at my job for automated UI testing of our apps, and it's not too bad. Beware though, that no matter how you chose to solve this problem, it is fraught with peril, and whether or not it works at all depends on the target application.
Good luck

Not quite the same domain as what you're looking for, BUT this series of blog posts will tell you what you need to know (and some other cool stuff).
http://www.codingthewheel.com/archives/how-i-built-a-working-poker-bot

If you really want to learn everything from scratch, then you should use C++ and native WIN32 API functions.
If you want to play a bit with C#, then you should look the pinvoke.net site and Managed Windows API project.
What you'll surely need is the Spy++ tool.

http://pinvoke.net/ seems to be the website you are looking for. The site explains how to use Windows API functions in higher level languages. Search on pinvoke for any of the functions I've listed below and it gives you the code necessary to be able to use these functions in your application.
You'll likely want to use the FindWindow function to find the window in which you're interested.
You'll need the process ID, so use GetWindowThreadProcessId to grab it.
Next, you'll need to use OpenProcess allow for reading of the process's memory.
Afterwards, you'll want to use ReadProcessMemory to read into the process's memory to see what happening with it.
Lastly, you'll want to use the PostMessage function to send key presses to the window handle.
Welcome to the wonderful world of Windows API programming.

Check out Autohotkey. This is the fastest way to do what you want.

automating .NET applications

I'm trying to automate a hidden .NET application, with another .NET application (written in c#) using the easiest way possible. It's NOT for testing purposes, it's a way to fulfill the lack of scripting for this application.
I already tried white framework, but there is one major problems with it: the way it's working. It's slow and it's not working on hidden windows and controls (like the winAPI does). Whats more, when "clicking" white moves the mouse, brings it's targeted window to the front and so on.
I was also thinking about using a user32.dll wrapper, because the way it's handling it's target is what I need, but I've red it's not working with .NET applications. It also would be a problem working with it, because my targeted application got 5 button labeled "...", and would be really hard finding 2 of them I need. I also would like to use the controls .NET id (the name the developer gave to it's controls when designing the GUI).
BTW, my targeted application is MeGUI if that helps. We do a lot of video encoding and a tool like this would help us a lot. I need the MeGUI to be hidden, because I'm the only programmer, others using my tool shouldn't see what happens in the background, not to talk about the many windows popping all around.

You can add a reference to the exe from your project and then create an AppDomain to run its main method. From there, it should be possible to queue delegates to its main thread's loop. With a bit of reflection, you could have those delegates invoke the click events and whatnot directly.
I've never attempted this approach, but it should work.

You should try Stephens idea instead of scripting a hidden app. A .NET Windows Forms App (EXE) is still a .NET Assembly and that means you can use that the same way as a DLL, just add a reference and use the public classes.
If you still want to try some scripting, take a look on the "Microsoft UI Automation" API and the "System.Windows.Automation" namespace.
Nice article here: http://msdn.microsoft.com/en-us/magazine/cc163465.aspx
MSDN Doc: http://msdn.microsoft.com/en-us/library/system.windows.automation.aspx

Need help in finding name of specific thing I'm trying to do

I think it's possible to somehow hook with the windows environment (specifically explorer.exe) and trigger specific things, for example launching control panel and using it as if I had mouse (meaning I'm clicking the interface from the code).
Basically what I'm trying to do is automate some redundant tasks I do often, just I don't know how it's done, or even how it's called. Anyone can point me in right direction?
Thanks!

Forget about "automated clicking". GUI tools are just front-ends to control the system. You can control the system like they do, it will be much easier.
Huge possibilities can give you Microsoft Management Console. Each "snap-in" can be accessed via COM model. Some of them have GUI front-ends, find and fire "*.msc" files (somewhere in Windows directory) to try them.
There is many command line tools i.e. "net" command has huge abilities related to networking.
PowerShell may be a better choice instead of C# or C++, it's designed for task automation. You can easily use COM, .NET, MMC ...

Windows Explorer has a COM object model that you can call from both C# and C++. (Most of the examples on MSDN are in Javascript or VBScript, which I guess aren't your languages of choice, but they demonstrate that the API is straightforward to call.)

AutoHotKey is a scripting environment specifically designed for this sort of task

If you want mostly to launch control panel you can do using RunDll32 interface existing in the most control panel applets. See http://www.osattack.com/windows-7/huge-list-of-windows-7-shell-commands/ , http://support.microsoft.com/kb/167012 or http://www.winvistaclub.com/t57.html for example. For the corresponding API see http://support.microsoft.com/kb/164787.
Another option is usage of control.exe (see http://msdn.microsoft.com/en-us/library/cc144191.aspx and http://vlaurie.com/computers2/Articles/control.htm).
If you google more you will find much more examples which you can to automate a lot of things without using of some general ways to automate GUI.

At more or less the lowest level within Win32, you can use the SendMessage() API to send raw click messages to windows of interest. This will rely on a lot of intrusive knowledge about the apps you intend to drive. However, you could easily implement a "click recorder" that could replay click sequences captured from user interaction.