We have a C# (WPF) application in which we want to take a screenshot of an arbitrary application launched by us (i.e. so we have a reference to the Process we started).
The application may be minimized or behind other windows but we still only want the image of the individual application, not overlapping pixels.
I know the typical P/Invoke solutions using BitBlt or PrintWindow work most of the time, but those fail (I only get black/transparent pixels) when dealing with an DirectX or OpenGL application that draws directly to the graphics device. I have found this article on taking a screenshot of a Direct3D app from C#, so I think I have that case covered.
So my question is this:
How would I do this for an OpenGL application?
What is the easiest way to determine the appropriate method to use (PW/DX/GL)?
Is there a single universal way of doing this?
For #2, am I relegated to inspecting the modules loaded by the executable and seeing if an DirectX or OpenGL DLL/Assembly is loaded?
This only has to run on Windows XP (not cross-platform and not going to Vista/7 anytime soon if ever for this application).
Answer to 1: In OpenGL, you can call glReadBuffer and glReadPixels to get the screen bitmap. However, this is slow (so you don't call it repeatedly every frame) and you might also have problems when th GL window is overlapped by another application / window. The correct way to do this is to "render to texture" (google it) by using a pbuffer.
Idea for 2: If you have the handle to window, you might be able to get the pixelformatdescriptor structure it has and check it. Never tried it though.
For 3: By the way, I don't think there is a single universal way of doing this without any problems..
Related
I want to take a screenshot of the user's currently active window (and run OCR on top of it at a later stage). This (e.g. described here) works fine as long as the developer works on standard monitors with the same resolution.
The problem is, that WPF uses device-independent units and the native API functions require pixels. I found many resources how to fix this for my own WPF application, most prominantly here and here. However, I found no way to do this dependent on what monitor the window is currently shown. For example, if the developer has a laptop with a QHD dipslay and uses a secondary monitor with a normal HD resolution. I found a C++ solution on MSDN, but not in C#.
Does anyone have experience with this or any suggestions?
Thanks.
Does anyone know how to apply effects to the entire screen, in c# or any programming language.
I'm mostly interested in making the screen monochrome (specifically green-white instead of black white).
I know a cross-graphic card solution is possible because I found a program that can do it:
http://www.freedomscientific.com/products/lv/magic-bl-product-page.asp
Anyone knows how to accomplish something this or where to look?
Thanks !!
There is no easy Windows API to modify the entire screen contents. But this could be done at the device driver level.
Otherwise you have to resort to some Windows API tricks: place a "fake" window over the entire desktop, in a loop: grab the entire screen contents without grabbing fake window contents, do your processing to get the monochrome effect, then display that on the fake window. Yes, it's hacky and slow, but possible. Even more hacky, when you get mouse clicks to "go through" the fake window (lots of SetWindowsRgn calls).
So cross-platform here means using GDI, though some older DirectDraw APIs might work, in that case, you have a much easier time with hardware overlays (and better performance). Though I'm not sure how many cards actually support hardware overlays, and if newer versions of windows support the older DirectDraw APIs.
One more possibility is if the video card has a C# or C++ or C API, then you can do whatever you want with the card without writing device driver code.
Then there's CUDA, but I haven't yet tried that out. I know it's for stream processing on nVidia boards, but I wonder if it could get you an easy backdoor into the video display stuff.
To help people in the future who are interested in this:
This is possible with the Magnification API's color effect method. This allows one to use a matrix that can be applied to the whole screen.
NegativeScreen is an open source project that implements the feature you are describing in C#.
Unfortunately, this only works with affine transformations, as the API takes only an augmented matrices rather than a delegate or something.
I've written a WPF application (in Visual C# 2010 Express) that has 2 windows. The 1st has a various buttons, the other displays video using the MediaElement control. When a button is pressed, a video associated with it is played or stopped if it's already playing.
On my development machine (Windows 7, good graphics card, lots of memory etc), this runs fine. The only problem I've encountered is that when attached to the debugger it is very unstable but when run normally these issues go away.
Unfortunately when run on a much less powerful XP machine the videos run at 1-2fps. This is despite the fact that the videos run fine in Windows Media Player.
There seem to quite a lot of reports of poor performance for the MediaElement control (not to mention inconsistencies in what it can play) so I decided to look at some alternatives.
I tried a free library call WPF MediaKit (http://wpfmediakit.codeplex.com) that I thought might have some effect, however while I've got it to work on an XP machine, it resolutely refuses to display videos on my development machine despite using exactly the same code. I'm still hoping I can this to work but I'm not confident it will help given it's still using the MediaElement control behind the scenes.
I then tried using wmp.dll COM control (Windows forms rather than WPF) and even with the simplest app (new Windows Form project, WMP control added to form, and 1 line of code to set the URL on load) I get odd behaviour. With the debugger attached, it works across multiple monitors, but sometimes when it starts playing, it just repeatedly stutters over the 1st few frames and the only way to break it out of this seems to be to move it to the other monitor. If I'm not using the debugger, I don't seem to get the stutter issue but the video is only displayed on the main monitor, as soon as I move the window to the secondary monitor, it goes black.
So my question is has anyone experienced anything like the above and/or have a decent solution to it? It would be especially nice to find something that works consistently with and without the debugger attached!
Have you tried this library?
http://directshownet.sourceforge.net/about.html
There's also this .NET interface to VideoLAN media player, but that introduces a dependency to VLC:
http://wiki.videolan.org/.Net_Interface_to_VLC
WPF MediaKit does not use MediaElement behind the scenes, but instead uses the D3DImage interop class to provide high performance video to WPF.
WPF in XP has always been a hit-or-miss in terms of performance. You might want to take a look at the rendering tier to ensure WPF is fully hardware accelerating. Also make sure you have the newest video drivers available and that the GPU is capable.
-Jer
Okay, here's what I'm trying to do. First I'll explain the end result I'm trying to achieve in case there are other ideas on how to do this.
I'm making a screen capture utility that takes a screen shot of only one window... my window (which I have total programmatic control over). However, this window may be much larger than the desktop of the computer on which the utility will run. The height, in particular, may reach several thousand pixels on a computer with 1024x768 resolution.
So I'm trying to capture the full window even though it's much larger than the screen. That's the end result I'm trying to achieve.
One hypothetical solution to this is to render the form/control on a graphics or screen object of some sort, and take the screen shot off of that object, instead of taking a screen shot of the physical desktop.
Essentially I need to draw controls on an imaginary screen that exists only in code and memory and I don't even know what to search for, so even ideas on what to put into Google (the TRUE search engine) would be helpful.
Any ideas? Thanks in advance!
EDIT: I'm using WinForms.
You didn't mention which technology your C# application uses, I'm assuming it's either WinForms or WPF.
If your implementation uses WPF, you could simply render it to a DrawingImage with the right dimensions - or even use the printing capabilities of WPF to "print" the contents of the window to an image in memory. Here's a decent example of printing in WPF that you may be able to adapt (if you're using WPF).
With a WinForms application, it is a bit trickier, because WinForm controls don't always scale well under higher resolutions, and can exhibit alignment problems. Here's a link that describes printing a WinForm screen to an image. It demonstrates printing a UserControl, but you should be able to adapt the implementation for your purposes.
Hmm, that's very odd. Have you actually written this form yet? The Form class is extremely insistent that its Size can never be larger than the screen. I've never found a workaround for this and have never seen one posted in a WF related forum.
Anyhoo, you can't make a screen shot because you don't have enough screen. The only other option is Control.DrawToBitmap().
"Several thousands of pixels" is liable to get you into trouble with OutOfMemory exceptions on 32-bit operating systems when you try to create the bitmap. Not because you don't have enough memory but because there isn't an empty hole left in the virtual memory address space that is large enough to fit the bitmap The only good workaround for that is a 64-bit operating system.
Duplicate:
Is it possible to achieve the “Aero Glass” look on XP?
If I use Winforms and I write a win32 application with it, I can see the Aero glass effects in Vista but not in XP.
How could I achieve the same look across different platforms? I am using WPF.
As a side question, did Microsoft write the Aero glass effects using WPF? If so, shouldn't the glass effect be the default WPF look on the other platforms?
What "Aero effect" are you referring to? If you're talking about the window glass, then I'm afraid you're out of luck, as the glass effect is made possible only through Vista's Desktop Window Manager.
If you're simply looking for window transparency, rounded corners, etc., then this is certainly possible in XP. Check out this article for more information.
Ok, so most of the DWM stuff is handled by a DLL called dwmapi.dll, it is all in C++ COM because that is how Microsoft writes it's APIs, you may have noticed that to call the methods in the API you have to use some unmarshalled boolean types etc, this is because it has to reach unmanaged code, some of the operations that need to take place are too dangerous for .NET to watch over without interfering, you may also notice that all the return types aren't actually returns you put in Vars as "out" types so the code can modify them in memory and then that information can be read back into your managed .NET code. As far as a way to get similar effects in Windows XP, the only way I can think of is using Windows Blinds and then making a translucent WPF form with a gradient background (with a glass like effect) it would be quite easy to do, but the window will look out of place in Vista and XP and I don't think that it is such a good idea.
Hope this helps :P
Simon