I am currently making an OpenCV project in C++ where I look for motion with a kinect and use that to cue a slideshow (sans recognition). Currently, I am displaying the slideshow using OpenCV (as I've only had about a week to whip this up). It looks good and its quick. The only problem is that this is going to be on display for a big production and I can't really afford to have the window showing (I'm talking window decorations like the title bar and such).
I need to get rid of the title bar. I've done a lot of research, and I have found out that you can magically grab the window handle by calling cvGetWindowHandle("SlideShow"), but that is a void function, so I don't really know how I am supposed to get a handle from that to manipulate.
I'm developing this for both windows AND ubuntu, since it will end up on a windows machine, but I can only demo on a laptop running ubuntu.
If anyone can tell me how to take the window and render it fullscreen with a resized image to fill most if not the entire screen in either Windows or Ubuntu, I will be forever grateful.
I am using OpenCV 2.1 on Ubuntu 11.04. On my system CV_WINDOW_FULLSCREEN and CV_WINDOW_AUTOSIZE flags both map to 1
And both flags behave exactly the same. They give you a fixed size window, which would be expected for AUTOSIZE flag but not the FULLSCREEN. I think these two flags are meant for different functions although their simillar appearance is very confusing. The flag CV_WINDOW_NORMAL maps to value 0 which is what you have used. It gives you a resizable window that you could maximize, but it is not a fullscreen window.
Edit: I just found the solution in another stachoverflow post. Here is the solution from that post which worked great on my system:
cvNamedWindow("Name", CV_WINDOW_NORMAL);
cvSetWindowProperty("Name", CV_WND_PROP_FULLSCREEN, CV_WINDOW_FULLSCREEN);
cvShowImage("Name", your_image);
I get a real fullscreen with no title bar etc.
you can use the cv::setWindowProperty function for your purpose, just set it to CV_WINDOW_FULLSCREEN.
Full documentation in the openCV-WIKI
In opencv/4.5.1, this is how it is done:
namedWindow("Name", WINDOW_NORMAL);
setWindowProperty ("Name", WND_PROP_FULLSCREEN, WINDOW_FULLSCREEN);
Assuming you have added using namespace cv;
Related
I'm new to openCV and I'm using 3.4.1_5, C++ in Xcode on Mac. I used Homebrew to install opencv.
I'm following an openCV tutorial which is conducted in VS on Windows. Here's a link to the tutorial.
Basically, the tutorial shows how to create/resize a window, which is easy. So I have some code like this which is basically the same as in the tutorial:
#include "opencv2/opencv.hpp"
....
namedWindow("modi", CV_WINDOW_FREERATIO);
imshow("modi", modi);
resizeWindow("modi", modi.cols/2, modi.rows/2); //modi is a Mat
....
Supposedly, the image will be the same except it will be 1/4 of the original size and fit into the resized window. This is the case in the tutorial. However, it's not the case on my mac. My image stays the same size, and only the window shrinks to 1/4. If I drag the border of the window, the "covered" part of the image is revealed.
This actually poses a problem to my project later on, so I want to figure out why. I want to achieve what the tutorial achieves, and I've tried all window parameter, like AUTOSIZE, KEEPRATIO, OPENGL, etc. None of them worked. I'm thinking about if it's due to platform or version problem, but I have no way to test them.
Please help! Any hints would be greatly appreciated!
Situation: I have a software that performs screen sharing over the Internet, where one user acts as a presenter, and other users act as viewers/attendees.
Besides the presentation windows, the presenter also has a set of NON-SHARING-WINDOWS that appear on the screen (a button bar for start sharing/stop sharing/etc., a Skype window etc.).
The presenter can configure from the setup of the screen sharing software to make these NON-SHARING-WINDOWS invisible (i.e. they will not appear in the screen sharing that is being sent to the attendees, but the window content behind them will appear in the screenshot).
The screenshots are sent at approximately 10 frames-per-second, or faster.
Question: how can I programmatically capture the screen, except for these NON-SHARING-WINDOWS windows?
Notes:
Because of the higher frames-per-second value, I cannot minimize/maximize/set alpha for these windows, because then the windows will flicker. The application is written in Win32 C++.
I would use layered windows, but because of the Windows 7 Desktop Composition feature, this is not usable out-of-the-box (and in Windows 8, you cannot use DwmEnableComposition anymore to temporarily and programmatically disable composition)
I could use the layered window approach for Windows XP/2000/7 etc., and a different approach for Windows 8 (if there is one), though I would prefer a single process that works on all systems
I could also try to "compose" the screenshots by capturing individual images (of the desktop, the windows that need to be captured) and using their z-index to create the final image, but because of the required frames-per-second value, this process would be too slow.
In windows even the desktop is considered a window and has its own HWND.
It seems however, not easily possible to only copy the "wallpaper" on its own.
So i basically see two ways to do that.
1. Copy the entire desktop e.g. BitBlt(GetWindowDC(GetDesktopWindow()),...)
OR
Use GetWindow and traverse the window list in backward direction starting from the Desktop-Window whose HWND you just can determine with GetDesktopWindow(), Like this:
// paint on a black DC
hwnd=GetDesktopWindow()
while (hwnd = GetWindow(hwnd, GW_HWNDPREV))
{
// is this window not shared? continue
// else bitblt it into our dc
}
Hope i gave some inspiration :-)
If someone knows a way how to copy ONLY the desktop without its child windows please let me know.
You can use Magnifier API.
There is a function in magnifier API that allows you to exclude specific windows from your target window (your window with 1x magnification where magnifier renders).
You can set this window to full screen and make it transparent and then use PrintWindow function.
The function: https://learn.microsoft.com/en-us/windows/desktop/api/magnification/nf-magnification-magsetwindowfilterlist
Sample projects:
https://www.codeproject.com/Articles/607288/Screenshot-using-the-Magnification-library
https://code.msdn.microsoft.com/windowsdesktop/Magnification-API-Sample-14269fd2
I'm aware this question is pretty old, but I ran into the same problem and it was very, very hard to find any information at all regarding this.
Since Windows 10 version 2004 (build 10.0.19041), the SetWindowDisplayAffinity API has been expanded to include a flag called WDA_EXCLUDEFROMCAPTURE (0x00000011). This will remove the window from images captured with BitBlt
The window is displayed only on a monitor. Everywhere else, the window does not appear at all.
One use for this affinity is for windows that show video recording controls, so that the controls are not included in the capture.
Introduced in Windows 10 Version 2004. See remarks about compatibility regarding previous versions of Windows.
For versions before 2004, it will use the existing WDA_MONITOR flag.
I have tested this with a screen capture of the desktop and I am unsure what would happen if you were to use a window DC.
So I guess a possible solution would be:
// get window handle
hWnd = (...)
BOOL result = SetWindowDisplayAffinity(m_hWnd, WDA_EXCLUDEFROMCAPTURE);
// do bitblt stuff
mabye you can use Magnification API, even Microsoft said The MagImageScalingCallback function is deprecated in Windows 7 and later, and should not be used in new applications. There is no alternate functionality., but it still work on Windows 10;
Here is the overview of this API : https://learn.microsoft.com/en-us/previous-versions/windows/desktop/magapi/magapi-intro
The sample code of Microsoft is here : https://github.com/microsoft/Windows-classic-samples/tree/main/Samples/Magnification
If you want to get the screenshot rgb data, you can use this api MagSetImageScalingCallback to set callback of Magnifier window, every time you use MagSetWindowSource or InvalidRect of magnifer window, this callback function MagImageScalingCallback will be called, so you can get screenshot rgb data here.
I think that to limit the capture content within a big window will be more simple. otherwise you will need to cut some windows from the screen capture.
I've seen things like this and I was wondering if this was possible, say I run my application
and it will show the render on whatever is below it.
So basically, rendering on the screen without a window.
Possible or a lie?
Note: Want to do this on windows and in c++.
It is possible to use your application to draw on other application's windows. Once you have found the window you want, you have it's HWND, you can then use it just like it was your own window for the purposes of drawing. But since that window doesn't know you have done this, it will probably mess up whatever you have drawn on it when it tries to redraw itself.
There are some very complicated ways of getting around this, some of them involve using windows "hooks" to intercept drawing messages to that window so you know when it has redrawn so that you can do your redrawing as well.
Another option is to use clipping regions on a window. This can allow you to give your window an unusual shape, and have everything behind it still look correct.
There are also ways to take over drawing of the desktop background window, and you can actually run an application that draws animations and stuff on the desktop background (while the desktop is still usable). At least, this was possible up through XP, not sure if it has changed in Vista/Win7.
Unfortunately, all of these options are too very complex to go in depth without more information on what you are trying to do.
You can use GetDesktopWindow(), to get the HWND of the desktop. But as a previous answer says (SoapBox), be careful, you may mess up the desktop because the OS expects that it owns it.
I wrote an open source project a few years ago to achieve this on the desktop background. It's called Uberdash. If you follow the window hierarchy, the desktop is just a window in a sort of "background" container. Then there is a main container and a front container. The front container is how windows become full screen or "always on top." You may be able to use Aero composition to render a window with alpha in the front container, but you will need to pass events on to the lower windows. It won't be pretty.
Also, there's a technology in some video cards called overlays/underlays. You used to be able to render directly to an overlay. Your GPU would apply it directly, with no interference to main memory. So even if you took a screen capture, your overlay/underlay would not show up in the screen cap. Unfortunately MS banned that technology in Vista...
On Windows (Vista32), I want to display some simple graphics on top of a fullscreen flash window (an overlay of useful information while using the flash application). What's the fastest way to accomplish it?
I think I may be able to achieve it using DirectX with the DDSCAPS_OVERLAY flag but with the only example I've found I get an exception:
E_NOTIMPL
The function called is not supported at this time
on
m_direct_draw->CreateSurface(&ddsd, &m_overlay_surface, 0)
(full code here: http://nexe.gamedev.net/files/Overlay-2005-11-21.zip)
Something relevant to C/++ or Python would help me. I'm using the latest DirectX SDK.
Thank you
Just create a Layered Window and draw to it with an alpha channel - in WPF, this is as easy as setting the AllowsTransparency bit on the Window
While the transparent layered window is useful, it doesn't appear on top of the fullscreen flash with WS_EX_TOPMOST set.
Note sure how to reply to Paul sadly.
Overlaying on a 3D fullscreen application is very relevant but while it works and flash appears to load dx9, it doesn't show on flash.
I have an application with an OpenGL window as a child window of the main window.
When I display a dialog box above the OpenGL window, it doesn't get drawn. It's like it's not getting WM_PAINT messages. If I can guess the title bar position of the dialog box, I can drag it and it's still responsive.
I realise this might be a vague question, but I was wondering if anyone else has seen this sort of behaviour before and knew of a solution?
I wondered if the Pixel Format Descriptor would make a difference - I had PFD_DRAW_TO_WINDOW, but changing to PDF_DRAW_TO_BITMAP didn't make any difference. I'm not sure what else I should be looking at?
Bugger. Should have given all the details. I was running Windows in a virtual machine on Mac OS X using Parallels. I upgrade from Parallels 3 to 4 and now everything is working fine. I suspect a Parallels video driver issue.
Thanks to all those who answered with suggestions.
Is your opengl window constantly rendering. It is possible that the 3D hardware is simply rendering into an overlay that is overdrawing your dialog box. If you position the dialog box so it overlaps your main window, can you see some of it?
Try to pause rendering into the main display to see if it effects the results.
You will also need to make sure that your window style ensures the results are clipped...
cs.style |= WS_CLIPSIBLINGS | WS_CLIPCHILDREN ;
You should check though all the items mentioned in this MSDN article, as it covers a lot of the basics for getting opengl rendering in a window correctly.
http://msdn.microsoft.com/en-us/library/ms970745.aspx
You may need to switch overlay off. It can be done via forcing back buffer presenting method to copy instead of swap.
Use wglChoosePixelFormatARB and one of parameters should be
WGL_SWAP_METHOD_ARB with value WGL_SWAP_COPY_ARB
This may seems stupid but are you sure your OpenGL window is not flagged "topmost" ?
Does the dialog box disappear also behind borders of your window or just behind the OpenGL rendering rectangle ?