Capturing a Window

Question

Capturing a Window

JChild 21

I am trying to capture an application's display and stream it to another computer. The application is composed of multiple program windows. I found the following examples and used them to create a window with a composition host that captures multiple windows and combines them into one window.

https://github.com/microsoft/Windows.UI.Composition-Win32-Samples/tree/master/cpp/ScreenCaptureforHWND

https://github.com/microsoft/Windows.UI.Composition-Win32-Samples/tree/master/cpp/HelloComposition/HelloComposition

When I try to capture the new window I am only able to get the new window's background color. I have tried using GDI+ (StretchBlt and BitBlt) and DirectX but they are unable to capture the new window with the combined layers. They just capture the background of the new window. The code I am writing is on a stand alone network so I am unable to post the actual source code.

Xiaopo Yang - MSFT 12,731 Reputation points Microsoft External Staff

2022-04-06T02:06:10.493+00:00

Does the new window mean a window you created with a composition host that captures multiple windows and combines them into one window?
And I have verified that the ScreenCaptureforHWND can capture the HelloComposition window. So could you please show a minimal, reproducible sample about the question without private information?
JChild 21 Reputation points

2022-04-06T18:42:29.973+00:00

I created a new window and passed the handle to the composition host. That composition host captures multiple windows and combines them. they are all then displayed in the new window that was created. When I try to use GDI+ or even BitBlt it just captures the new window that I created. It doesn't capture the windows added to the composition host.

I will see what I can do about getting a sample of the code I have posted here.
Xiaopo Yang - MSFT 12,731 Reputation points Microsoft External Staff

2022-04-07T02:21:08.023+00:00

You can post the sample without private information to GitHub or somewhere you prefer.
GDI+ might not capture the window with composition. You can try ScreenCaptureforHWND or DXGIDesktopDuplication to capture.
JChild 21 Reputation points

2022-04-08T17:10:38.127+00:00

The HelloComposition project, reference above, is close to the code I am using. I tried a test with the HelloComposition project. I can't capture the pixels of the HelloComposition window using GDI. Is there another option that would allow me to capture the pixel data of that window?
Xiaopo Yang - MSFT 12,731 Reputation points Microsoft External Staff

2022-04-11T01:05:44.483+00:00

Apart from PrintWindow @Castorix31 mentioned, you can try ScreenCaptureforHWND I've verified or DXGIDesktopDuplication to capture.
Xiaopo Yang - MSFT 12,731 Reputation points Microsoft External Staff

2022-04-11T01:42:20.54+00:00

I also test GDI Capturing an Image doesn't capture the composition.
Xiaopo Yang - MSFT 12,731 Reputation points Microsoft External Staff

2022-04-15T07:18:18.763+00:00

Hello @JChild , Any updates?
JChild 21 Reputation points

2022-04-15T19:37:15.963+00:00

Using Castorix31 suggestion with PrintWindow I am able to capture the contents of my window. PrintWindow is a pretty slow call. I was hoping there would be something that would allow me to "flatten" the composition host visual tree and get the pixels directly from the root Visual of the host. PrintWindow might be the best way to go at this point. I'm pretty new to the windows runtime library. Is there a way to get the pixels from the root Visual?

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Xiaopo Yang - MSFT 12,731 Reputation points Microsoft External Staff

2022-04-06T02:06:10.493+00:00

Does the new window mean a window you created with a composition host that captures multiple windows and combines them into one window?
And I have verified that the ScreenCaptureforHWND can capture the HelloComposition window. So could you please show a minimal, reproducible sample about the question without private information?
JChild 21 Reputation points

2022-04-06T18:42:29.973+00:00

I created a new window and passed the handle to the composition host. That composition host captures multiple windows and combines them. they are all then displayed in the new window that was created. When I try to use GDI+ or even BitBlt it just captures the new window that I created. It doesn't capture the windows added to the composition host.

I will see what I can do about getting a sample of the code I have posted here.
Xiaopo Yang - MSFT 12,731 Reputation points Microsoft External Staff

2022-04-07T02:21:08.023+00:00

You can post the sample without private information to GitHub or somewhere you prefer.
GDI+ might not capture the window with composition. You can try ScreenCaptureforHWND or DXGIDesktopDuplication to capture.
JChild 21 Reputation points

2022-04-08T17:10:38.127+00:00

The HelloComposition project, reference above, is close to the code I am using. I tried a test with the HelloComposition project. I can't capture the pixels of the HelloComposition window using GDI. Is there another option that would allow me to capture the pixel data of that window?
Xiaopo Yang - MSFT 12,731 Reputation points Microsoft External Staff

2022-04-11T01:05:44.483+00:00

Apart from PrintWindow @Castorix31 mentioned, you can try ScreenCaptureforHWND I've verified or DXGIDesktopDuplication to capture.
Xiaopo Yang - MSFT 12,731 Reputation points Microsoft External Staff

2022-04-11T01:42:20.54+00:00

I also test GDI Capturing an Image doesn't capture the composition.
Xiaopo Yang - MSFT 12,731 Reputation points Microsoft External Staff

2022-04-15T07:18:18.763+00:00

Hello @JChild , Any updates?
JChild 21 Reputation points

2022-04-15T19:37:15.963+00:00

Using Castorix31 suggestion with PrintWindow I am able to capture the contents of my window. PrintWindow is a pretty slow call. I was hoping there would be something that would allow me to "flatten" the composition host visual tree and get the pixels directly from the root Visual of the host. PrintWindow might be the best way to go at this point. I'm pretty new to the windows runtime library. Is there a way to get the pixels from the root Visual?

Answer 1

Castorix31 90,521

I tested with HelloComposition sample, and I can copy the window with
PrintWindow and PW_RENDERFULLCONTENT flag (into a compatible DC with CreateCompatibleDC)
I added a SS_BITMAP Static control where I set the copied bitmap with STM_SETIMAGE :

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Capturing a Window

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