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I'm thinking about an alternative solution to the question I posted about using Direct Show to modify/display frames from a video stream in real-time.
Instead of trying to access the video stream, I wonder if I can put code in WM_Paint to draw on top of the video output?
The code below tries to simply draw rectangles over a a dialog, where Direct Show is being used to display camera output. But in the code below, the video output draws over the GDI output. In this case, I want the GDI drawn on top of the video images.
In the final solution, I want to copy the video frame that is shown on the window, modify the copy, and then place the modified copy on top of the video.
Instead of trying to access the video stream, I wonder if I can put code in WM_Paint to draw on top of the video output?
The code below tries to simply draw rectangles over a a dialog, where Direct Show is being used to display camera output. But in the code below, the video output draws over the GDI output. In this case, I want the GDI drawn on top of the video images.
In the final solution, I want to copy the video frame that is shown on the window, modify the copy, and then place the modified copy on top of the video.
Code:
'Compilable Example:
#Compile Exe
#Dim All
#Debug Error On
#Debug Display On
%Unicode = 1
#Include "Win32API.inc"
#Include Once "dshow.inc"
#Include "qedit.inc"
Global hDlg, hDC, wRes, hRes As Dword
Global pBuffer As String Ptr, pBufferSize As Long
Global pGraph As IGraphBuilder 'Filter Graph Manager
Global pBuild As ICaptureGraphBuilder2 'Capture Graph Builder
Global pSysDevEnum As ICreateDevEnum 'enumeration object
Global pEnumCat As IEnumMoniker
Global pMoniker As IMoniker 'contains information about other objects
Global pceltFetched As Dword
Global pCap As IBaseFilter 'Video capture filter
Global pControl As IMediaControl
Global pWindow As IVideoWindow 'Display Window
Function PBMain() As Long
Dialog Default Font "Tahoma", 12, 1
Dialog New Pixels, 0, "DirectShow SampleGrabber Test",300,300,640+150,480, %WS_OverlappedWindow Or %WS_ClipSiblings Or %WS_ClipChildren To hDlg
Dialog Show Modal hDlg Call DlgProc
End Function
CallBack Function DlgProc() As Long
Local w,h As Long, PS As PaintStruct
Select Case Cb.Msg
Case %WM_InitDialog
pGraph = NewCom ClsId $CLSID_FilterGraph 'filter graph
pBuild = NewCom ClsId $CLSID_CaptureGraphBuilder2 'capture graph builder
pSysDevEnum = NewCom ClsId $CLSID_SystemDeviceEnum 'enumeration object
DisplayFirstCamera
Case %WM_Command
Select Case Cb.Ctl
End Select
Case %WM_Paint
'draw on dialog
hDC = BeginPaint(hDlg, PS)
Rectangle hDC, 20,20,200,200
Rectangle hDC, 60,60,100,100
EndPaint hDlg, PS
Case %WM_Destroy
pGraph = Nothing
pBuild = Nothing
pSysDevEnum = Nothing
Case %WM_Size
Dialog Get Client hDlg To w,h
pWindow.SetWindowPosition(150,0,w-150,h)
End Select
End Function
Sub DisplayFirstCamera
If pSysDevEnum.CreateClassEnumerator($CLSID_VideoInputDeviceCategory, pEnumCat, 0) <> %S_Ok Then Exit Sub
pEnumCat.next(1, pMoniker, pceltFetched) 'cycle through monikders
pMoniker.BindToObject(Nothing, Nothing, $IID_IBaseFilter, pCap) 'create device filter for the chosen device
pGraph.AddFilter(pCap,"First Camera") 'add chosen device filter to the filter graph
pBuild.SetFilterGraph(pGraph) 'initialize pBuild
pBuild.RenderStream $Pin_Category_Preview, $MediaType_Video, pCap, Nothing, Nothing 'render the live source
pWindow = pGraph
pWindow.Owner = hDlg
pWindow.WindowStyle = %WS_Child Or %WS_ClipChildren Or %WS_ClipSiblings 'video window settings
pControl = pGraph
pControl.Run
End Sub
, but it is the concept I had in mind and is a good place to start testing...
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