VMRALPHABITMAP structure (strmif.h)
[The feature associated with this page, DirectShow, is a legacy feature. It has been superseded by MediaPlayer, IMFMediaEngine, and Audio/Video Capture in Media Foundation. Those features have been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use MediaPlayer, IMFMediaEngine and Audio/Video Capture in Media Foundation instead of DirectShow, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]
The VMRALPHABITMAP structure is used in the VMR-7 filter's IVMRMixerBitmap methods when the application is providing a static alpha-blended bitmap to be displayed on the composited video frame.
Syntax
typedef struct _VMRALPHABITMAP {
DWORD dwFlags;
HDC hdc;
LPDIRECTDRAWSURFACE7 pDDS;
RECT rSrc;
NORMALIZEDRECT rDest;
FLOAT fAlpha;
COLORREF clrSrcKey;
} VMRALPHABITMAP, *PVMRALPHABITMAP;
Members
dwFlags
Flags that instruct the mixer where to find the bitmap. The following values are defined.
| Value | Meaning |
|---|---|
|
Disable the bitmap. This flag cannot be combined with other flags. |
|
Obtain the bitmap from the HDC. If this flag is set, the hdc member must specify a valid handle to a device context, and the pDDS member must be NULL.
If this flag is absent, the pDDS member must point to a valid DirectDraw surface, and the hdc member must be NULL. |
|
Take the entire DirectDraw surface. When this flag is specified, rSrc is ignored. This flag cannot be combined with the VMRBITMAP_HDC flag. |
|
The clrSrcKey value is valid and should be used when blending. |
|
Indicates that the rSrc rectangle is valid and specifies a sub-rectangle of the original app image to be blended.
This flag is only valid for the IVMRMixerBitmap::UpdateAlphaBitmapParameters method. For the IVMRMixerBitmap::SetAlphaBitmap method, the rSrc member must refer to the entire bitmap. |
hdc
The handle to the device context for the bitmap. Specify NULL if the bitmap is located in a DirectDraw surface.
pDDS
Pointer to a DirectDraw surface that contains the bitmap. Specify NULL if the bitmap is to be obtained from a GDI device context. If a DirectDraw surface is specified, the pixel format must be ARGB-32 or RGB-32. If the surface contains per-pixel alpha, do not set the VMRBITMAP_SRCCOLORKEY flag in dwFlags.
rSrc
Specifies the source rectangle in either the GDI device context or the DirectDraw surface.
rDest
Specifies the destination rectangle in composition space.
fAlpha
Specifies the alpha blending value; must be a value from 0.0 to 1.0 (inclusive).
clrSrcKey
Specifies the source color key.
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client | Windows XP [desktop apps only] |
| Minimum supported server | Windows Server 2003 [desktop apps only] |
| Header | strmif.h (include Dshow.h) |