IMediaDet::GetBitmapBits method
[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 It has been superseded by MediaPlayer, IMFMediaEngine, and Audio/Video Capture in Media Foundation.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.]
Note
[Deprecated. This API may be removed from future releases of Windows.]
The GetBitmapBits method retrieves a video frame at the specified media time. The returned frame is always in 24-bit RGB format.
Syntax
HRESULT GetBitmapBits(
double StreamTime,
long *pBufferSize,
char *pBuffer,
long Width,
long Height
);
Parameters
-
StreamTime
-
Time at which to retrieve the video frame, in seconds.
-
pBufferSize
-
Receives the required buffer size. If pBuffer is NULL, the variable receives the size of the buffer needed to retrieve the frame. If pBuffer is not NULL, this parameter is ignored.
-
pBuffer
-
Pointer to a buffer that receives a BITMAPINFOHEADER structure followed by the DIB bits.
-
Width
-
Width of the video image, in pixels.
-
Height
-
Height of the video image, in pixels.
Return value
Returns an HRESULT value. Possible values include the following:
| Return code | Description |
|---|---|
|
Success. |
|
Could not add the Sample Grabber filter to the graph. |
|
Insufficient memory. |
|
NULL pointer error. |
|
Unexpected error. |
|
Invalid media type. |
Remarks
Before calling this method, set the file name and stream by calling IMediaDet::put_Filename and IMediaDet::put_CurrentStream.
To determine the size of the buffer that is required, call this method with pBuffer equal to NULL. The size is returned in the variable pointed to by pBufferSize. Then create the buffer and call the method again, with pBuffer equal to the address of the buffer. When the method returns, the buffer contains a BITMAPINFOHEADER structure followed by the bitmap. The bitmap is scaled to the dimensions specified in the Width and Height parameters.
This method puts the media detector into bitmap grab mode. Once this method has been called, the various stream information methods in IMediaDet do not work, unless you create a new instance of the media detector.
Note
The header file Qedit.h is not compatible with Direct3D headers later than version 7.
Note
To obtain Qedit.h, download the Microsoft Windows SDK Update for Windows Vista and .NET Framework 3.0. Qedit.h is not available in the Microsoft Windows SDK for Windows 7 and .NET Framework 3.5 Service Pack 1.
Examples
The following code uses the GetBitmapBits method to create a device-independent bitmap.
long size;
hr = pDet->GetBitmapBits(0, &size, 0, width, height);
if (SUCCEEDED(hr))
{
char *pBuffer = new char[size];
if (!pBuffer)
return E_OUTOFMEMORY;
try {
hr = pDet->GetBitmapBits(0, 0, pBuffer, width, height);
}
catch (...) {
delete [] pBuffer;
throw;
}
if (SUCCEEDED(hr))
{
BITMAPINFOHEADER *bmih = (BITMAPINFOHEADER*)pBuffer;
HDC hdcDest = GetDC(0);
// Find the address of the start of the image data.
void *pData = pBuffer + sizeof(BITMAPINFOHEADER);
// Note: In general a BITMAPINFOHEADER can include extra color
// information at the end, so calculating the offset to the image
// data is not generally correct. However, the IMediaDet interface
// always returns an RGB-24 image with no extra color information.
BITMAPINFO bmi;
ZeroMemory(&bmi, sizeof(BITMAPINFO));
CopyMemory(&(bmi.bmiHeader), bmih, sizeof(BITMAPINFOHEADER));
HBITMAP hBitmap = CreateDIBitmap(hdcDest, bmih, CBM_INIT,
pData, &bmi, DIB_RGB_COLORS);
}
delete[] pBuffer;
}
Requirements
| Requirement | Value |
|---|---|
| Header |
|
| Library |
|
See also