Save an RGB24 sample to bitmap - visual-c++

Question

I'm using Windows Media Foundation to do some messing around with my webcam. I've been able to successfully retrieve a data sample from the webcam and identify that the format is RGB24. Now I'd like to save a single frame as a bitmap. A small snippet of the code I'm using to read a sample from the webcam is below.
IMFSample *pSample = NULL;
hr = pReader->ReadSample(
MF_SOURCE_READER_ANY_STREAM, // Stream index.
0, // Flags.
&streamIndex, // Receives the actual stream index.
&flags, // Receives status flags.
&llTimeStamp, // Receives the time stamp.
&pSample // Receives the sample or NULL.
);
So once I've got pSample populated with an IMFSample how can I save it as a bitmap?

Answer 1

Below is the code snippet I used to save a bitmap from an IMFSample. I've taken a lot of shortcuts and I'm pretty sure I'm only able to get away with doing things this way because my webcam defaults to returning an RGB24 stream and also a 640 x 480 pixel buffer which means there's no striping to worry about in pData.
hr = pReader->ReadSample(
MF_SOURCE_READER_ANY_STREAM, // Stream index.
0, // Flags.
&streamIndex, // Receives the actual stream index.
&flags, // Receives status flags.
&llTimeStamp, // Receives the time stamp.
&pSample // Receives the sample or NULL.
);
wprintf(L"Stream %d (%I64d)\n", streamIndex, llTimeStamp);
HANDLE file;
BITMAPFILEHEADER fileHeader;
BITMAPINFOHEADER fileInfo;
DWORD write = 0;
file = CreateFile(L"sample.bmp",GENERIC_WRITE,0,NULL,CREATE_ALWAYS,FILE_ATTRIBUTE_NORMAL,NULL); //Sets up the new bmp to be written to
fileHeader.bfType = 19778; //Sets our type to BM or bmp
fileHeader.bfSize = sizeof(fileHeader.bfOffBits) + sizeof(RGBTRIPLE); //Sets the size equal to the size of the header struct
fileHeader.bfReserved1 = 0; //sets the reserves to 0
fileHeader.bfReserved2 = 0;
fileHeader.bfOffBits = sizeof(BITMAPFILEHEADER)+sizeof(BITMAPINFOHEADER); //Sets offbits equal to the size of file and info header
fileInfo.biSize = sizeof(BITMAPINFOHEADER);
fileInfo.biWidth = 640;
fileInfo.biHeight = 480;
fileInfo.biPlanes = 1;
fileInfo.biBitCount = 24;
fileInfo.biCompression = BI_RGB;
fileInfo.biSizeImage = 640 * 480 * (24/8);
fileInfo.biXPelsPerMeter = 2400;
fileInfo.biYPelsPerMeter = 2400;
fileInfo.biClrImportant = 0;
fileInfo.biClrUsed = 0;
WriteFile(file,&fileHeader,sizeof(fileHeader),&write,NULL);
WriteFile(file,&fileInfo,sizeof(fileInfo),&write,NULL);
IMFMediaBuffer *mediaBuffer = NULL;
BYTE *pData = NULL;
pSample->ConvertToContiguousBuffer(&mediaBuffer);
hr = mediaBuffer->Lock(&pData, NULL, NULL);
WriteFile(file, pData, fileInfo.biSizeImage, &write, NULL);
CloseHandle(file);
mediaBuffer->Unlock();
I've included a bit of a discussion here.