mfc, How do you save a CBitmap to a BMP file

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mfc >> How do you save a CBitmap to a BMP file

by moogle33 » Thu, 27 Nov 2003 17:38:57 GMT

Does anybody know how to do this ?
You would think it would be easy... The internet has loads of references to
loading BMP's into CBitmaps but none for the other way round :(

James



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mfc >> How do you save a CBitmap to a BMP file

by David A. Mair » Fri, 28 Nov 2003 03:12:52 GMT





to

Here's some code I use to do it in my WebCam app:

HANDLE hf = CreateFile(bmp, GENERIC_WRITE, FILE_SHARE_READ, NULL,
CREATE_ALWAYS, NULL, NULL );

if( hf == INVALID_HANDLE_VALUE )
return false;

// write out the file header
//
BITMAPFILEHEADER bfh;
memset( &bfh, 0, sizeof( bfh ) );
bfh.bfType = 'MB';
bfh.bfSize = sizeof( bfh ) + m_CBInfo.lBufferSize + sizeof(
BITMAPINFOHEADER );
bfh.bfOffBits = sizeof( BITMAPINFOHEADER ) + sizeof( BITMAPFILEHEADER );

DWORD dwWritten = 0;
WriteFile( hf, &bfh, sizeof( bfh ), &dwWritten, NULL );

// and the bitmap format
//
VIDEOINFOHEADER * vih = (VIDEOINFOHEADER*) m_StillMediaType.pbFormat;
BITMAPINFOHEADER bih;
memset( &bih, 0, sizeof( bih ) );
bih.biSize = sizeof( bih );
bih.biWidth = vih->bmiHeader.biWidth;
bih.biHeight = vih->bmiHeader.biHeight;
bih.biPlanes = 1;
bih.biBitCount = 24;

dwWritten = 0;
WriteFile( hf, &bih, sizeof( bih ), &dwWritten, NULL );

// and the bits themselves
//
dwWritten = 0;
WriteFile( hf, m_CBInfo.pBuffer, m_CBInfo.lBufferSize, &dwWritten, NULL );
CloseHandle( hf );

Note that in CreateFile() the bmp argument is a CString holding the filename
to use when creating the file. The BITMAPINFOHEADER is what I write on the
second WriteFile(), the VIDEOINFOHEADER is only used to get the width and
height of the image since it is coming from a video stream and I'm writing
frames as-is. Note also that I do almost no error checking, you should -
I'm not finished yet. Finally, I know I have 24 bit pixels and one colour
plane, you may need to make these fields of the BITMAPINFOHEADER
configurable.




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