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The following Visual C++ code segment
can be used to save a HBITMAP object in to BMP file format.
void WriteBMPFile(HBITMAP bitmap, LPTSTR filename, HDC hDC)
{
BITMAP bmp;
PBITMAPINFO pbmi;
WORD cClrBits;
HANDLE hf; // file handle
BITMAPFILEHEADER hdr; // bitmap file-header
PBITMAPINFOHEADER pbih; // bitmap info-header
LPBYTE lpBits; // memory pointer
DWORD dwTotal; // total count of bytes
DWORD cb; // incremental count of bytes
BYTE *hp; // byte pointer
DWORD dwTmp;
// create the bitmapinfo header information
if (!GetObject( (bitmap, sizeof(BITMAP), (LPSTR)&bmp)){
AfxMessageBox("Could not retrieve bitmap info");
return;
}
// Convert the color format to a count of bits.
cClrBits = (WORD)(bmp.bmPlanes * bmp.bmBitsPixel);
if (cClrBits == 1)
cClrBits = 1;
else if (cClrBits <= 4)
cClrBits = 4;
else if (cClrBits <= 8)
cClrBits = 8;
else if (cClrBits <= 16)
cClrBits = 16;
else if (cClrBits <= 24)
cClrBits = 24;
else cClrBits = 32;
// Allocate memory for the BITMAPINFO structure.
if (cClrBits != 24)
pbmi = (PBITMAPINFO) LocalAlloc(LPTR,
sizeof(BITMAPINFOHEADER) + sizeof(RGBQUAD) * (1<< cClrBits));
else
pbmi = (PBITMAPINFO) LocalAlloc(LPTR, sizeof(BITMAPINFOHEADER));
// Initialize the fields in the BITMAPINFO structure.
pbmi->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
pbmi->bmiHeader.biWidth = bmp.bmWidth;
pbmi->bmiHeader.biHeight = bmp.bmHeight;
pbmi->bmiHeader.biPlanes = bmp.bmPlanes;
pbmi->bmiHeader.biBitCount = bmp.bmBitsPixel;
if (cClrBits < 24)
pbmi->bmiHeader.biClrUsed = (1<<cClrBits);
// If the bitmap is not compressed, set the BI_RGB flag.
pbmi->bmiHeader.biCompression = BI_RGB;
// Compute the number of bytes in the array of color
// indices and store the result in biSizeImage.
pbmi->bmiHeader.biSizeImage = (pbmi->bmiHeader.biWidth + 7) /8 *
pbmi->bmiHeader.biHeight * cClrBits;
// Set biClrImportant to 0, indicating that all of the
// device colors are important.
pbmi->bmiHeader.biClrImportant = 0;
// now open file and save the data
pbih = (PBITMAPINFOHEADER) pbmi;
lpBits = (LPBYTE) GlobalAlloc(GMEM_FIXED, pbih->biSizeImage);
if (!lpBits) {
AfxMessageBox("writeBMP::Could not allocate memory");
return;
}
// Retrieve the color table (RGBQUAD array) and the bits
if (!GetDIBits(hDC, HBITMAP(bitmap), 0, (WORD) pbih->biHeight,
lpBits, pbmi,
DIB_RGB_COLORS)) {
AfxMessageBox("writeBMP::GetDIB error");
return;
}
// Create the .BMP file.
hf = CreateFile(filename, GENERIC_READ | GENERIC_WRITE, (DWORD) 0,
NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL,
(HANDLE) NULL);
if (hf == INVALID_HANDLE_VALUE){
AfxMessageBox("Could not create file for writing");
return;
}
hdr.bfType = 0x4d42; // 0x42 = "B" 0x4d = "M"
// Compute the size of the entire file.
hdr.bfSize = (DWORD) (sizeof(BITMAPFILEHEADER) +
pbih->biSize + pbih->biClrUsed
* sizeof(RGBQUAD) + pbih->biSizeImage);
hdr.bfReserved1 = 0;
hdr.bfReserved2 = 0;
// Compute the offset to the array of color indices.
hdr.bfOffBits = (DWORD) sizeof(BITMAPFILEHEADER) +
pbih->biSize + pbih->biClrUsed
* sizeof (RGBQUAD);
// Copy the BITMAPFILEHEADER into the .BMP file.
if (!WriteFile(hf, (LPVOID) &hdr, sizeof(BITMAPFILEHEADER),
(LPDWORD) &dwTmp, NULL)) {
AfxMessageBox("Could not write in to file");
return;
}
// Copy the BITMAPINFOHEADER and RGBQUAD array into the file.
if (!WriteFile(hf, (LPVOID) pbih, sizeof(BITMAPINFOHEADER)
+ pbih->biClrUsed * sizeof (RGBQUAD),
(LPDWORD) &dwTmp, ( NULL))){
AfxMessageBox("Could not write in to file");
return;
}
// Copy the array of color indices into the .BMP file.
dwTotal = cb = pbih->biSizeImage;
hp = lpBits;
if (!WriteFile(hf, (LPSTR) hp, (int) cb, (LPDWORD) &dwTmp,NULL)){
AfxMessageBox("Could not write in to file");
return;
}
// Close the .BMP file.
if (!CloseHandle(hf)){
AfxMessageBox("Could not close file");
return;
}
// Free memory.
GlobalFree((HGLOBAL)lpBits);
}
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