如何将CBitmap类中的内容存为BMP文件

[ShenS]

我已经在内存中建立了内存兼容的CBitmap对象,并在CBitmap中绘制了复杂的图形,使用Bitblt将该CBitmap显示到屏幕窗口中,但不知道如何将窗口中显示的内容存为硬盘上的BMP文件,请高手赐教!谢谢

[snowhust]

zjy:能E给我一份吗？ [e-mail]

[GoldenLion]

BMP文件格式首先是文件头，它的结构与BITMAPINFOHEAD比较类似，可以用CBitmap.GetBitmap()得到；随后是调色板，如果你是真彩图，那么就没有调色板；最后是数据区，它的值是调色板索引或者在真彩时就是RGB值。

找一个BMP文件，就能很清楚它的结构了。

[zjy]

我E给你,有两套,分两次E出
告诉我E到哪个信箱

[longx]

将一个位图存进一个文件
需要分两步
1)将位图转换为与设备无关的DIB
DdbToDib(CBitmap& bitmap,DWORD dwcompression,CPalette* ppal )
2)将它写入文件中
BOOL WriteDib(LPCTSTR szfile, HANDLE hdib)

HANDLE DdbToDib(CBitmap& bitmap,DWORD dwcompression,CPalette* ppal )
{
BITMAP bm;
BITMAPINFOHEADER bi;
LPBITMAPINFOHEADER lpbi;
DWORD dwlen;
HANDLE hdib;
HANDLE handle;
HDC hdc;
HPALETTE hpal;

ASSERT(bitmap.GetSafeHandle());
// the function has no arg for bitfields
if( dwcompression == BI_BITFIELDS)
return NULL;

// if a palette has not been supplied use defaul palette
hpal = (HPALETTE) ppal->GetSafeHandle();
if (hpal==NULL)
hpal = (HPALETTE) GetStockObject(DEFAULT_PALETTE);
// get bitmap information
bitmap.GetObject(sizeof(bm),(LPSTR)&bm);

// initialize the bitmapinfoheader
bi.biSize = sizeof(BITMAPINFOHEADER);
bi.biWidth = bm.bmWidth;
bi.biHeight = bm.bmHeight;
bi.biPlanes = 1;
bi.biBitCount = bm.bmPlanes * bm.bmBitsPixel;
bi.biCompression = dwcompression;
bi.biSizeImage = 0;
bi.biXPelsPerMeter = 0;
bi.biYPelsPerMeter = 0;
bi.biClrUsed = 0;
bi.biClrImportant = 0;

// compute the size of the infoheader and the color table
int ncolors = (1 << bi.biBitCount);
if( ncolors> 256 )
ncolors = 0;
dwlen = bi.biSize + ncolors * sizeof(RGBQUAD);

// we need a device context to get the dib from
hdc =::GetDC(NULL);
hpal = SelectPalette(hdc,hpal,FALSE);
RealizePalette(hdc);

// allocate enough memory to hold bitmapinfoheader and color table
hdib = GlobalAlloc(GMEM_FIXED,dwlen);

if (!hdib)
{
SelectPalette(hdc,hpal,FALSE);
::ReleaseDC(NULL,hdc);
return NULL;
}

lpbi = (LPBITMAPINFOHEADER)hdib;

*lpbi = bi;

// call getdibits with a null lpbits param, so the device driver
// will calculate the bisizeimage field
GetDIBits(hdc, (HBITMAP )bitmap.GetSafeHandle(),0L, (DWORD)bi.biHeight,
(LPBYTE)NULL, (LPBITMAPINFO)lpbi, (DWORD)DIB_RGB_COLORS);

bi = *lpbi;

// if the driver did not fill in the bisizeimage field, then compute it
// each scan line of the image is aligned on a dword (32bit) boundary
if (bi.biSizeImage == 0)
{
bi.biSizeImage = ((((bi.biWidth * bi.biBitCount) + 31) & ~31) / 8)
* bi.biHeight;

// if a compression scheme is used the result may infact be larger
// increase the size to account for this.
if (dwcompression != BI_RGB)
bi.biSizeImage = (bi.biSizeImage * 3) / 2;
}

// realloc the buffer so that it can hold all the bits
dwlen += bi.biSizeImage;
if (handle = GlobalReAlloc(hdib, dwlen, GMEM_MOVEABLE))
hdib = handle;
else
{
GlobalFree(hdib);
// reselect the original palette
SelectPalette(hdc,hpal,FALSE);
::ReleaseDC(NULL,hdc);
return NULL;
}

// get the bitmap bits
lpbi = (LPBITMAPINFOHEADER)hdib;

// finally get the dib
int bgotbits =GetDIBits( hdc, (HBITMAP )bitmap.GetSafeHandle(),
0L, // start scan line
(DWORD)bi.biHeight, // # of scan lines
(LPBYTE)lpbi // address for bitmap bits
+ (bi.biSize + ncolors * sizeof(RGBQUAD)),
(LPBITMAPINFO)lpbi, // address of bitmapinfo
(DWORD)DIB_RGB_COLORS); // use rgb for color table

if( !bgotbits )
{
GlobalFree(hdib);
SelectPalette(hdc,hpal,FALSE);
::ReleaseDC(NULL,hdc);
return NULL;
}

SelectPalette(hdc,hpal,FALSE);
::ReleaseDC(NULL,hdc);
return hdib;
}

BOOL WriteDib(LPCTSTR szfile, HANDLE hdib)
{
BITMAPFILEHEADER hdr;
LPBITMAPINFOHEADER lpbi;

if (!hdib)
return FALSE;
CFile file;
if( !file.Open( szfile, CFile::modeCreate and CFile::modeWrite))
return FALSE;

lpbi = (LPBITMAPINFOHEADER)hdib;

int ncolors = 1 << lpbi->biBitCount;

// fill in the fields of the file header
hdr.bfType= ((WORD) ('M' << 8) and 'B');
hdr.bfSize=GlobalSize(hdib) + sizeof( hdr );
hdr.bfReserved1=0;
hdr.bfReserved2=0;
hdr.bfOffBits=(DWORD) (sizeof( hdr )+lpbi->biSize +ncolors * sizeof(RGBQUAD));
// write the file header
file.Write( &hdr, sizeof(hdr) );
// write the dib header and the bits
file.Write( lpbi, GlobalSize(hdib) );
return TRUE;
}

//以下程序演示利用上面的两个函数将一个CBitmap 对象写入文件中
CPalette pal;
CDC* dc=m_ShowPicture.GetDC();
if( dc->GetDeviceCaps(RASTERCAPS) & RC_PALETTE)
{
UINT nsize = sizeof(LOGPALETTE) + (sizeof(PALETTEENTRY) * 256);
LOGPALETTE* plp = (LOGPALETTE *) new BYTE[nsize];
plp->palVersion = 0x300;
plp->palNumEntries = GetSystemPaletteEntries(dc->m_hDC, 0, 255, plp->palPalEntry );
// create the palette
pal.CreatePalette( plp );
delete[] plp;
}
HANDLE hdib = DdbToDib(bitmap, BI_RGB, &pal );
if( hdib != NULL)
{
WriteDib(lpszFileName, hdib );
GlobalFree( hdib );
}

//以下程序演示利用上面的两个函数将一个CWnd 对象转化成位图文件写入文件中
CWnd* pWnd;
CBitmap pbitmap;
CWindowDC dc(pWnd);
CDC memdc;
CRect rect;

memdc.CreateCompatibleDC(&dc);
pWnd->GetWindowRect(rect);
pbitmap.CreateCompatibleBitmap(&dc, rect.Width(),rect.Height());

CBitmap* poldbitmap = memdc.SelectObject(&pbitmap);
memdc.BitBlt(0, 0, rect.Width(),rect.Height(), &dc, 0, 0, SRCCOPY);
CPalette pal;
if( dc.GetDeviceCaps(RASTERCAPS) & RC_PALETTE)
{
UINT nsize = sizeof(LOGPALETTE) + (sizeof(PALETTEENTRY) * 256);
LOGPALETTE* plp = (LOGPALETTE *) new BYTE[nsize];
plp->palVersion = 0x300;
plp->palNumEntries = GetSystemPaletteEntries(dc.m_hDC, 0, 255, plp->palPalEntry );
// create the palette
pal.CreatePalette( plp );
delete[] plp;
}
memdc.SelectObject(poldbitmap);
HANDLE hdib = DdbToDib(pbitmap, BI_RGB, &pal );
if( hdib != NULL)
{
WriteDib(lpszFileName, hdib );
GlobalFree( hdib );
}