场景:

1. 在做图片处理时，比如放大后或加特效后需要保存CBitmap(HBITMAP)到文件.

2.截取屏幕内容到文件时.

3.不需要加入第3方库时.

说明: 这段代码部分来自网上，第一次学atl/wtl，gdi不是很熟悉，以后转换为wtl版本吧。当然wtl项目直接用也没问题. 现在想想wxWidgets的wxImage类对这类操作方便多了。只需要调用一个SaveFile方法。

保存HBITMAP到文件:

static bool SaveBitmapToFile(CBitmap& bitmap, LPWSTR lpFileName)
{            
	HBITMAP hBitmap;	// 为刚才的屏幕位图句柄
	HDC hDC; //设备描述表  
	int iBits; //当前显示分辨率下每个像素所占字节数  
	WORD wBitCount; //位图中每个像素所占字节数	
	DWORD dwPaletteSize = 0, //定义调色板大小
		dwBmBitsSize,  //位图中像素字节大小   
		dwDIBSize,	 //位图文件大小
		dwWritten;  //写入文件字节数
	BITMAP Bitmap; //位图属性结构  
	BITMAPFILEHEADER bmfHdr; //位图文件头结构  
	BITMAPINFOHEADER bi; //位图信息头结构    
	LPBITMAPINFOHEADER lpbi; //指向位图信息头结构  
	HANDLE fh,	 //定义文件
		hDib,	 //分配内存句柄
		hPal,	//调色板句柄
		hOldPal = NULL;
	
	//计算位图文件每个像素所占字节数  
	hBitmap = bitmap;  
	hDC = CreateDC(L"DISPLAY",NULL,NULL,NULL);  
	iBits =	GetDeviceCaps(hDC, BITSPIXEL) * GetDeviceCaps(hDC, PLANES);  
	DeleteDC(hDC);
	
	if (iBits <= 1)  
		wBitCount =	1;	
	else if	(iBits <= 4)  
		wBitCount =	4;	
	else if (iBits <= 8)  
		wBitCount =	8;	
	else if	(iBits <= 24)  
		wBitCount =	24;  
	else if (iBits <= 32)
		wBitCount = 32;
	
	//计算调色板大小  
	if (wBitCount <= 8)  
		dwPaletteSize =	(1 << wBitCount) * sizeof (RGBQUAD);
	
	//设置位图信息头结构  
	GetObject(hBitmap, sizeof (BITMAP), (LPSTR)&Bitmap);
	bi.biSize = sizeof (BITMAPINFOHEADER);  
	bi.biWidth = Bitmap.bmWidth;  
	bi.biHeight = Bitmap.bmHeight;  
	bi.biPlanes = 1;	
	bi.biBitCount =	wBitCount;	
	bi.biCompression = BI_RGB;  
	bi.biSizeImage = 0;  
	bi.biXPelsPerMeter = 0;  
	bi.biYPelsPerMeter = 0;  
	bi.biClrUsed = 0;  
	bi.biClrImportant = 0;  
	
	dwBmBitsSize = ((Bitmap.bmWidth * wBitCount+31) / 32) * 4 * Bitmap.bmHeight;  
	
	//为位图内容分配内存  
	hDib = GlobalAlloc(GHND, dwBmBitsSize + dwPaletteSize + sizeof (BITMAPINFOHEADER));  
	lpbi = (LPBITMAPINFOHEADER)GlobalLock(hDib);  
	*lpbi =	bi;
	
	// 处理调色板 	   
	hPal = GetStockObject(DEFAULT_PALETTE);  
	if (hPal)  
	{  
		hDC = ::GetDC(NULL);	
		hOldPal = ::SelectPalette(hDC, (HPALETTE)hPal, FALSE);	
		RealizePalette(hDC);
	}  
	
	//	 获取该调色板下新的像素值  
	GetDIBits(hDC, hBitmap,	0, (UINT) Bitmap.bmHeight,	
		(LPSTR)lpbi + sizeof (BITMAPINFOHEADER)	+ dwPaletteSize,
		(LPBITMAPINFO)lpbi,	DIB_RGB_COLORS);  
	
	//恢复调色板		
	if (hOldPal)	
	{  
		SelectPalette(hDC, (HPALETTE)hOldPal, TRUE);  
		RealizePalette(hDC);  
		::ReleaseDC(NULL, hDC);
	}  
	
	//创建位图文件			
	fh = CreateFile(lpFileName, GENERIC_WRITE,
		0, NULL, CREATE_ALWAYS,
		FILE_ATTRIBUTE_NORMAL |	FILE_FLAG_SEQUENTIAL_SCAN, NULL);  
	
	if (fh == INVALID_HANDLE_VALUE)
		return FALSE;  
	
	//	 设置位图文件头  
	bmfHdr.bfType =	0x4D42; 	//	 "BM"  
	dwDIBSize = sizeof (BITMAPFILEHEADER)	  
		+ sizeof (BITMAPINFOHEADER)  
		+ dwPaletteSize	+ dwBmBitsSize;	   
	bmfHdr.bfSize =	dwDIBSize;	
	bmfHdr.bfReserved1 = 0;  
	bmfHdr.bfReserved2 = 0;  
	bmfHdr.bfOffBits = (DWORD)sizeof (BITMAPFILEHEADER)	  
		+ (DWORD)sizeof (BITMAPINFOHEADER)  
		+ dwPaletteSize;	
	
	//	 写入位图文件头  
	WriteFile(fh, (LPSTR)&bmfHdr, sizeof(BITMAPFILEHEADER), &dwWritten,	NULL);	
	
	//	 写入位图文件其余内容  
	WriteFile(fh, (LPSTR)lpbi, dwDIBSize,
		&dwWritten, NULL);
	
	//清除		  
	GlobalUnlock(hDib);  
	GlobalFree(hDib);  
	CloseHandle(fh);  

	return TRUE;	
}  

保存屏幕到文件:

static void SaveScreenToFile(LPCTSTR szFileName)
{
	HDC hScrDC = ::GetDC(NULL);
	HDC hMemDC = NULL;

	BYTE *lpBitmapBits = NULL; 

	int nWidth = GetSystemMetrics(SM_CXSCREEN);
	int nHeight = GetSystemMetrics(SM_CYSCREEN); 

	hMemDC = ::CreateCompatibleDC(hScrDC); 

	BITMAPINFO bi; 
	ZeroMemory(&bi, sizeof(BITMAPINFO));
	bi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
	bi.bmiHeader.biWidth = nWidth;
	bi.bmiHeader.biHeight = nHeight;
	bi.bmiHeader.biPlanes = 1;
	bi.bmiHeader.biBitCount = 24;

	HBITMAP bitmap = ::CreateDIBSection(hMemDC, &bi, DIB_RGB_COLORS, (LPVOID*)&lpBitmapBits, NULL, 0);
	HGDIOBJ oldbmp = ::SelectObject(hMemDC, bitmap); 

	::BitBlt(hMemDC, 0, 0, nWidth, nHeight, hScrDC, 0, 0, SRCCOPY);

	BITMAPFILEHEADER bh;
	ZeroMemory(&bh, sizeof(BITMAPFILEHEADER));
	bh.bfType = 0x4d42; //bitmap 
	bh.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
	bh.bfSize = bh.bfOffBits + ((nWidth*nHeight)*3);

	FILE* file = _wfopen(szFileName,L"wb");
	if(file)
	{ 
		fwrite(&bh,1,sizeof(BITMAPFILEHEADER),file);
		fwrite(&(bi.bmiHeader),1,sizeof(BITMAPINFOHEADER),file);
		fwrite(lpBitmapBits,1,3 * nWidth * nHeight,file);
		fclose(file);
	}

	::SelectObject(hMemDC, oldbmp);
	::DeleteObject(bitmap);
	::DeleteObject(hMemDC);
	::ReleaseDC(NULL, hScrDC);
}

[ATL/WTL]_[保存CBitmap到文件-保存屏幕内容到文件]