截取屏幕指定区域保存为BMP文件

HBITMAP CopyScreenToBitmap(LPRECT lpRect)
{
//屏幕和内存设备描述表
HDC hSrcDC, hMemDC;
//位图句柄
HBITMAP hBitmap, hOldBitmap;
//选定区域坐标
int nX, nY, nX2, nY2;
//位图宽度和高度
int nWidth, nHeight;
//屏幕分辨率
int xScrn, yScrn;

//确保选定区域不为空矩形
if(IsRectEmpty(lpRect))
return NULL;
//为屏幕创建设备描述表
hSrcDC = CreateDC("DISPLAY", NULL, NULL, NULL);
//为屏幕设备描述表创建兼容的内存设备描述表
hMemDC = CreateCompatibleDC(hSrcDC);
//获得选定区域坐标
nX ＝ lpRect->left;
nY = lpRect->top;
nX2 = lpRect->right;
nY2 = lpRect->bottom;
//获得屏幕分辨率
xScrn = GetDeviceCaps(hSrcDC, HORZRES);
yScrn = GetDeviceCaps(hSrcDC, VERTRES);
//确保选定区域是可见的
if(nX<0)
nX = 0;
if(nY<0)
nY = 0;
if(nX2>xScrn)
nX2 = xScrn;
if(nY2>yScrn)
nY2 = yScrn;
nWidth = nX2 - nX;
nHeight = nY2 - nY;
//创建一个与屏幕设备描述表兼容的位图
hBitmap = CreateCompatibleBitmap(hSrcDC, nWidth, nHeight);
//把新位图选到内存设备描述表中
hOldBitmap = (HBITMAP)SelectObject(hMemDC, hBitmap);
//把屏幕设备描述表拷贝到内存设备描述表中
BitBlt(hMemDC, 0, 0, nWidth, nHeight, hSrcDC, nX, nY, SRCCOPY);
//得到屏幕位图的句柄
hBitmap = (HBITMAP)SelectObject(hMemDC, hOldBitmap);
//清除
DeleteDC(hSrcDC);
DeleteDC(hMemDC);
//返回位置句柄
}
*/
HBITMAP CopyScreenToBitmap(int x1, int x2, int y1, int y2)
{
//屏幕和内存设备描述表
HDC hSrcDC, hMemDC;
//位图句柄
HBITMAP hBitmap, hOldBitmap;
//选定区域坐标
int nX, nY, nX2, nY2;
//位图宽度和高度
int nWidth, nHeight;
//屏幕分辨率
int xScrn, yScrn;
/*
//确保选定区域不为空矩形
if(IsRectEmpty(lpRect))
return NULL;*/
//为屏幕创建设备描述表
hSrcDC = CreateDC("DISPLAY", NULL, NULL, NULL);
//为屏幕设备描述表创建兼容的内存设备描述表
hMemDC = CreateCompatibleDC(hSrcDC);
//获得选定区域坐标
nX = x1;
nY = y1;
nX2 = x2;
nY2 = y2;
//获得屏幕分辨率
xScrn = GetDeviceCaps(hSrcDC, HORZRES);
yScrn = GetDeviceCaps(hSrcDC, VERTRES);
//确保选定区域是可见的
if(nX<0)
nX = 0;
if(nY<0)
nY = 0;
if(nX2>xScrn)
nX2 = xScrn;
if(nY2>yScrn)
nY2 = yScrn;
nWidth = nX2 - nX;
nHeight = nY2 - nY;
//创建一个与屏幕设备描述表兼容的位图
hBitmap = CreateCompatibleBitmap(hSrcDC, nWidth, nHeight);
//把新位图选到内存设备描述表中
hOldBitmap = (HBITMAP)SelectObject(hMemDC, hBitmap);
//把屏幕设备描述表拷贝到内存设备描述表中
BitBlt(hMemDC, 0, 0, nWidth, nHeight, hSrcDC, nX, nY, SRCCOPY);
//得到屏幕位图的句柄
hBitmap = (HBITMAP)SelectObject(hMemDC, hOldBitmap);
//清除
DeleteDC(hSrcDC);
DeleteDC(hMemDC);
//返回位置句柄
return hBitmap;
}

BOOL SaveCapturedBitmap(HBITMAP hBitmap, CString FileName)
{
if(hBitmap==NULL || FileName.IsEmpty())
{
AfxMessageBox("参数错误");
return false;
}

HDC hDC;
//当前分辨率下每象素所占字节数
int iBits;
//位图中每象素所占字节数
WORD wBitCount;
//定义调色板大小， 位图中像素字节大小 ，位图文件大小 ， 写入文件字节数
DWORD dwPaletteSize=0, dwBmBitsSize=0, dwDIBSize=0, dwWritten=0;
//位图属性结构
BITMAP Bitmap;
//位图文件头结构
BITMAPFILEHEADER bmfHdr;
//位图信息头结构
BITMAPINFOHEADER bi;
//指向位图信息头结构
LPBITMAPINFOHEADER lpbi;
//定义文件，分配内存句柄，调色板句柄
HANDLE fh, hDib, hPal,hOldPal=NULL;

//计算位图文件每个像素所占字节数
hDC = CreateDC("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      wBitCount = 24;

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.biClrImportant = 0;
bi.biClrUsed = 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, (BITMAPINFO *)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(FileName, 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;
}

int main()
{
HBITMAP hCaptureBitmap = CopyScreenToBitmap(100, 700, 100, 700);
SaveCapturedBitmap(hCaptureBitmap, "Hello.bmp");
return 0;
}