windows API 实现截图

參考：http://bbs.csdn.net/topics/330154355

#include "stdio.h"
#include "windows.h"
/************************************************************************/
/* hBitmap    为刚才的屏幕位图句柄
/* lpFileName 为须要保存的位图文件名称
/************************************************************************/
int SaveBitmapToFile(HBITMAP hBitmap,LPSTR lpFileName)
{
    HDC            hDC; //设备描写叙述表
    int            iBits;//当前显示分辨率下每一个像素所占字节数
    WORD           wBitCount;//位图中每一个像素所占字节数
    DWORD          dwPaletteSize=0;//定义调色板大小
    DWORD          dwBmBitsSize;//位图中像素字节大小
    DWORD          dwDIBSize;// 位图文件大小
    DWORD          dwWritten;//写入文件字节数
    BITMAP         Bitmap;//位图结构
    BITMAPFILEHEADER   bmfHdr;   //位图属性结构
    BITMAPINFOHEADER   bi;       //位图文件头结构
    LPBITMAPINFOHEADER lpbi;     //位图信息头结构     指向位图信息头结构
    HANDLE          fh;//定义文件句柄
    HANDLE            hDib;//分配内存句柄
    HANDLE            hPal;//分配内存句柄
    HANDLE          hOldPal=NULL;//调色板句柄  

    //计算位图文件每一个像素所占字节数
    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 if (iBits <= 24)
        wBitCount = 24;
    else if (iBits<=32)
        wBitCount = 24;

    //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);
    if (lpbi==NULL)
    {
        return 0;
    }

    *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 1;
}

HBITMAP   GetCaptureBmp()
{
    HDC     hDC;
    HDC     MemDC;
    BYTE*   Data;
    HBITMAP   hBmp;
    BITMAPINFO   bi;   

    memset(&bi,   0,   sizeof(bi));
    bi.bmiHeader.biSize   =   sizeof(BITMAPINFO);
    bi.bmiHeader.biWidth   =  GetSystemMetrics(SM_CXSCREEN);
    bi.bmiHeader.biHeight   = GetSystemMetrics(SM_CYSCREEN);
    bi.bmiHeader.biPlanes   =   1;
    bi.bmiHeader.biBitCount   =   24;   

    hDC   =   GetDC(NULL);
    MemDC   =   CreateCompatibleDC(hDC);
    hBmp   =   CreateDIBSection(MemDC,   &bi, DIB_RGB_COLORS,   (void**)&Data,   NULL,   0);
    SelectObject(MemDC,   hBmp);
    BitBlt(MemDC,   0,   0,   bi.bmiHeader.biWidth,   bi.bmiHeader.biHeight,hDC,   0,   0,   SRCCOPY);
    ReleaseDC(NULL,   hDC);
    DeleteDC(MemDC);
    return   hBmp;
}   

void main()
{
    HBITMAP   hBmp;
    hBmp   =   GetCaptureBmp();
    SaveBitmapToFile(hBmp,"c:\\11.bmp");
}