有几个小问题想请教一下各位大神

[shuxiong_2000]

我想从普通的USB摄像头获取一个界面然后从界面上获取某个固定的坐标点的颜色～摄像头界面在软件窗体上运行时我知道怎么做～那么有没有办法能让摄像头界面在后台运行的时候能获取到这个坐标点的颜色呢？？求各位大神帮帮忙

[脆皮大雪糕]

看你用什么方式了，如果用网上能找到的比较普遍的用剪贴板来处理，其实可以取到剪贴板的数据。 还有就是用directshow 那也是直接抓到数据了，无所谓是不是后台了

[shuxiong_2000]

引用 1 楼 脆皮大雪糕的回复:

看你用什么方式了，如果用网上能找到的比较普遍的用剪贴板来处理，其实可以取到剪贴板的数据。 还有就是用directshow 那也是直接抓到数据了，无所谓是不是后台了

那这个该怎么写呢？小弟我是初学的～很多东西都不懂啊

[赵4老师]

仅供参考，尽管不是VB6：

//GDI与DX截屏API操作
LPDIRECTDRAW        lpDD       = NULL;
LPDIRECTDRAWSURFACE lpDDSPrime = NULL;
LPDIRECTDRAWSURFACE lpDDSBack  = NULL;
LPDIRECTDRAWSURFACE lpDDSGdi   = NULL;
LPDIRECTDRAWSURFACE lpSurf     = NULL;

DDSURFACEDESC DDSdesc;
BOOL m_b24=TRUE;
//rfbServerInitMsg m_scrinfo;
RECT    m_bmrect;

struct _BMInfo {
    BITMAPINFO bmi       ;
    BOOL       truecolour;
    RGBQUAD    cmap[256] ;
} m_bminfo; // 用来保存位图信息的结构

int DX_Init() {// DirectX初始化。返回当前表面获取一张屏幕位图的存储空间大小
    HRESULT hr;

    // 初始化directX
    hr = DirectDrawCreate(0, &lpDD, 0);
    if (FAILED(hr)) return FALSE;

    hr = lpDD->SetCooperativeLevel(NULL, DDSCL_NORMAL);
    if (FAILED(hr)) return FALSE;

    ZeroMemory(&DDSdesc, sizeof(DDSdesc));
    DDSdesc.dwSize  = sizeof(DDSdesc);
    DDSdesc.dwFlags = DDSD_CAPS;
    DDSdesc.ddsCaps.dwCaps = DDSCAPS_PRIMARYSURFACE;
    hr = lpDD->CreateSurface(&DDSdesc, &lpDDSPrime, 0);
    if (FAILED(hr)) return FALSE;

    hr = lpDD->GetGDISurface(&lpDDSGdi);
    if (FAILED(hr)) return FALSE;

    ZeroMemory(&DDSdesc, sizeof(DDSdesc));
    DDSdesc.dwSize  = sizeof(DDSdesc);
    DDSdesc.dwFlags = DDSD_ALL;
    hr = lpDDSPrime->GetSurfaceDesc(&DDSdesc);
    if (FAILED(hr)) return FALSE;

    // 初始化位图信息
    if ((DDSdesc.dwFlags & DDSD_WIDTH) && (DDSdesc.dwFlags & DDSD_HEIGHT)) {
        m_bmrect.left = m_bmrect.top = 0;
        m_bmrect.right = DDSdesc.dwWidth;
        m_bmrect.bottom = DDSdesc.dwHeight;
    } else return FALSE;

    m_bminfo.bmi.bmiHeader.biCompression = BI_RGB;//BI_BITFIELDS;
    m_bminfo.bmi.bmiHeader.biBitCount = DDSdesc.ddpfPixelFormat.dwRGBBitCount;

    // m_bminfo.truecolour = DDSdesc.ddpfPixelFormat.dwFlags & DDPF_RGB;
    if (m_bminfo.bmi.bmiHeader.biBitCount > 8)
        m_bminfo.truecolour = TRUE;
    else
        m_bminfo.truecolour = FALSE;

    ZeroMemory(&DDSdesc, sizeof(DDSdesc));
    DDSdesc.dwSize = sizeof(DDSdesc);
    DDSdesc.dwFlags = DDSD_CAPS | DDSD_HEIGHT |DDSD_WIDTH;
    DDSdesc.ddsCaps.dwCaps = DDSCAPS_OFFSCREENPLAIN;
    DDSdesc.dwHeight = m_bmrect.bottom - m_bmrect.top;
    DDSdesc.dwWidth  = m_bmrect.right  - m_bmrect.left;
    hr = lpDD->CreateSurface(&DDSdesc, &lpDDSBack, 0);
    if (FAILED(hr)) return FALSE;
//  hr = lpDDSPrime->QueryInterface( IID_IDirectDrawSurface3, (LPVOID *)&lpSurf);
//  if (FAILED(hr)) return FALSE;

    switch (m_bminfo.bmi.bmiHeader.biBitCount) {
    case 32:
    case 24:
       // Update the bitmapinfo header
       m_b24 = TRUE;
       m_bminfo.bmi.bmiHeader.biSize = sizeof( BITMAPINFOHEADER );
       m_bminfo.bmi.bmiHeader.biWidth = 1024;
       m_bminfo.bmi.bmiHeader.biHeight = 768;
       m_bminfo.bmi.bmiHeader.biPlanes = 1;
//     m_bminfo.bmi.bmiHeader.biBitCount = 24;
       m_bminfo.bmi.bmiHeader.biCompression = BI_RGB;
       m_bminfo.bmi.bmiHeader.biSizeImage = abs((m_bminfo.bmi.bmiHeader.biWidth * m_bminfo.bmi.bmiHeader.biHeight * m_bminfo.bmi.bmiHeader.biBitCount)/8);
       m_bminfo.bmi.bmiHeader.biXPelsPerMeter = (1024*1000)/1024;
       m_bminfo.bmi.bmiHeader.biYPelsPerMeter = (768*1000)/768;
       m_bminfo.bmi.bmiHeader.biClrUsed   = 0;
       m_bminfo.bmi.bmiHeader.biClrImportant = 0;
       break;
    }

    return m_bminfo.bmi.bmiHeader.biSizeImage;
}

BOOL CaptureScreen(RECT &rect, BYTE *scrBuff, UINT scrBuffSize) {// 捕捉屏幕。rect: 区域。scrBuff: 输出缓冲。scrBuffSize: 缓冲区大小
    HRESULT hr=0;

    hr = lpDDSBack->BltFast(rect.left,rect.top,lpDDSPrime,&rect,DDBLTFAST_NOCOLORKEY | DDBLTFAST_WAIT);
    if (FAILED(hr)) return FALSE;

    DDSURFACEDESC surfdesc;
    ZeroMemory(&surfdesc, sizeof(surfdesc));
    surfdesc.dwSize = sizeof(surfdesc);

    hr = lpDDSBack->Lock(&rect, &surfdesc, DDLOCK_READONLY | DDLOCK_WAIT | DDLOCK_SURFACEMEMORYPTR /*|DDLOCK_NOSYSLOCK*/, NULL);
//  hr = lpDDSPrime->Lock(&rect, &surfdesc, DDLOCK_READONLY | DDLOCK_WAIT | DDLOCK_SURFACEMEMORYPTR /*|DDLOCK_NOSYSLOCK*/, NULL);
    if (FAILED(hr)) return FALSE;

    // copy the data into our buffer
    BYTE * destbuffpos, * srcbuffpos;
//  m_scrinfo.format.bitsPerPixel = 24;
    srcbuffpos = (BYTE *) surfdesc.lpSurface;
    destbuffpos = scrBuff;

    memcpy( destbuffpos, srcbuffpos,m_bminfo.bmi.bmiHeader.biSizeImage);

    // unlock the primary surface
//  lpDDSPrime->Unlock(surfdesc.lpSurface);
    lpDDSBack->Unlock(surfdesc.lpSurface);
    return TRUE;
}

int SaveBitmapToFile(BITMAP *bitmap, LPSTR lpFileName,char *lpBuf) {
   DWORD dwWritten;
   BITMAPFILEHEADER   bmfHdr;
   BITMAPINFOHEADER   bi;
   HANDLE          fh=NULL;
   bi.biSize = sizeof(BITMAPINFOHEADER);
   bi.biWidth= bitmap->bmWidth;
   bi.biHeight = bitmap->bmHeight;
   bi.biPlanes = 1;
   bi.biBitCount      = bitmap->bmBitsPixel*8;
   bi.biCompression   = BI_RGB;
   bi.biSizeImage     = 0;
   bi.biXPelsPerMeter = 0;
   bi.biYPelsPerMeter = 0;
   bi.biClrUsed       = 0;
   bi.biClrImportant  = 0;
   fh = CreateFile(lpFileName, GENERIC_WRITE, 0, NULL, CREATE_ALWAYS,FILE_ATTRIBUTE_NORMAL | FILE_FLAG_SEQUENTIAL_SCAN, NULL);
   if (fh == INVALID_HANDLE_VALUE) return FALSE;
   bmfHdr.bfType = 0x4D42; // "BM"
   bmfHdr.bfSize = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER)+bitmap->bmWidth*bitmap->bmHeight*bitmap->bmBitsPixel;
   bmfHdr.bfReserved1 = 0;
   bmfHdr.bfReserved2 = 0;
   bmfHdr.bfOffBits = (DWORD)sizeof(BITMAPFILEHEADER) + (DWORD)sizeof(BITMAPINFOHEADER);
   WriteFile(fh, (LPSTR)&bmfHdr, sizeof(BITMAPFILEHEADER), &dwWritten, NULL);
   WriteFile(fh, (char *)&bi,sizeof(BITMAPINFOHEADER), &dwWritten, NULL);
   WriteFile(fh, (char *)lpBuf,bitmap->bmWidth*bitmap->bmHeight*bitmap->bmBitsPixel, &dwWritten, NULL);
   FlushFileBuffers(fh);
   CloseHandle(fh);
   return true;
}

//(1)获取屏幕绘图设备
//(2)创建一个与屏幕绘图设备相兼容的内存绘图设备
//(2)在内存中创建一个与屏幕绘图设备相兼容的图像对象
//(3)将屏幕设备中的图像复制到内存绘图设备中
//(4)将内存图像保存到文件中
//相关函数：
//GetDIBits:按位的方式返回指定的BITMAP，并按指定的格式存储到内存中
int GetBitmapFromScreen(char *lpFileName) {
    char *lpBuf;
    HBITMAP hBitmap,hOld ;
    HDC hDC,hcDC;
    BITMAP bb;
    BITMAPINFO b;
    HANDLE hp,fh=NULL;
    DWORD dwX,dwY;

    dwX=GetSystemMetrics(SM_CXSCREEN);
    dwY=GetSystemMetrics(SM_CYSCREEN);
    hDC=GetDC(NULL);
    hcDC=CreateCompatibleDC(hDC);
    hBitmap=CreateCompatibleBitmap(hDC,dwX,dwY);
    hOld=(HBITMAP)SelectObject(hcDC,hBitmap);
    BitBlt(hcDC,0, 0,dwX,dwY, hDC, 0, 0, SRCCOPY);
    bb.bmWidth=dwX;
    bb.bmHeight =dwY;
    bb.bmPlanes = 1;
    bb.bmWidthBytes=bb.bmWidth*3;
    bb.bmBitsPixel=3;
    bb.bmType=0;
    b.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
    b.bmiHeader.biWidth        =dwX;
    b.bmiHeader.biHeight       =dwY;
    b.bmiHeader.biPlanes       =1;
    b.bmiHeader.biBitCount     =3*8;
    b.bmiHeader.biCompression  =BI_RGB;
    b.bmiHeader.biSizeImage    =0;
    b.bmiHeader.biXPelsPerMeter=0;
    b.bmiHeader.biYPelsPerMeter=0;
    b.bmiHeader.biClrUsed      =0;
    b.bmiHeader.biClrImportant =0;
    b.bmiColors[0].rgbBlue     =8;
    b.bmiColors[0].rgbGreen    =8;
    b.bmiColors[0].rgbRed      =8;
    b.bmiColors[0].rgbReserved =0;
    hp=GetProcessHeap();
    lpBuf=(char *)HeapAlloc(hp,HEAP_ZERO_MEMORY,bb.bmHeight*bb.bmWidth*4);
    GetDIBits(hcDC,hBitmap,0,dwY,lpBuf,&b,DIB_RGB_COLORS);
    SaveBitmapToFile(&bb,lpFileName,lpBuf);
    ReleaseDC(NULL,hDC);
    DeleteDC(hcDC);
    DeleteObject(hBitmap);
    DeleteObject(hOld);
    HeapFree(hp,0,lpBuf);
    return true;
}