evc截图函数

//////////////////////////////////////////////////////////////////////////
/*
    函数: OnScreenSave
    参数: filename为存储图片的路径
 功能: 屏幕截图并保存到所指目录下
*/
//////////////////////////////////////////////////////////////////////////
void OnScreenSave(const char *filename)
{
  HDC hScrDC, hMemDC;
  int width, height;

  //the pointer will save all pixel point's color value
  BYTE *lpBitmapBits = NULL;

  //creates a device context for the screen device
  hScrDC = CreateDC(TEXT("DISPLAY"), NULL, NULL, NULL);

  //get the screen point size
  width = GetDeviceCaps(hScrDC, HORZRES);
  height = GetDeviceCaps(hScrDC, VERTRES);

  //creates a memory device context (DC) compatible with the screen device(hScrDC)
  hMemDC = CreateCompatibleDC(hScrDC);

  //initialise the struct BITMAPINFO for the bimap infomation，
  //in order to use the function CreateDIBSection
  // on wince os, each pixel stored by 24 bits(biBitCount=24)
  //and no compressing(biCompression=0)
  BITMAPINFO RGB24BitsBITMAPINFO;
  ZeroMemory(&RGB24BitsBITMAPINFO, sizeof(BITMAPINFO));
  RGB24BitsBITMAPINFO.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
  RGB24BitsBITMAPINFO.bmiHeader.biWidth = width;
  RGB24BitsBITMAPINFO.bmiHeader.biHeight = height;
  RGB24BitsBITMAPINFO.bmiHeader.biPlanes = 1;
  RGB24BitsBITMAPINFO.bmiHeader.biBitCount = 24;

  //use the function CreateDIBSection and SelectObject
  //in order to get the bimap pointer : lpBitmapBits
  HBITMAP directBmp = CreateDIBSection(hMemDC, (BITMAPINFO*)&RGB24BitsBITMAPINFO,
      DIB_RGB_COLORS, (void **)&lpBitmapBits, NULL, 0);
  HGDIOBJ previousObject = SelectObject(hMemDC, directBmp);

  // copy the screen dc to the memory dc
  BitBlt(hMemDC, 0, 0, width, height,hScrDC, 0, 0, SRCCOPY);

  //if you only want to get the every pixel color value,
  //you can begin here and the following part of this function will be unuseful;
  //the following part is in order to write file;

  //bimap file header in order to write bmp file
  BITMAPFILEHEADER bmBITMAPFILEHEADER;
  ZeroMemory(&bmBITMAPFILEHEADER, sizeof(BITMAPFILEHEADER));
  bmBITMAPFILEHEADER.bfType = 0x4d42; //bmp
  bmBITMAPFILEHEADER.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
  bmBITMAPFILEHEADER.bfSize = bmBITMAPFILEHEADER.bfOffBits + ((width*height)*3); ///3=(24 / 8)

  //write into file
  FILE *mStream = NULL;
  if((mStream = fopen(filename, "wb")))
  {
    //write bitmap file header
    fwrite(&bmBITMAPFILEHEADER, sizeof(BITMAPFILEHEADER), 1, mStream);
    //write bitmap info
    fwrite(&(RGB24BitsBITMAPINFO.bmiHeader), sizeof(BITMAPINFOHEADER), 1, mStream);
    //write bitmap pixels data
    fwrite(lpBitmapBits, 3*width*height, 1, mStream);
    //close file
    fclose(mStream);
  }

  //delete
  DeleteObject(hMemDC);
  DeleteObject(hScrDC);
  DeleteObject(directBmp);
  DeleteObject(previousObject);
}