为什么显示的图象上下反转了？

cyberkit 2006-07-10 04:54:31

代码如下：

// TODO: Add extra validation here
HBITMAP hOldBitmap, hbmScreen;

HDC hdcScreen = CreateDC("DISPLAY", NULL, NULL, NULL);
HDC hdcCompatible = CreateCompatibleDC(hdcScreen);

// Create a compatible bitmap for hdcScreen.

hbmScreen = CreateCompatibleBitmap(hdcScreen,
GetDeviceCaps(hdcScreen, HORZRES),
GetDeviceCaps(hdcScreen, VERTRES));

if (hbmScreen == 0)
{
AfxMessageBox("hbmScreen");
return;
}

// Select the bitmaps into the compatible DC.
hOldBitmap =(HBITMAP)SelectObject(hdcCompatible, hbmScreen);

if (!hOldBitmap)
{
AfxMessageBox("Compatible Bitmap Selection");
return;
}

//Copy color data for the entire display into a
//bitmap that is selected into a compatible DC.

if (!BitBlt(hdcCompatible,
0,0,
GetDeviceCaps(hdcScreen, HORZRES), GetDeviceCaps(hdcScreen, VERTRES),
hdcScreen,
0,0,
SRCCOPY))
{
AfxMessageBox("Screen to Compat Blt Failed");
return;
}

hbmScreen = (HBITMAP) SelectObject(hdcCompatible, hOldBitmap);
//==================================================================

BITMAP bmp;
PBITMAPINFO pbmi;
WORD BitsPerPixel;

// Retrieve the bitmap color format, width, and height.
//根据位图句柄获取位图信息
if (!GetObject(hbmScreen, sizeof(BITMAP), (LPSTR)&bmp))
{
AfxMessageBox("GetObject");
return;
}

// Convert the color format to a count of bits.
BitsPerPixel = (WORD)(bmp.bmPlanes * bmp.bmBitsPixel);
if (BitsPerPixel == 1)
BitsPerPixel = 1;
else if (BitsPerPixel <= 4)
BitsPerPixel = 4;
else if (BitsPerPixel <= 8)
BitsPerPixel = 8;
else if (BitsPerPixel <= 16)
BitsPerPixel = 16;
else if (BitsPerPixel <= 24)
BitsPerPixel = 24;
else BitsPerPixel = 32;

// Allocate memory for the BITMAPINFO structure. (This structure
// contains a BITMAPINFOHEADER structure and an array of RGBQUAD
// data structures.)

if (BitsPerPixel != 24)
pbmi = (PBITMAPINFO) LocalAlloc(LPTR,
sizeof(BITMAPINFOHEADER) +
sizeof(RGBQUAD) * (1<< BitsPerPixel));

// There is no RGBQUAD array for the 24-bit-per-pixel format.

else
pbmi = (PBITMAPINFO) LocalAlloc(LPTR,
sizeof(BITMAPINFOHEADER));

// Initialize the fields in the BITMAPINFO structure.

pbmi->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
pbmi->bmiHeader.biWidth = bmp.bmWidth;
pbmi->bmiHeader.biHeight = bmp.bmHeight;
pbmi->bmiHeader.biPlanes = bmp.bmPlanes;
pbmi->bmiHeader.biBitCount = bmp.bmBitsPixel;
if (BitsPerPixel < 24)
pbmi->bmiHeader.biClrUsed = (1<<BitsPerPixel);

// If the bitmap is not compressed, set the BI_RGB flag.
pbmi->bmiHeader.biCompression = BI_RGB;

// Compute the number of bytes in the array of color
// indices and store the result in biSizeImage.
// For Windows NT, the width must be DWORD aligned unless
// the bitmap is RLE compressed. This example shows this.
// For Windows 95/98/Me, the width must be WORD aligned unless the
// bitmap is RLE compressed.
pbmi->bmiHeader.biSizeImage = ((pbmi->bmiHeader.biWidth * BitsPerPixel +31) & ~31) /8 * pbmi->bmiHeader.biHeight;
// Set biClrImportant to 0, indicating that all of the
// device colors are important.
pbmi->bmiHeader.biClrImportant = 0;

//===================================================================
PBITMAPINFOHEADER pbih = (PBITMAPINFOHEADER) pbmi;

LPBYTE lpBits = (LPBYTE) GlobalAlloc(GMEM_FIXED, pbih->biSizeImage);
if (!GetDIBits(hdcCompatible, hbmScreen, 0, pbih->biHeight, lpBits, pbmi,
DIB_RGB_COLORS))
{
AfxMessageBox("GetDIBits");
return;
}

DWORD ErrCode = ::GetLastError();
if (ErrCode != 0)
{
CString ErrString;
ErrString.Format("%d", ErrCode);
AfxMessageBox(ErrString);
}

HBITMAP hBitmap = ::CreateBitmap(pbih->biWidth, pbih->biHeight, pbih->biPlanes, pbih->biBitCount, lpBits);
CDC *pDC = GetDC();
pDC->DrawState(CPoint(0,0), CSize(400,300), hBitmap, DST_BITMAP);

ReleaseDC(pDC);
DeleteDC(hdcScreen);
DeleteDC(hdcCompatible);

::DeleteObject(hOldBitmap);
::DeleteObject(hbmScreen);
::DeleteObject(hBitmap);
GlobalFree((HGLOBAL)lpBits);

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