[英]Creating a HBITMAP from glReadPixels
我需要根據glReadPixels()調用返回的數據創建一個HBITMAP:
HDC hCompDC = CreateCompatibleDC(NULL);
HDC hDC = GetDC();
m_hClipboardBitmap = CreateCompatibleBitmap(hDC, size.cx, size.cy);
if ( m_hClipboardBitmap == NULL )
{
throw runtime_error( "Unable to create bitmap." );
}
HBITMAP hOldBm = (HBITMAP) SelectObject( hCompDC, m_hClipboardBitmap );
int numberOfBytes = 4 * size.cx * size.cy;
unsigned char *pPixelData = new unsigned char[numberOfBytes];
::glReadPixels(minimum.x, minimum.y, size.cx, size.cy, GL_BGRA, GL_UNSIGNED_BYTE, pPixelData);
我嘗試使用:
BITMAPINFOHEADER header;
header.biWidth = size.cx;
header.biHeight = size.cy;
header.biSizeImage = numberOfBytes;
header.biSize = sizeof(BITMAPINFOHEADER);
header.biPlanes = 1;
header.biBitCount = 4 * 8; // RGBA
header.biCompression = 0;
header.biXPelsPerMeter = 0;
header.biYPelsPerMeter = 0;
header.biClrUsed = 0;
header.biClrImportant = 0;
HANDLE handle = (HANDLE)::GlobalAlloc (GHND, sizeof(BITMAPINFOHEADER) + numberOfBytes);
if(handle != NULL)
{
char *pData = (char *) ::GlobalLock((HGLOBAL)handle);
memcpy(pData,&header,sizeof(BITMAPINFOHEADER));
memcpy(pData + sizeof(BITMAPINFOHEADER), pPixelData, numberOfBytes);
::GlobalUnlock((HGLOBAL)handle);
OpenClipboard();
EmptyClipboard();
SetClipboardData(CF_DIB, handle);
CloseClipboard();
}
然后將其粘貼到mspaint OK(這樣數據就很好了),但是到底如何將它放入HBITMAP中呢?!?!
線程很舊,但是我想給出一個答案,至少要保留它作為存儲庫。
void WriteOpenGLPixelsToHBITMAP( HBITMAP dstHBITMAP, HDC dstDC, SIZE dims )
{
BITMAPINFO bitmapInfo;
{
::memset( &bitmapInfo, 0, sizeof( BITMAPINFO ) );
bitmapInfo.bmiHeader.biSize = sizeof( BITMAPINFOHEADER );
bitmapInfo.bmiHeader.biPlanes = 1;
bitmapInfo.bmiHeader.biBitCount = 32;
bitmapInfo.bmiHeader.biCompression = BI_RGB;
bitmapInfo.bmiHeader.biWidth = dims.cx;
bitmapInfo.bmiHeader.biHeight = dims.cy;
bitmapInfo.bmiHeader.biSizeImage = dims.cx * dims.cy * 4; // Size 4, assuming RGBA from OpenGL
}
void *bmBits = NULL;
HDC memDC = ::CreateCompatibleDC( dstDC );
HBITMAP memBM = ::CreateDIBSection( NULL, &bitmapInfo, DIB_RGB_COLORS, &bmBits, NULL, 0 );
::glReadPixels( 0,
0,
dims.cx,
dims.cy,
GL_BGRA_EXT,
GL_UNSIGNED_BYTE,
bmBits );
HGDIOBJ prevBitmap = ::SelectObject( memDC, memBM );
HGDIOBJ obj = ::SelectObject( dstDC, dstHBITMAP );
// Remember that OpenGL origin is at bottom, left, but bitmaps are top, left
if ( false == BitBlt( dstDC, 0 /*left*/, dims.cy /*top*/, dims.cx, dims.cy, memDC, 0, 0, SRCCOPY ) )
{
assert( false && "Failed to write pixels to HBitmap from OpenGL glReadPixels" );
}
::SelectObject( memDC, prevBitmap );
::DeleteObject( memBM );
::DeleteDC( memDC );
}
如前所述,請注意圖像被反轉了。 您可以將SRCCOPY交換為SRCINVERT。 另外,您可能要確保要復制區域。 上面的代碼假定該區域與視口匹配。
您在調用帶有正確參數的函數嗎? 檢查該功能的文檔: http : //msdn.microsoft.com/zh-cn/library/dd183491(v=vs.85).aspx 。 似乎您已經交換了參數順序,並正在將指針傳遞給指向數據的指針。
-提摩
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