从glReadPixels创建HBITMAP

问题描述

我需要根据glReadPixels()调用返回的数据创建一个HBITMAP:

I need to create a HBITMAP from data returned by a glReadPixels() call:

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);

我尝试使用:

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();
}

然后将其粘贴到mspaint中就可以了(所以数据很好)，但是到底如何将其放入HBITMAP中呢?！?！

And that pastes into mspaint OK (so the data is good) but how on earth do I get it into a HBITMAP?!?!

推荐答案

非常老的线程，但我想给出一个答案，至少要将其保留为存储库.

Very old thread, but I wanted to give an answer, at least to keep it as a repository.

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，请注意图像被反转了.您可以将SRCCOPY交换为SRCINVERT.另外，您可能要确保要复制区域.上面的代码假定该区域与视口匹配.

As mentioned, be aware of image being inverted. You can swap SRCCOPY for SRCINVERT. Also you might want to make sure you are copying regions. The code above assumes that the region matches the viewport.

这篇关于从glReadPixels创建HBITMAP的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！