how do i copy a CImage DIB to clipboard

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hi. im trying to copy a CImage to the clipboard. this is what I've got. I get a read access violation on the second memcpy (which is supposed to be copying the bits of the image). how do i copy a CImage to the clipboard?

C++

CImage tmpImage = pDoc->m_imageArray[0];

int w = tmpImage.GetWidth();
int h = tmpImage.GetHeight();
int Bpp = tmpImage.GetBPP();

BITMAPINFOHEADER bmInfohdr;
bmInfohdr.biSize = sizeof(BITMAPINFOHEADER);
bmInfohdr.biWidth = w;
bmInfohdr.biHeight = -h;
bmInfohdr.biPlanes = 1;
bmInfohdr.biBitCount = Bpp;
bmInfohdr.biCompression = BI_RGB;
bmInfohdr.biSizeImage = w*h*Bpp;
bmInfohdr.biXPelsPerMeter = 0;
bmInfohdr.biYPelsPerMeter = 0;
bmInfohdr.biClrUsed = 0;
bmInfohdr.biClrImportant = 0;

BITMAPINFO bmInfo;
bmInfo.bmiHeader = bmInfohdr;
bmInfo.bmiColors[0].rgbBlue=255;


void* pBits = tmpImage.GetBits();
HANDLE hData = ::GlobalAlloc (GMEM_MOVEABLE, sizeof(BITMAPINFO) + w * h * 3);
LPVOID pData = (LPVOID) ::GlobalLock (hData);
LPBYTE p_imagebits;
p_imagebits  = (LPBYTE)pData + sizeof(BITMAPINFO);


memcpy(pData,&bmInfo,sizeof(BITMAPINFO));


DWORD dwBytes = ((DWORD) w * Bpp) / 32;

if(((DWORD) w * Bpp) % 32) {
   dwBytes++;
}
dwBytes *= 4;

unsigned long m_dwSizeImage = dwBytes * h; // no compression


memcpy (p_imagebits, pBits, m_dwSizeImage);


::GlobalUnlock (hData);

COleDataSource* pods = new COleDataSource;
pods->CacheGlobalData (CF_DIB, hData);
pods->SetClipboard ();

Posted 15-Oct-12 10:53am

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Nelek · Answer 1 · 2012-10-15T11:37:00

Solution 1

Have you given a look to Copying a DIB to the Clipboard[^] CP-Article?
It might help you

Posted 15-Oct-12 11:37am

Nelek

Jochen Arndt · Answer 2 · 2012-10-16T04:05:00

You are calculating the correct image size (knowing that scan lines are DWORD aligned) and store it in m_dwSizeImage (may be also stored in bmInfohdr.biSizeImage). But you did not use this size when allocating the global memory. Depending on the image width, m_dwSizeImage may be greater than w * h * 3 (or it is always greater when Bpp is 32), resulting in the access violation.

There is another error with the color table / usage of BITMAPINFO:
If the DIB has no color table (Bpp > 8), you must not allocate space for it. Otherwise, the size of the color table must be calculated and allocated. The BITMAPINFO structure contains only one color entry as placeholder.

So you should move the image size calculation code on top of the allocation and use something like this (note the usage of BITMAINFOHEADER instead of BITMAPINFO):

SIZE_T dwColTableLen = (Bpp <= 8) ? (1 << Bpp) * sizeof(RGBQUAD) : 0;
HANDLE hData = ::GlobalAlloc(GMEM_MOVEABLE, 
    sizeof(BITMAPINFOHEADER) + dwColTableLen + m_dwSizeImage);
...
if (dwColTableLen)
{
    LPBYTE lpColorTable = (LPBYTE)pData + sizeof(BITMAPINFOHEADER);
    // pColors must point to the source color table
    memcpy(lpColorTable, pColors, dwColTableLen);
}
p_imagebits  = (LPBYTE)pData + sizeof(BITMAPINFOHEADER) + dwColTableLen;