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c++ & gdi+: stretch a screenshot


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for quiet some time i am occupied by this little assignment:

Take a screenshot, shrink it (while preserving the aspect ration) and save it to disk.

my code:

int GetEncoderClsid(const WCHAR* format, CLSID* pClsid)
using namespace Gdiplus;
UINT num = 0; // number of image encoders
UINT size = 0; // size of the image encoder array in bytes ImageCodecInfo* pImageCodecInfo = NULL; GetImageEncodersSize(&num, &size);
if(size == 0)
return -1; // Failure pImageCodecInfo = (ImageCodecInfo*)(GlobalAlloc(0,size));
if(pImageCodecInfo == NULL)
return -1; // Failure GetImageEncoders(num, size, pImageCodecInfo); for(UINT j = 0; j < num; ++j)
if( wcscmp(pImageCodecInfo[j].MimeType, format) == 0 )
*pClsid = pImageCodecInfo[j].Clsid;
return j; // Success
} GlobalFree(pImageCodecInfo);
return 0;
}int main()
ULONG_PTR m_gdiplusToken;
Gdiplus::GdiplusStartupInput gdiplusStartupInput;
Gdiplus::GdiplusStartup(&m_gdiplusToken, &gdiplusStartupInput, NULL);
Bitmap* bm = new Bitmap(1450,1050,PixelFormat32bppARGB);//create an empty image HDC scrn = GetDC(0);//take screenshot
Graphics gr(scrn);//assign it to a graphics object gr.DrawImage(bm,100,100,1450,1050);//shrink it to 100x100 CLSID clsid;
GetEncoderClsid(L"image/jpeg", &clsid);//get jpg encoder bm->Save(L"D:\\wtf.jpg",&clsid);//save image return 0;

obviously i am not the greatest gdi+ expert around...

but i cant see why this code just fails without any error (image is just not created....)

Edited by deepzero
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