缩放图片并保存

IStream* CpictureDemoDlg::StretchPic(const WCHAR *path,const WCHAR* format, int width, int heigh)
{
    Bitmap orgpic(path) ;
	Image *Despic = orgpic.GetThumbnailImage(width,heigh) ;

    IStream* pstm = NULL; 

	CLSID encoderClsid ;
	GetEncoderClsid(format,&encoderClsid) ;
	Status sta =Despic->Save(TEXT("d:\\2.bmp"),&encoderClsid,0) ; //Despic->Save(pstm, &encoderClsid,0);
	if (sta == Ok)
	{
		return pstm ;
	}
	return NULL ;
}

int CpictureDemoDlg::GetEncoderClsid(const WCHAR* format, CLSID* pClsid)
{
	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*)(malloc(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;
			free(pImageCodecInfo);
			return j; // Success
		}
	}
	free(pImageCodecInfo);
	return -1; 
}