使用GDI+保存带品质的JPG

    由于使用CImage将图像转换成JPG后品质严重受损，如果使用第三方库程序体积会很大，所以使用GDI+是最合适的选择。下面的代码示例了将位图格式的图像转换成不同品质的JPG格式，注意在使用之前要初始化GDI+库。

 

 HRESULT SaveImage(BITMAPINFO *pbi, void *pBits, LPCTSTR pszFileName, LONG lQuality){ASSERT(pbi!=NULL && pBits!=NULL);ASSERT(pszFileName!=NULL);if (pbi==NULL || pBits==NULL || pszFileName==NULL)return E_FAIL;GUID guidImageFormat=Gdiplus::ImageFormatJPEG;Gdiplus::EncoderParameters eps;eps.Count=1;eps.Parameter[0].Guid=Gdiplus::EncoderQuality;eps.Parameter[0].NumberOfValues=1;eps.Parameter[0].Type=Gdiplus::EncoderParameterValueTypeLong;eps.Parameter[0].Value=&lQuality;UINT nEncoders;UINT nBytes;Gdiplus::Status status;status = Gdiplus::GetImageEncodersSize( &nEncoders, &nBytes );if( status != Gdiplus::Ok ){return (E_FAIL);}USES_CONVERSION_EX;Gdiplus::ImageCodecInfo* pEncoders = static_cast< Gdiplus::ImageCodecInfo* >( _ATL_SAFE_ALLOCA(nBytes, _ATL_SAFE_ALLOCA_DEF_THRESHOLD) );status = Gdiplus::GetImageEncoders( nEncoders, nBytes, pEncoders );if( status != Gdiplus::Ok ){return( E_FAIL );}CLSID clsidEncoder = CLSID_NULL;// Determine clsid from file typefor (UINT iCodec = 0; iCodec < nEncoders; iCodec++){if (pEncoders[iCodec].FormatID==guidImageFormat){clsidEncoder=pEncoders[iCodec].Clsid;break;}}if( clsidEncoder == CLSID_NULL ){return( E_FAIL );}LPCWSTR pwszFileName = T2CW_EX( pszFileName, _ATL_SAFE_ALLOCA_DEF_THRESHOLD );Gdiplus::Bitmap bm(pbi,pBits);status = bm.Save( pwszFileName, &clsidEncoder, &eps );if( status != Gdiplus::Ok ){return( E_FAIL );}return S_OK;}