graphicfilter: store the funky animated GIF in a PNG as a GIF

MS had a really bad idea to store an animated GIF inside a PNG for
some reason. This situation was handled correctly in LO but we
still pretended that this was a PNG file, which was causing
confusion for some users that wanted to extract the image from
the document. With this change we extract the animated GIF from
the PNG and store just the GIF in the document.

Change-Id: I4c70d118e8decd7aa1b108b6b1d725301904a35b

vcl/source/filter/graphicfilter.cxx

@@ -1455,21 +1455,28 @@ sal_uInt16 GraphicFilter::ImportGraphic( Graphic& rGraphic, const OUString& rPat
             else
             {
                 // check if this PNG contains a GIF chunk!
-                const std::vector< vcl::PNGReader::ChunkData >&    rChunkData = aPNGReader.GetChunks();
-                std::vector< vcl::PNGReader::ChunkData >::const_iterator aIter( rChunkData.begin() );
-                std::vector< vcl::PNGReader::ChunkData >::const_iterator aEnd ( rChunkData.end() );
-                while( aIter != aEnd )
+                const std::vector<vcl::PNGReader::ChunkData>& rChunkData = aPNGReader.GetChunks();
+                std::vector<vcl::PNGReader::ChunkData>::const_iterator aIter(rChunkData.begin());
+                std::vector<vcl::PNGReader::ChunkData>::const_iterator aEnd(rChunkData.end());
+
+                while (aIter != aEnd)
                 {
                     // Microsoft Office is storing Animated GIFs in following chunk
-                    if ( aIter->nType == PMGCHUNG_msOG )
+                    if (aIter->nType == PMGCHUNG_msOG)
                     {
                         sal_uInt32 nChunkSize = aIter->aData.size();
-                        if ( nChunkSize > 11 )
+
+                        if (nChunkSize > 11)
                         {
-                            const std::vector< sal_uInt8 >& rData = aIter->aData;
-                            SvMemoryStream aIStrm( (void*)&rData[ 11 ], nChunkSize - 11, StreamMode::READ );
-                            ImportGIF( aIStrm, rGraphic );
-                            eLinkType = GFX_LINK_TYPE_NATIVE_PNG;
+                            const std::vector<sal_uInt8>& rData = aIter->aData;
+                            nGraphicContentSize = nChunkSize - 11;
+                            SvMemoryStream aIStrm(const_cast<sal_uInt8*>(&rData[11]), nGraphicContentSize, StreamMode::READ);
+                            pGraphicContent = new sal_uInt8[nGraphicContentSize];
+                            sal_uInt64 aCurrentPosition = aIStrm.Tell();
+                            aIStrm.Read(pGraphicContent, nGraphicContentSize);
+                            aIStrm.Seek(aCurrentPosition);
+                            ImportGIF(aIStrm, rGraphic);
+                            eLinkType = GFX_LINK_TYPE_NATIVE_GIF;
                             break;
                         }
                     }
@@ -1520,6 +1527,7 @@ sal_uInt16 GraphicFilter::ImportGraphic( Graphic& rGraphic, const OUString& rPat
                 rIStream.Seek(nStreamPosition);
                 rIStream.Read(&aTwoBytes[0], 2);
                 rIStream.Seek(nStreamPosition);
+
                 if(aTwoBytes[0] == 0x1F && aTwoBytes[1] == 0x8B)
                 {
                     SvMemoryStream aMemStream;