+      theWriter->Key ("mimeType");
+      theWriter->String ("image/png");

@@ -301,8 +338,10 @@ bool RWGltf_CafWriter::Perform (const Handle(TDocStd_Document)& theDocument,
                                 const TDF_LabelSequence& theRootLabels,
                                 const TColStd_MapOfAsciiString* theLabelFilter,
                                 const TColStd_IndexedDataMapOfStringString& theFileInfo,
-                                const Message_ProgressRange& theProgress)
+                                const Message_ProgressRange& theProgress,
+                                Standard_Boolean theIsTexturesInside)

+  Standard_Boolean                              myToPutTexturesInside;

+      std::ofstream aFileOut;
+      aBinFile.write ((const char*)aBuffer->Data(), aBuffer->Size());
+      aFileOut.close();
What is the purpose for unused aFileOut?

+        OSD_OpenStream (aFileIn, aCurrImageTexture->FilePath().ToCString(), std::ios::in | std::ios::binary);
+        aBuffer = new NCollection_Buffer(NCollection_BaseAllocator::CommonBaseAllocator(), aLen);
+      aBinFile.write ((const char*)aBuffer->Data(), aBuffer->Size());


This is counter-efficient always reading entire image file into temporary buffer. The usual way is reading file by chunks of reasonable size into temporary buffer / writing into output file.	

+  Standard_Boolean myToPutTexturesInside;//!< flag to write image textures into binary gltf format (.glb)

+  void SetTexturesInside (Standard_Boolean theToPutTexturesInside) { myToPutTexturesInside = theToPutTexturesInside; }

+  myToPutTexturesInside (Standard_False)
...
+  Standard_Boolean isTexturesInside = Standard_False;

+  if (myToPutTexturesInside)

+  Standard_Integer aGltfImgBufferKey = myNbImages + 4;

   Standard_EXPORT void addImage (RWGltf_GltfOStreamWriter* theWriter,
                                  const Handle(Image_Texture)& theTexture,
-                                 Standard_Boolean& theIsStarted);
+                                 Standard_Boolean& theIsStarted,
+                                 Standard_Boolean theIsTexturesInside = Standard_False);

+      Handle(NCollection_Buffer) aBuffer = aCurrImageTexture->DataBuffer();
+      if (aBuffer.IsNull())
+      {

+        for (Standard_Size anIdx = 0; anIdx < aLen; anIdx += 16)
+          aBuffer = new NCollection_Buffer(NCollection_BaseAllocator::CommonBaseAllocator(), aCurrSize);

+          aBinFile.write ((const char*)aBuffer->Data(), aBuffer->Size());
+          if (!aBinFile.good())

   RWGltf_GltfBufferView                         myBuffViewNorm;      //!< current buffer view with nodes normals
   RWGltf_GltfBufferView                         myBuffViewTextCoord; //!< current buffer view with nodes UV coordinates
   RWGltf_GltfBufferView                         myBuffViewInd;       //!< current buffer view with triangulation indexes
+  NCollection_Vector<RWGltf_GltfBufferView>     myBuffViewImages;    //!< current buffer views with images

+    if (std::find (myImageVector.begin(), myImageVector.end(), aMetallicRoughnessTexture) == myImageVector.end())

+      std::string anImageFormat = "image/";

+      anImageFormat += theTexture->ProbeImageFileFormat().ToCString();