iewic.pas:

procedure ConvertWICBitmapToIEBitmap(wicFactory: IE_IWICImagingFactory; source: IE_IWICBitmapSource; dest: TIEBitmap; nativePixelFormat: boolean = true; OnProgressFunc: TIEProgressEvent = nil);
...
  CheckHResult( converter.Initialize( source, pixelFormatGUID, IE_WICBitmapDitherTypeNone, nil, 0.0, 0 ));
...  

// Force use of IELib DLL for improved performance
// ImageEn will attempt to load the DLL even if it's not in the EXE folder. If the DLL isn't found or is an old version, an error will be raised
IEGlobalSettings().JPEGEngine := ieenDLL;
IEGlobalSettings().PNGEngine := ieenDLL;
IEGlobalSettings().JPEG2000Engine := ieenDLL;
IEGlobalSettings().CameraRawEngine := ieenDLL;