tested with my image in example package.
http://www.simco-ion.nl/typo3conf/ext/uwkm_offer/Lib/examples/LayoutAndGeneral/addHeader/example_addHeader_2.docx
works just fine.
Strange enough if i make any tests everything works fine.. but not sure why when i execute this functions from my extension well we get unexpected results.
although using namespaced version in extension so it shouldn't really conflict with any other component which is used in cms.