When a document is saved, that contains a math formula object, not only the object with MathML is written but in addition an image in format "VCLMTF". That should not happen, because such image is useless. No other application can read that format and LibreOffice, Apache OpenOffice or MS Office do not need it, because they can read the original MathML. The purpose of a second object in a <draw:frame> element is, that applications, which are not able to read the first object (here the MathML) can show the second object instead. For this purpose the format "VCLMTF" is totally unsuitable. For that purpose a png-format would be best.
OK, but isn't VCLMTF (aka SVM2) a vector meta, not a bitmap representation? Rather than holding object replacement as PNG, why not SVG or EMF+? But I'm unclear about where the ObjectReplacements directory contents of an ODF archive would even be used. If it is not needed for LO, AOO or MS Office does it need to be populated? It an Obeject Replacement required for sm/MathML formulas?
(In reply to V Stuart Foote from comment #1) > OK, but isn't VCLMTF (aka SVM2) a vector meta, not a bitmap representation? > Rather than holding object replacement as PNG, why not SVG or EMF+? Rendering of SVG or EMF+ is not so common. Especially if an application is not able to render MathML, then it is likely, that it cannot render SVG or EMF+ too. WMF might work. Our ancient HTML export uses gif. But I thing, png is most common. > > But I'm unclear about where the ObjectReplacements directory contents of an > ODF archive would even be used. If it is not needed for LO, AOO or MS Office > does it need to be populated? For example Softmaker uses the replacement object. I have tested gif and png. Those work for Softmaker. I have not tested wmf. > It an Obeject Replacement required for sm/MathML formulas? LibreOffice, AOO or MsOffice need no Object Replacement. Flat ODF has an Object Replacement in base64 encoding. I have not tested, which format it is. There it is not needed at all, because only LibreOffice read/writes flat ODF and for using flat ODF in github or similar this base64 encoded part is rather hindering. So for flat ODF it should be dropped. Our export to XHTML has no Object Replacement.
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