Re: What is the format of the filename of images in the Pictures/ folder inside odt?

[Adam Ryczkowski <adam.ryczkowski-fT3I5MopIUtcgLbgGiZUJQ@public.gmane.org>]

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When Pandoc creates ODT file from HTML containing SVG images, it losslessly 
embeds the images as-is. That's a problem for me, because my pipeline does 
some automatic transformations to the document using LibreOffice UNO API 
and ultimately saves as DOCX. When LibreOffice saves a ODT file containing 
the SVG images into DOCX, it rasterizes the images in a very poor 
resolution, that is according to folks in the LibreOffice forum, 
uncontrollable. But there is a trick: I can use Inkscape to do convert the 
SVG images into EMF. EMF files are not rasterized by LibreOffice when it 
saves the document as DOCX. 

The problem is that the EMF files have obviously different binary content 
than SVG originals. When I replace them in the "Pictures/" folder inside 
the ODT, LibreOffice notices that the file name of the EMF pictures does 
not match their hash and claims the "image is corrupted" and gives an 
option to repair. Unfortunately, that repair dialog cannot get automated in 
the headless environment, which means I need to know how to make the 
"non-broken" ODT document in the first place. For that I need to know the 
hashing scheme. 

I tried to read the Pandoc sources to get the answer myself, but my zero 
knowledge of Haskell is a major obstacle. 

My gut feeling says the answer is somewhere in the 
`pandoc/src/Text/Pandoc/Writers/OpenDocument.hs`. 

On Saturday, December 2, 2023 at 9:05:42 PM UTC John MacFarlane wrote:

> Why is it necessary to do this? Docx can handle svgs, can't it?
>
> > On Dec 2, 2023, at 6:16 AM, Adam Ryczkowski <adam.ry...-fT3I5MopIUtcgLbgGiZUJQ@public.gmane.org> 
> wrote:
> > 
> > Hi!
> > 
> > I write a script that replaces "svg" images with "emf" in the odt in 
> order to allow lossless convertion to "docx" format using LibreOffice. 
> > 
> > The problem is that mere replacing the files and fixing the 
> `content.xml` does not suffice. The image file name is some form of hash of 
> its contents. If the contents does not match, Libreoffice reports the 
> document to be "broken" (but allows to repair). Alas, this repair cannot be 
> automated. 
> > 
> > I tried to get that from the Pandoc source code, but Haskell's syntax 
> seem too alien to me. 
> > 
> > What is the naming convention for the files in the Pictures/ folder?
> > 
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>

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