Add image cache folder feature

[Intelligent2013]

Source ticket: metanorma/metanorma-ogc#600

To do: in case of big XML (>50mb) extract images from the XML to the temporarily folder, so the XML will contains the file links only.

[ronaldtse]

Is this an mn2pdf thing or a general Metanorma XML feature?

[Intelligent2013]

Is this an mn2pdf thing or a general Metanorma XML feature?

@ronaldtse mn2pdf thing.

But I've found the Metanorma document attribute :data-uri-image: false (https://www.metanorma.org/author/ref/document-attributes/#visual-appearance) that allows to don't integrate the images inline in the XML. I this case the Presentation XML contains the images paths instead of base64 encoded images, like this:

<image src="images/figure-overview.png" ...

:data-uri-image: false should solve the initial issue [mn2pdf] Exception in thread "main" java.lang.OutOfMemoryError: Java heap space.

:data-uri-image: affects on HTML output also:

Encode all images in HTML output as inline data-URIs.

@ronaldtse now I don't sure that I have to do it:

To do: in case of big XML (>50mb) extract images from the XML to the temporarily folder, so the XML will contains the file links only.

What do you think? :data-uri-image: false is enough to solve the issue, or should I 'extract images from XML into the temp folder` in any case?

[Intelligent2013]

mn2pdf updated. Now mn2pdf extracts the images from base64 to the temporarily folder on disk. I.e. base64 streams don't spent the memory in XSLT processing.