Dominik Schmidt created TIKA-4831:
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Summary: Add content-based detection and a parser for GeoGebra
files (ggb, ggs, ggt)
Key: TIKA-4831
URL: https://issues.apache.org/jira/browse/TIKA-4831
Project: Tika
Issue Type: New Feature
Reporter: Dominik Schmidt
GeoGebra files are currently only recognized by file extension. The mime
registry has glob-only entries for {{application/vnd.geogebra.file}} ({{*.ggb}})
and {{application/vnd.geogebra.tool}} ({{*.ggt}}), but both formats are zip
containers and the entries are not declared as sub-classes of
{{application/zip}}. As a result, as soon as content is available, magic
detection returns {{application/zip}} and the filename hint is discarded in
{{MimeTypes.applyHint()}} - even when the resource name is known. Content-only
detection (no filename) has no way to identify the formats at all, and the
newer GeoGebra formats {{*.ggs}} (Notes/Slides) and {{*.ggp}} (Pinboard) are
missing from the registry entirely.
There is also no parser for any of the GeoGebra formats: files fall through to
the generic {{PackageParser}}, which extracts the zip entries but produces no
document metadata and no usable text (the {{geogebra.xml}} construction is
emitted as raw XML through the XML parser).
Proposed improvement:
* mime registry: declare {{application/vnd.geogebra.file}} and
{{application/vnd.geogebra.tool}} as {{sub-class-of application/zip}}; add
{{application/vnd.geogebra.slides}} ({{*.ggs}}, zip-based) and
{{application/vnd.geogebra.pinboard}} ({{*.ggp}}, JSON-based)
* a {{ZipContainerDetector}} that identifies the formats without a filename by
their well-known entries: {{geogebra.xml}} (worksheet), {{structure.json}}
plus {{_slideN/geogebra.xml}} (Notes/Slides), {{geogebra_macro.xml}} (tool);
a worksheet with macros contains both {{geogebra.xml}} and
{{geogebra_macro.xml}}, so the decision must be made after all entry names
have been seen
* a {{GeoGebraParser}} for ggb/ggs/ggt that extracts the construction metadata
(title, author, date) and application name/version, emits the user-visible
text (text objects, rich-text notes, captions, macro names/help) as XHTML,
and emits the embedded {{geogebra_thumbnail.png}} (root, or the first slide's
for Notes/Slides) as an embedded document marked
{{embeddedResourceType=THUMBNAIL}}, following the existing convention in the
OOXML, ODF and iWork parsers, so downstream consumers of {{/unpack/all}}
sidecars can identify the preview image
Use case: file sync/share servers (e.g. OpenCloud) use Tika for content
extraction and for serving embedded preview images; with the THUMBNAIL marker
they can select the representative preview of a GeoGebra file the same way as
for Office documents.
Pull request to follow.
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