dschmidt opened a new pull request, #3095:
URL: https://github.com/apache/tika/pull/3095
Office documents carry their preview image as a vector metafile: the OOXML
`docProps/thumbnail.emf` of Word (an EMF wrapping a WMF) and `thumbnail.wmf` of
Excel, and the SummaryInformation thumbnail (PIDSI_THUMBNAIL,
`CF_METAFILEPICT`, a WMF) of the OLE2 formats. Neither is usable as a preview
outside Windows, and outside the JVM there is no maintained EMF/WMF rasterizer,
while POI's HEMF/HWMF can draw both.
Following the PDF parser's rendering design:
- `POIMetafileRenderer` (`poi-metafile-renderer`) is a `Renderer` for
`image/emf` and `image/wmf`: the POI picture drawn onto a white canvas, a PNG
of a configurable width. The WMF thumbnails Word writes consist of a
`setWindowExt` and a `dibStretchBlt` record only, for which POI cannot compute
bounds; those are rendered from the record's bitmap.
- `EMFParser` and `WMFParser` implement `RenderingParser` and, with
`"emf-parser"` / `"wmf-parser": {"renderImage": true, "renderWidth": 800}` (off
by default), emit the rendering as a `RENDERING` embedded document named after
the image. An injected renderer is used when it supports the type, the POI one
otherwise. The shared config and emission live in `MetafileParserConfig` and
`MetafileRendering`.
- `OfficeParser` emits the SummaryInformation thumbnail as a `THUMBNAIL`
embedded document (`image/wmf`, `thumbnail.wmf`), consistent with the docProps
thumbnail of the OOXML parsers. Two PowerPoint tests count one embedded
document more because of it.
Verified against tika-server with `/unpack`: docx, xlsx, doc, xls and ppt
files that carry a thumbnail yield it at depth 1 and its PNG rendering at depth
2.
https://issues.apache.org/jira/browse/TIKA-4855
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