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https://issues.apache.org/jira/browse/TIKA-4856?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18110784#comment-18110784
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ASF GitHub Bot commented on TIKA-4856:
--------------------------------------
tballison commented on PR #3096:
URL: https://github.com/apache/tika/pull/3096#issuecomment-5513793761
This would leave client side to arbitrate thumbnail vs rendering. This is an
option to leave just one per:
```
Yes — there's a properly Tika-shaped home for it: ship the priority logic as
an UnpackSelector implementation, registered as a @TikaComponent. That's
exactly what the pluggable
selector interface exists for, and the PR's own docs already point people
there ("Custom EmbeddedDocumentExtractor is ignored; use UnpackSelector"). The
contributor keeps his
selection logic server-side, it's addressed purely by config name — and it
gets something his endpoint never had: it works everywhere pipes UNPACK mode
works, including
tika-async-cli batch runs, not just one tika-server route.
Concretely: a ThumbnailUnpackSelector next to StandardUnpackSelector in
tika-pipes-core, encoding his priority (raster THUMBNAIL at depth 1 → RENDERING
below a vector THUMBNAIL →
first-page RENDERING), selecting at most one document. Parse time:
{
"parse-context": {
"pdf-parser": { "imageStrategy": "RENDER_PAGES_AT_PAGE_END",
"maxRenderedPages": 1,
"ocr": { "dpi": 96, "imageType": "RGB" } },
"emf-parser": { "renderImage": true,
"renderOnlyEmbeddedResourceTypes": ["THUMBNAIL"] },
"wmf-parser": { "renderImage": true,
"renderOnlyEmbeddedResourceTypes": ["THUMBNAIL"] },
"thumbnail-unpack-selector": {},
"unpack-config": { "outputFormat": "FRICTIONLESS", "outputMode":
"ZIPPED",
"includeFullMetadata": true },
"embedded-limits": { "maxDepth": 3, "maxCount": 20 }
}
}
Result: a package containing exactly one image plus its metadata —
functionally his {metadata, image} response, minus the bespoke route. Or baked
into tika-config.json's
parse-context for a dedicated thumbnail server with zero request config.
```
> /unpack/thumbnail: return the document thumbnail with its metadata
> ------------------------------------------------------------------
>
> Key: TIKA-4856
> URL: https://issues.apache.org/jira/browse/TIKA-4856
> Project: Tika
> Issue Type: New Feature
> Reporter: Dominik Schmidt
> Priority: Major
>
> With TIKA-4850 through TIKA-4855 every container format that carries a
> thumbnail emits it as a THUMBNAIL embedded document, the PDF parser renders
> pages as RENDERING documents, and the EMF/WMF renderer turns the vector
> thumbnails of Office documents into raster ones. Getting "the thumbnail of
> this file" out of that still takes format knowledge on the client: the
> THUMBNAIL of a Word or Excel file is an EMF/WMF whose usable form is the
> RENDERING underneath it, a PDF has no THUMBNAIL but a page RENDERING, the
> THUMBNAIL of a DOCX inside a ZIP is not the ZIP's, and with rendering enabled
> the picture of an embedded OLE object is a RENDERING too. Plus the request
> config that switches the renderers on.
> Proposal: POST /unpack/thumbnail next to /unpack and /unpack/all, multipart
> like them. It runs the usual forked parse in unpack mode with a fixed parse
> context (PDF page 1 rendered, EMF/WMF rendered) and picks, in this order: the
> raster THUMBNAIL at depth 1; the rendering of that thumbnail; the depth-1
> RENDERING of PDF page 1. The endpoint extracts what the document carries; it
> does not resize, convert or generate previews.
> The response is JSON: the /rmeta metadata object of the selected embedded
> document, and the image as base64. Thumbnails are small, so the encoding
> overhead does not matter, and the caller gets type, dimensions, origin
> (stored thumbnail or rendering, tk:rendering:rendered-by) and path in one
> round trip without unpacking a zip. 204 when the document has no thumbnail.
> {
> "metadata": {
> "Content-Type": "image/png",
> "Content-Length": "8459",
> "tiff:ImageWidth": "800",
> "tiff:ImageLength": "1131",
> "tk:embedded-resource-type": "RENDERING",
> "tk:embedded-resource-path": "/thumbnail.emf/thumbnail.png",
> "tk:embedded-depth": "2",
> "tk:rendering:rendered-by": "poi-metafile-renderer",
> "tk:resource-name": "thumbnail.png"
> },
> "image": "iVBORw0KGgoAAAANSUhEUgAA..."
> }
> To keep the selection rule short, the metafile renderer could give the
> rendering of a THUMBNAIL the THUMBNAIL type as well (its
> tk:rendering:rendered-by tells it apart), so a raster thumbnail is a
> THUMBNAIL regardless of whether the document stored it as PNG or as EMF.
> What do you think?
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