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https://issues.apache.org/jira/browse/TIKA-4856?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18110782#comment-18110782
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ASF GitHub Bot commented on TIKA-4856:
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dschmidt commented on PR #3096:
URL: https://github.com/apache/tika/pull/3096#issuecomment-5513786424
Just to make sure I get it right:
🤖 suggests to just document what parse-context to use for the specific
rendering thumbnail extraction behavior?
It's exactly what I wanted to avoid to be honest - it doesn't make sense as
global config (in the metadata request I want OCR, in the thumbnails request I
don't), I don't want to hardcode this in my application and I don't want to
make it config in my application.
The idea is to make it *easy* to retrieve thumbnails (as part of a metadata
request and also as a standalone "just give me a thumbnail, I don't care").
In my use case (OpenCloud) I want to support previews for as many file
formats as possible and Tika itself will always know better what it supports
than any third party consumer. Moreover, I would really like to avoid having to
maintain configs for different Tika versions,
Maybe we can have some kind of preset functionality?
Tika could provide some default presets like `render-thumbnails` but users
could also provide custom ones via settings ... I'm completely open to any idea
or suggestion, I just really want to keep this config out of consuming
applications
P.S.: yes, of course we can split maxRenderedPages out of this PR.
> /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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