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https://issues.apache.org/jira/browse/TIKA-4856?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18113085#comment-18113085
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ASF GitHub Bot commented on TIKA-4856:
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dschmidt commented on PR #3148:
URL: https://github.com/apache/tika/pull/3148#issuecomment-5594050162
No worries, the whole topic is a bit confusing and tough to crack. Thanks
for your effort in solving my request in a sustainable matter. Happy to help
with that wherever I can.
Right now I'm completely overtired and can't think straight tho 😴
So I'm afraid I can't fully answer your questions right now, but yeah, I can
define my requirement or my initial issue further:
I found it harder than it should be to figure out the right request options
to get all possible thumbnails. Also it looked like it would be subject to
subtle changes from tika version to tika version.
What I need in the end is a response for which I can implement a simple rule
to get the thumbnail - in the two scenarios described above.
Something like first thumbnail or thumbnail which is a rendering is easy
enough to implement.
If we can reduce the size of the response, that would be nice but not a
requirement for me.
To make it more concrete: I want to implement thumbnails in OpenCloud
without having to adjust the rules specifically for every tika version and I
don't want to know which formats tika provides thumbnails for at all.
That's why I need/want a generic form which is stable
> /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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