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https://issues.apache.org/jira/browse/TIKA-4856?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18110788#comment-18110788
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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-5513854932
Like this?
```
{
"presets": {
"render-thumbnails": {
"pdf-parser": { "imageStrategy": "RENDER_PAGES_AT_PAGE_END",
"maxRenderedPages": 1,
"ocr": { "dpi": 150, "imageType": "RGB" } }
},
"our-archival-ocr": {
"pdf-parser": { "ocr": { "strategy": "OCR_AND_TEXT_EXTRACTION",
"dpi": 300 } }
}
}
}
(First block overrides a built-in by name — admin wins over Tika; second
is a purely custom one.)
Parse time — the reference lives in the config part, next to (and under)
the request's own parse-context:
{ "presets": ["render-thumbnails"] }
on POST /rmeta/text/config for his index request — metadata, text, and
thumbnail in one parse. And the standalone "just give me a thumbnail, I don't
care" case is POST /unpack
with:
{ "presets": ["thumbnail"] }
where thumbnail is a second built-in preset that bundles render-thumbnails
plus the selection: thumbnail-unpack-selector (his ThumbnailSelector logic as
an UnpackSelector
component), unpack-config with Frictionless output, and embedded-limits.
One image plus its metadata comes back; no /unpack/thumbnail route needed. A
request can still layer its
own overrides: {"presets": ["render-thumbnails"], "parse-context":
{"pdf-parser": {...}}} — request wins, per component, which is exactly the
layering semantics
ThumbnailDefaults.applyTo already implements.
```
> /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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