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https://issues.apache.org/jira/browse/TIKA-4856?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18115833#comment-18115833
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ASF GitHub Bot commented on TIKA-4856:
--------------------------------------

Copilot commented on code in PR #3179:
URL: https://github.com/apache/tika/pull/3179#discussion_r4022176529


##########
tika-pipes/tika-pipes-core/src/main/resources/org/apache/tika/pipes/core/presets/render-thumbnails.json:
##########
@@ -0,0 +1,11 @@
+{
+  // the same first-page and EMF/WMF renders as "thumbnails", added to a full 
parse:
+  // text, OCR, embedded documents and everything else stay as the server 
configures them
+  "pdf-parser": {
+    "imageStrategy": "RENDER_PAGES_BEFORE_PARSE",
+    "maxRenderedPages": 1,
+    "rendering": {"dpi": 96, "imageType": "RGB"}
+  },

Review Comment:
   Applying a preset uses `ParseContext.copyFrom()`, which replaces an existing 
JSON entry when the key matches. A server that has a `parse-context` 
`pdf-parser` override therefore loses its text/OCR/page settings when this 
preset is selected, contradicting the claim that the full parse keeps the 
server configuration (the same issue applies to the EMF/WMF entries below). 
Merge the component configuration with the server context or explicitly 
avoid/clarify this same-key replacement before shipping.



##########
CHANGES.txt:
##########
@@ -1,5 +1,7 @@
 Release 4.1.0 - unreleased
 
+   * New catalog presets, inert until the config names them.(TIKA-4856).

Review Comment:
   Add a space before the issue reference; the new release-note sentence 
currently reads `names them.(TIKA-4856)`.





> /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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