An entity from an application we have no reader for — e.g. an Autodesk Raster
Design embedded raster image — now arrives as `Unknown` (acadrust 769741d) and
rendered as nothing at all, so the drawing silently lost it with no hint that
anything was there.
Such entities almost always ship proxy graphics: the vector preview their author
cached for precisely this case, and what AutoCAD itself falls back to when the
object enabler is absent. Decode it and draw it, so the entity holds its real
place and size.
The record grammar has no reference implementation to copy — LibreDWG keeps the
blob raw ("see par 29") and ACadSharp stores the bytes without parsing them — so
rather than infer a general decoder from one sample, `proxy_graphics` accepts a
single polyline record and only when the blob matches it byte-for-byte: sizes
must agree, the points must consume every remaining byte, and coordinates must
be finite. Anything else returns None and draws nothing, exactly as before, so
a file this does not model cannot regress or sprout invented geometry.
Verified on a Raster Design drawing: its 140-byte preview decodes with 0 bytes
left over to the image frame (1192.149 x 877.824, closed), matching what ODA
reports for the same entity. Unit-tested against that real blob.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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