--- a/NEWS	Mon Jan 06 17:07:27 2025 +0100
+++ b/NEWS	Mon Jan 06 17:10:09 2025 +0100
@@ -8,6 +8,8 @@
   operating system native CA store (if any).  This is equivalent to the --ca-native
   curl option.
 * Housekeeper plugin: fixed the "Force" configuration that was ineffective.
+* Housekeeper plugin: allow transcoding to lossy transfer syntax.  Orthanc will keep
+  the SOPInstanceUID untouched in this case.
 
 
 Version 1.12.5 (2024-12-17)

--- a/OrthancServer/Sources/ServerContext.cpp	Mon Jan 06 17:07:27 2025 +0100
+++ b/OrthancServer/Sources/ServerContext.cpp	Mon Jan 06 17:10:09 2025 +0100
@@ -938,10 +938,20 @@
         source.SetExternalBuffer(dicom->GetBufferData(), dicom->GetBufferSize());
         
         IDicomTranscoder::DicomImage transcoded;
+        
         if (Transcode(transcoded, source, syntaxes, true /* allow new SOP instance UID */))
         {
           std::unique_ptr<ParsedDicomFile> tmp(transcoded.ReleaseAsParsedDicomFile());
 
+          if (isReconstruct)
+          {
+            // when reconstructing, we always want to keep the DICOM IDs untouched even if the transcoding has generated a new SOPInstanceUID.
+            const Orthanc::ParsedDicomFile& sourceDicom = dicom->GetParsedDicomFile();
+            std::string sopInstanceUid;
+            sourceDicom.GetTagValue(sopInstanceUid, DICOM_TAG_SOP_INSTANCE_UID);
+            tmp->ReplacePlainString(DICOM_TAG_SOP_INSTANCE_UID, sopInstanceUid);
+          }
+
           std::unique_ptr<DicomInstanceToStore> toStore(DicomInstanceToStore::CreateFromParsedDicomFile(*tmp));
           toStore->SetOrigin(dicom->GetOrigin());
           toStore->CopyMetadata(dicom->GetMetadata());