Add thumbnail to all 3MF files, and add relation and content-type metadata

plugins/3MFWriter/ThreeMFWorkspaceWriter.py

@@ -5,8 +5,6 @@ import configparser
 from io import StringIO
 import zipfile
 
-from PyQt5.QtCore import QBuffer
-
 from UM.Application import Application
 from UM.Logger import Logger
 from UM.Preferences import Preferences
@@ -16,7 +14,7 @@ from UM.i18n import i18nCatalog
 catalog = i18nCatalog("cura")
 
 from cura.Utils.Threading import call_on_qt_thread
-from cura.Snapshot import Snapshot
+
 
 class ThreeMFWorkspaceWriter(WorkspaceWriter):
     def __init__(self):
@@ -88,23 +86,7 @@ class ThreeMFWorkspaceWriter(WorkspaceWriter):
 
             self._writePluginMetadataToArchive(archive)
 
-            # Attempt to add a thumbnail
+            # Close the archive & reset states.
-            Logger.log("d", "Creating thumbnail image...")
-            try:
-                snapshot = Snapshot.snapshot(width = 300, height = 300)
-            except Exception:
-                snapshot = None
-                Logger.logException("w", "Failed to create snapshot image")
-
-            if snapshot:
-                thumbnail_file = zipfile.ZipInfo("Metadata/thumbnail.png")
-
-                thumbnail_buffer = QBuffer()
-                thumbnail_buffer.open(QBuffer.ReadWrite)
-                snapshot.save(thumbnail_buffer, "PNG")
-                archive.writestr(thumbnail_file, thumbnail_buffer.data())
-
-            # Close the archive & reset states
             archive.close()
         except PermissionError:
             self.setInformation(catalog.i18nc("@error:zip", "No permission to write the workspace here."))

plugins/3MFWriter/ThreeMFWriter.py

@@ -10,6 +10,10 @@ from UM.Application import Application
 from UM.Scene.SceneNode import SceneNode
 
 from cura.CuraApplication import CuraApplication
+from cura.Utils.Threading import call_on_qt_thread
+from cura.Snapshot import Snapshot
+
+from PyQt5.QtCore import QBuffer
 
 import Savitar
 
@@ -149,6 +153,22 @@ class ThreeMFWriter(MeshWriter):
             relations_element = ET.Element("Relationships", xmlns = self._namespaces["relationships"])
             model_relation_element = ET.SubElement(relations_element, "Relationship", Target = "/3D/3dmodel.model", Id = "rel0", Type = "http://schemas.microsoft.com/3dmanufacturing/2013/01/3dmodel")
 
+            # Attempt to add a thumbnail
+            snapshot = self._createSnapshot()
+            if snapshot:
+                thumbnail_buffer = QBuffer()
+                thumbnail_buffer.open(QBuffer.ReadWrite)
+                snapshot.save(thumbnail_buffer, "PNG")
+
+                thumbnail_file = zipfile.ZipInfo("Metadata/thumbnail.png")
+                # Don't try to compress snapshot file, because the PNG is pretty much as compact as it will get
+                archive.writestr(thumbnail_file, thumbnail_buffer.data())
+
+                # Add PNG to content types file
+                thumbnail_type = ET.SubElement(content_types, "Default", Extension = "png", ContentType = "image/png")
+                # Add thumbnail relation to _rels/.rels file
+                thumbnail_relation_element = ET.SubElement(relations_element, "Relationship", Target = "/Metadata/thumbnail.png", Id = "rel1", Type = "http://schemas.openxmlformats.org/package/2006/relationships/metadata/thumbnail")
+
             savitar_scene = Savitar.Scene()
 
             metadata_to_store = CuraApplication.getInstance().getController().getScene().getMetaData()
@@ -212,3 +232,17 @@ class ThreeMFWriter(MeshWriter):
                 self._archive = archive
 
         return True
+
+    @call_on_qt_thread  # must be called from the main thread because of OpenGL
+    def _createSnapshot(self) -> None:
+        Logger.log("d", "Creating thumbnail image...")
+        if not CuraApplication.getInstance().isVisible:
+            Logger.log("w", "Can't create snapshot when renderer not initialized.")
+            return None
+        try:
+            snapshot = Snapshot.snapshot(width = 300, height = 300)
+        except:
+            Logger.logException("w", "Failed to create snapshot image")
+            return None
+
+        return snapshot