Add a thumbnail to 3mf projects

plugins/3MFWriter/ThreeMFWorkspaceWriter.py

@@ -5,6 +5,8 @@ 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
@@ -14,7 +16,7 @@ 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):
@@ -86,7 +88,23 @@ class ThreeMFWorkspaceWriter(WorkspaceWriter):
 
             self._writePluginMetadataToArchive(archive)
 
-            # Close the archive & reset states.
+            # Attempt to add a thumbnail
+            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."))