Tools: add script to create snapshots in headless mode

src/Tools/make_snapshot.py

@@ -0,0 +1,78 @@
+# (c) 2022 Werner Mayer LGPL
+
+"""
+The module can be used from another module with:
+
+from make_snapshot import make_snapshot
+make_snapshot("file.stl", "image.png")
+
+This other module then can be used with:
+
+FreeCAD -c make_snapshot_from_file.py
+
+or
+
+FreeCADCmd make_snapshot_from_file.py
+"""
+
+import FreeCAD
+import FreeCADGui
+import os
+import importlib
+import sys
+from PySide2 import QtGui
+
+def init_gui():
+    try:
+        FreeCADGui.setupWithoutGUI()
+    except Exception as e:
+        pass
+
+def make_snapshot(input_file, output_file, size = 48):
+    from pivy import coin
+
+    ext = os.path.splitext(input_file)[1][1:]
+    mod = FreeCAD.getImportType(ext)
+    if len(mod) == 0:
+        print ("Cannot load file {}".format(input_file))
+        return
+
+    # use the first listed module
+    module = importlib.import_module(mod[0])
+    module.open(input_file)
+
+    doc = FreeCAD.ActiveDocument
+    if doc is None:
+        print ("No active document")
+        return
+
+    init_gui()
+    nodes = [FreeCADGui.subgraphFromObject(obj) for obj in doc.Objects]
+
+    # add light and camera so that the rendered geometry is visible
+    root = coin.SoSeparator()
+    light = coin.SoDirectionalLight()
+    cam = coin.SoOrthographicCamera()
+    root.addChild(cam)
+    root.addChild(light)
+    for node in nodes:
+        root.addChild(node)
+
+    # do the rendering now
+    axo = coin.SbRotation(-0.353553, -0.146447, -0.353553, -0.853553)
+    width = size
+    height = size
+    viewport = coin.SbViewportRegion(width, height)
+    cam.orientation.setValue(axo)
+    cam.viewAll(root,viewport)
+    off = FreeCADGui.SoQtOffscreenRenderer(width, height)
+    off.setBackgroundColor(1,1,1)
+    root.ref()
+
+    # A QGuiApplication is needed to create an OpenGL context
+    if QtGui.QGuiApplication.instance() is None:
+        app = QtGui.QGuiApplication(sys.argv)
+
+    off.render(root)
+    off.writeToImage(output_file)
+    root.unref()