FreeCAD

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