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      "source": [
        "%gui qt"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n# Apply Contour Filter on an Image\n\nSimple use of SceneCanvas to display an Image.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
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      "source": [
        "import sys\n\nfrom vispy import scene, app\nfrom vispy.visuals.filters import IsolineFilter\nfrom vispy.io import load_data_file, read_png\n\ncanvas = scene.SceneCanvas(keys='interactive')\ncanvas.size = 600, 800\ncanvas.show()\n\n# Set up a viewbox to display the image with interactive pan/zoom\nview = canvas.central_widget.add_view()\n\ninterpolation = 'cubic'\nimg_data = read_png(load_data_file('mona_lisa/mona_lisa_sm.png'))\nimage = scene.visuals.Image(img_data, interpolation=interpolation,\n                            parent=view.scene, method='impostor')\nlevel = 10\niso = IsolineFilter(level=level, width=1., color='white')\n\n# Set 2D camera (the camera will scale to the contents in the scene)\nview.camera = scene.PanZoomCamera(aspect=1)\n# flip y-axis to have correct aligment\nview.camera.flip = (0, 1, 0)\n# select face part\nview.camera.rect = (160, 130, 240, 200)\n\ncanvas.title = ('Spatial Filtering using %s Filter - Isoline %d level'\n                % (image.interpolation, iso.level))\n\n# get interpolation functions from Image\nnames = image.interpolation_functions\nact = names.index(interpolation)\n\n\n# Implement key presses\n@canvas.events.key_press.connect\ndef on_key_press(event):\n    global act, level, first, interpolation\n    if event.key in ['Left', 'Right']:\n        if event.key == 'Right':\n            step = 1\n        else:\n            step = -1\n        act = (act + step) % len(names)\n        image.interpolation = names[act]\n\n    if event.key in ['Up', 'Down']:\n        iso.level += 1 if event.key == 'Up' else -1\n    canvas.title = ('Spatial Filtering using %s Filter - Isoline %d level'\n                    % (image.interpolation, iso.level))\n    canvas.update()\n\n\n# attaching of isoline filter via timer\ndef on_timer1(event):\n    image.attach(iso)\n    canvas.update()\n\ntimer1 = app.Timer('auto', iterations=1, connect=on_timer1, start=True)\n\nif __name__ == '__main__' and sys.flags.interactive == 0:\n    app.run()"
      ]
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