{
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    {
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      "source": [
        "%gui qt"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n# Show a textured quad\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
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      "source": [
        "import numpy as np\n\nfrom vispy import gloo, app\nfrom vispy.gloo import Program\n\nvertex = \"\"\"\n    attribute vec2 position;\n    attribute vec2 texcoord;\n    varying vec2 v_texcoord;\n    void main()\n    {\n        gl_Position = vec4(position, 0.0, 1.0);\n        v_texcoord = texcoord;\n    } \"\"\"\n\nfragment = \"\"\"\n    uniform sampler2D texture;\n    varying vec2 v_texcoord;\n    void main()\n    {\n        gl_FragColor = texture2D(texture, v_texcoord);\n    } \"\"\"\n\n\ndef checkerboard(grid_num=8, grid_size=32):\n    row_even = grid_num // 2 * [0, 1]\n    row_odd = grid_num // 2 * [1, 0]\n    Z = np.row_stack(grid_num // 2 * (row_even, row_odd)).astype(np.uint8)\n    return 255 * Z.repeat(grid_size, axis=0).repeat(grid_size, axis=1)\n\n\nclass Canvas(app.Canvas):\n    def __init__(self):\n        app.Canvas.__init__(self, size=(512, 512), title='Textured quad',\n                            keys='interactive')\n\n        # Build program & data\n        self.program = Program(vertex, fragment, count=4)\n        self.program['position'] = [(-1, -1), (-1, +1),\n                                    (+1, -1), (+1, +1)]\n        self.program['texcoord'] = [(0, 0), (1, 0), (0, 1), (1, 1)]\n        self.program['texture'] = checkerboard()\n\n        gloo.set_viewport(0, 0, *self.physical_size)\n\n        self.show()\n\n    def on_draw(self, event):\n        gloo.set_clear_color('white')\n        gloo.clear(color=True)\n        self.program.draw('triangle_strip')\n\n    def on_resize(self, event):\n        gloo.set_viewport(0, 0, *event.physical_size)\n\nif __name__ == '__main__':\n    c = Canvas()\n    app.run()"
      ]
    }
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