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    {
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      "source": [
        "%gui qt"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n# Show an Image\n\nDraw a new array of random image pixels on every draw cycle.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
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      "source": [
        "import numpy as np\n\nfrom vispy.util.transforms import ortho\nfrom vispy import gloo\nfrom vispy import app\n\n\n# Image to be displayed\nW, H = 64, 48\nimg_array = np.random.uniform(0, 1, (W, H)).astype(np.float32)\n\n# A simple texture quad\ndata = np.zeros(4, dtype=[('a_position', np.float32, 2),\n                          ('a_texcoord', np.float32, 2)])\ndata['a_position'] = np.array([[0, 0], [W, 0], [0, H], [W, H]])\ndata['a_texcoord'] = np.array([[0, 0], [0, 1], [1, 0], [1, 1]])\n\n\nVERT_SHADER = \"\"\"\n// Uniforms\nuniform mat4 u_model;\nuniform mat4 u_view;\nuniform mat4 u_projection;\nuniform float u_antialias;\n\n// Attributes\nattribute vec2 a_position;\nattribute vec2 a_texcoord;\n\n// Varyings\nvarying vec2 v_texcoord;\n\n// Main\nvoid main (void)\n{\n    v_texcoord = a_texcoord;\n    gl_Position = u_projection * u_view * u_model * vec4(a_position,0.0,1.0);\n}\n\"\"\"\n\nFRAG_SHADER = \"\"\"\nuniform sampler2D u_texture;\nvarying vec2 v_texcoord;\nvoid main()\n{\n    gl_FragColor = texture2D(u_texture, v_texcoord);\n    gl_FragColor.a = 1.0;\n}\n\n\"\"\"\n\n\nclass Canvas(app.Canvas):\n\n    def __init__(self):\n        app.Canvas.__init__(self, keys='interactive', size=((W * 5), (H * 5)))\n\n        self.program = gloo.Program(VERT_SHADER, FRAG_SHADER)\n        self.texture = gloo.Texture2D(img_array, interpolation='linear')\n\n        self.program['u_texture'] = self.texture\n        self.program.bind(gloo.VertexBuffer(data))\n\n        self.view = np.eye(4, dtype=np.float32)\n        self.model = np.eye(4, dtype=np.float32)\n        self.projection = np.eye(4, dtype=np.float32)\n\n        self.program['u_model'] = self.model\n        self.program['u_view'] = self.view\n        self.projection = ortho(0, W, 0, H, -1, 1)\n        self.program['u_projection'] = self.projection\n\n        gloo.set_clear_color('white')\n\n        self._timer = app.Timer('auto', connect=self.update, start=True)\n\n        self.show()\n\n    def on_resize(self, event):\n        width, height = event.physical_size\n        gloo.set_viewport(0, 0, width, height)\n        self.projection = ortho(0, width, 0, height, -100, 100)\n        self.program['u_projection'] = self.projection\n\n        # Compute thje new size of the quad\n        r = width / float(height)\n        R = W / float(H)\n        if r < R:\n            w, h = width, width / R\n            x, y = 0, int((height - h) / 2)\n        else:\n            w, h = height * R, height\n            x, y = int((width - w) / 2), 0\n        data['a_position'] = np.array(\n            [[x, y], [x + w, y], [x, y + h], [x + w, y + h]])\n        self.program.bind(gloo.VertexBuffer(data))\n\n    def on_draw(self, event):\n        gloo.clear(color=True, depth=True)\n        img_array[...] = np.random.uniform(0, 1, (W, H)).astype(np.float32)\n        self.texture.set_data(img_array)\n        self.program.draw('triangle_strip')\n\n\nif __name__ == '__main__':\n    canvas = Canvas()\n    app.run()"
      ]
    }
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