#!/usr/bin/env python
# encoding: utf-8

# kivy_memory_image.py
# How to load an image from memory in Kivy
# http://mornie.org/blog/2013/11/06/how-load-image-memory-kivy/

# Copyright (c) 2013, Daniele Tricoli <eriol@mornie.org>
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
# 3. All advertising materials mentioning features or use of this software
#    must display the following acknowledgement:
#    This product includes software developed by the <organization>.
# 4. Neither the name of the <organization> nor the
#    names of its contributors may be used to endorse or promote products
#    derived from this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY <COPYRIGHT HOLDER> ''AS IS'' AND ANY
# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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import StringIO

from matplotlib.backends.backend_agg import FigureCanvasAgg
from matplotlib.figure import Figure
import numpy as np

from kivy.app import App
from kivy.core.image.img_pygame import ImageLoaderPygame
from kivy.properties import ObjectProperty
from kivy.uix.image import Image


def cardioid(start, stop, step):
    """A rotated cardioid."""
    theta = np.arange(start, stop, step)
    r = 1 - np.sin(theta)
    return theta, r


def polar_plot(theta, r, rmax):
    """Draw a polat plot.

    :returns: matplotlib.Figure
    """
    fig = Figure(facecolor='white')
    ax = fig.add_subplot(111, polar=True, frameon=False)
    ax.grid(False)
    ax.set_xticklabels([])
    ax.set_yticklabels([])
    ax.plot(theta, r, color='g', linewidth=2)
    ax.set_rmax(rmax)
    return fig


def fig2png(fig):
    """Convert a matplotlib.Figure to PNG image.

    :returns: PNG image bytes
    """
    data = StringIO.StringIO()
    canvas = FigureCanvasAgg(fig)
    canvas.print_png(data)
    return data.getvalue()


class MemoryImage(Image):
    """Display an image already loaded in memory."""
    memory_data = ObjectProperty(None)

    def __init__(self, memory_data, **kwargs):
        super(MemoryImage, self).__init__(**kwargs)

        self.memory_data = memory_data

    def on_memory_data(self, *args):
        """Load image from memory."""
        data = StringIO.StringIO(self.memory_data)
        with self.canvas:
            self.texture = ImageLoaderPygame(data).texture


class TestApp(App):

    def build(self):
        return MemoryImage(self.options['image'])

if __name__ == '__main__':

    theta, r = cardioid(0, 8.0, 0.01)
    image = fig2png(polar_plot(theta, r, 2.5))
    TestApp(image=image).run()