Source code for pymor.analyticalproblems.text

# This file is part of the pyMOR project (http://www.pymor.org).
# Copyright 2013-2020 pyMOR developers and contributors. All rights reserved.
# License: BSD 2-Clause License (http://opensource.org/licenses/BSD-2-Clause)

from pymor.analyticalproblems.domaindescriptions import RectDomain
from pymor.analyticalproblems.elliptic import StationaryProblem
from pymor.analyticalproblems.functions import ConstantFunction, LincombFunction, BitmapFunction
from pymor.core.defaults import defaults
from pymor.parameters.functionals import ProjectionParameterFunctional


@defaults('font_name')
def text_problem(text='pyMOR', font_name=None):
    import numpy as np
    from PIL import Image, ImageDraw, ImageFont
    from tempfile import NamedTemporaryFile

    font_list = [font_name] if font_name else ['DejaVuSansMono.ttf', 'VeraMono.ttf', 'UbuntuMono-R.ttf', 'Arial.ttf']
    font = None
    for filename in font_list:
        try:
            font = ImageFont.truetype(filename, 64)  # load some font from file of given size
        except (OSError, IOError):
            pass
    if font is None:
        raise ValueError('Could not load TrueType font')

    size = font.getsize(text)                             # compute width and height of rendered text
    size = (size[0] + 20, size[1] + 20)                   # add a border of 10 pixels around the text

    def make_bitmap_function(char_num):                   # we need to genereate a BitmapFunction for each character
        img = Image.new('L', size)                        # create new Image object of given dimensions
        d = ImageDraw.Draw(img)                           # create ImageDraw object for the given Image

        # in order to position the character correctly, we first draw all characters from the first
        # up to the wanted character
        d.text((10, 10), text[:char_num + 1], font=font, fill=255)

        # next we erase all previous character by drawing a black rectangle
        if char_num > 0:
            d.rectangle(((0, 0), (font.getsize(text[:char_num])[0] + 10, size[1])), fill=0, outline=0)

        # open a new temporary file
        with NamedTemporaryFile(suffix='.png') as f:    # after leaving this 'with' block, the temporary
                                                        # file is automatically deleted
            img.save(f, format='png')
            return BitmapFunction(f.name, bounding_box=[(0, 0), size], range=[0., 1.])

    # create BitmapFunctions for each character
    dfs = [make_bitmap_function(n) for n in range(len(text))]

    # create an indicator function for the background
    background = ConstantFunction(1., 2) - LincombFunction(dfs, np.ones(len(dfs)))

    # form the linear combination
    dfs = [background] + dfs
    coefficients = [1] + [ProjectionParameterFunctional('diffusion', len(text), i) for i in range(len(text))]
    diffusion = LincombFunction(dfs, coefficients)

    return StationaryProblem(
        domain=RectDomain(dfs[1].bounding_box, bottom='neumann'),
        neumann_data=ConstantFunction(-1., 2),
        diffusion=diffusion,
        parameter_ranges=(0.1, 1.)
    )