hatch.py

"""
Contains a classes for generating hatch patterns.
"""

import numpy as np
from matplotlib.path import Path


class HatchPatternBase:
    """
    The base class for a hatch pattern.
    """
    pass


class HorizontalHatch(HatchPatternBase):
    def __init__(self, hatch, density):
        self.num_lines = int((hatch.count('-') + hatch.count('+')) * density)
        self.num_vertices = self.num_lines * 2

    def set_vertices_and_codes(self, vertices, codes):
        steps, stepsize = np.linspace(0.0, 1.0, self.num_lines, False,
                                      retstep=True)
        steps += stepsize / 2.
        vertices[0::2, 0] = 0.0
        vertices[0::2, 1] = steps
        vertices[1::2, 0] = 1.0
        vertices[1::2, 1] = steps
        codes[0::2] = Path.MOVETO
        codes[1::2] = Path.LINETO


class VerticalHatch(HatchPatternBase):
    def __init__(self, hatch, density):
        self.num_lines = int((hatch.count('|') + hatch.count('+')) * density)
        self.num_vertices = self.num_lines * 2

    def set_vertices_and_codes(self, vertices, codes):
        steps, stepsize = np.linspace(0.0, 1.0, self.num_lines, False,
                                      retstep=True)
        steps += stepsize / 2.
        vertices[0::2, 0] = steps
        vertices[0::2, 1] = 0.0
        vertices[1::2, 0] = steps
        vertices[1::2, 1] = 1.0
        codes[0::2] = Path.MOVETO
        codes[1::2] = Path.LINETO


class NorthEastHatch(HatchPatternBase):
    def __init__(self, hatch, density):
        self.num_lines = int((hatch.count('/') + hatch.count('x') +
                          hatch.count('X')) * density)
        if self.num_lines:
            self.num_vertices = (self.num_lines + 1) * 2
        else:
            self.num_vertices = 0

    def set_vertices_and_codes(self, vertices, codes):
        steps = np.linspace(-0.5, 0.5, self.num_lines + 1)
        vertices[0::2, 0] = 0.0 + steps
        vertices[0::2, 1] = 0.0 - steps
        vertices[1::2, 0] = 1.0 + steps
        vertices[1::2, 1] = 1.0 - steps
        codes[0::2] = Path.MOVETO
        codes[1::2] = Path.LINETO


class SouthEastHatch(HatchPatternBase):
    def __init__(self, hatch, density):
        self.num_lines = int((hatch.count('\\') + hatch.count('x') +
                          hatch.count('X')) * density)
        self.num_vertices = (self.num_lines + 1) * 2
        if self.num_lines:
            self.num_vertices = (self.num_lines + 1) * 2
        else:
            self.num_vertices = 0

    def set_vertices_and_codes(self, vertices, codes):
        steps = np.linspace(-0.5, 0.5, self.num_lines + 1)
        vertices[0::2, 0] = 0.0 + steps
        vertices[0::2, 1] = 1.0 + steps
        vertices[1::2, 0] = 1.0 + steps
        vertices[1::2, 1] = 0.0 + steps
        codes[0::2] = Path.MOVETO
        codes[1::2] = Path.LINETO


class Shapes(HatchPatternBase):
    filled = False

    def __init__(self, hatch, density):
        if self.num_rows == 0:
            self.num_shapes = 0
            self.num_vertices = 0
        else:
            self.num_shapes = ((self.num_rows // 2 + 1) * (self.num_rows + 1) +
                               (self.num_rows // 2) * (self.num_rows))
            self.num_vertices = (self.num_shapes *
                                 len(self.shape_vertices) *
                                 (1 if self.filled else 2))

    def set_vertices_and_codes(self, vertices, codes):
        offset = 1.0 / self.num_rows
        shape_vertices = self.shape_vertices * offset * self.size
        if not self.filled:
            inner_vertices = shape_vertices[::-1] * 0.9
        shape_codes = self.shape_codes
        shape_size = len(shape_vertices)

        cursor = 0
        for row in range(self.num_rows + 1):
            if row % 2 == 0:
                cols = np.linspace(0, 1, self.num_rows + 1)
            else:
                cols = np.linspace(offset / 2, 1 - offset / 2, self.num_rows)
            row_pos = row * offset
            for col_pos in cols:
                vertices[cursor:cursor + shape_size] = (shape_vertices +
                                                        (col_pos, row_pos))
                codes[cursor:cursor + shape_size] = shape_codes
                cursor += shape_size
                if not self.filled:
                    vertices[cursor:cursor + shape_size] = (inner_vertices +
                                                            (col_pos, row_pos))
                    codes[cursor:cursor + shape_size] = shape_codes
                    cursor += shape_size


class Circles(Shapes):
    def __init__(self, hatch, density):
        path = Path.unit_circle()
        self.shape_vertices = path.vertices
        self.shape_codes = path.codes
        Shapes.__init__(self, hatch, density)


class SmallCircles(Circles):
    size = 0.2

    def __init__(self, hatch, density):
        self.num_rows = (hatch.count('o')) * density
        Circles.__init__(self, hatch, density)


class LargeCircles(Circles):
    size = 0.35

    def __init__(self, hatch, density):
        self.num_rows = (hatch.count('O')) * density
        Circles.__init__(self, hatch, density)


class SmallFilledCircles(SmallCircles):
    size = 0.1
    filled = True

    def __init__(self, hatch, density):
        self.num_rows = (hatch.count('.')) * density
        Circles.__init__(self, hatch, density)


class Stars(Shapes):
    size = 1.0 / 3.0
    filled = True

    def __init__(self, hatch, density):
        self.num_rows = (hatch.count('*')) * density
        path = Path.unit_regular_star(5)
        self.shape_vertices = path.vertices
        self.shape_codes = np.full(len(self.shape_vertices), Path.LINETO,
                                   dtype=Path.code_type)
        self.shape_codes[0] = Path.MOVETO
        Shapes.__init__(self, hatch, density)

_hatch_types = [
    HorizontalHatch,
    VerticalHatch,
    NorthEastHatch,
    SouthEastHatch,
    SmallCircles,
    LargeCircles,
    SmallFilledCircles,
    Stars
    ]


def get_path(hatchpattern, density=6):
    """
    Given a hatch specifier, *hatchpattern*, generates Path to render
    the hatch in a unit square.  *density* is the number of lines per
    unit square.
    """
    density = int(density)

    patterns = [hatch_type(hatchpattern, density)
                for hatch_type in _hatch_types]
    num_vertices = sum([pattern.num_vertices for pattern in patterns])

    if num_vertices == 0:
        return Path(np.empty((0, 2)))

    vertices = np.empty((num_vertices, 2))
    codes = np.empty(num_vertices, Path.code_type)

    cursor = 0
    for pattern in patterns:
        if pattern.num_vertices != 0:
            vertices_chunk = vertices[cursor:cursor + pattern.num_vertices]
            codes_chunk = codes[cursor:cursor + pattern.num_vertices]
            pattern.set_vertices_and_codes(vertices_chunk, codes_chunk)
            cursor += pattern.num_vertices

    return Path(vertices, codes)