Source code for bdflib.effects

# bdflib, a library for working with BDF font files
# Copyright (C) 2009-2022, Timothy Allen
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

"""
Automatically generate visual variants of a font.
"""


def embolden(font, maintain_spacing=True):
    """
    Create a bold version of a font by widening each glyph.

    :param Font font: The font to embolden.
    :param bool maintain_spacing: If true, each glyph's advance width
            will be incremented, because a wider glyph needs more room.
    :returns: A copy of ``font``, with each glyph emboldened.
    :rtype: :class:`.Font`

    To embolden a glyph, it is drawn over itself one pixel to the right,
    making each vertical stroke one pixel wider.
    """
    res = font.copy()

    for cp in res.codepoints():
        g = res[cp]
        g.merge_glyph(g, 1, 0)
        if maintain_spacing:
            g.advance += 1

    return res


def merge(base, custom):
    """
    Create a new font by choosing glyphs from two other fonts.

    :param Font base: The lower-priority font.
    :param Font custom: The higher-priority font.
    :returns: A font where each glyph comes from ``base`` or ``custom``.

    For any given codepoint, the resulting font will use the corresponding
    glyph from ``custom`` if there is one, falling back to the glyph from
    ``base``. The new font's properties and other metadata are all copied
    from ``custom``.
    """
    res = custom.copy()

    for cp in base.codepoints():
        if cp not in res:
            old_glyph = base[cp]
            res.new_glyph_from_data(
                old_glyph.name,
                old_glyph.data,
                old_glyph.bbX,
                old_glyph.bbY,
                old_glyph.bbW,
                old_glyph.bbH,
                old_glyph.advance,
                old_glyph.codepoint,
            )

    return res