Rendering outlined font with FT2 + PIL

outline-char.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# outline-char.py: POC of rendering outlined font with FT2 + PIL. 
#
# Copyright (C) 2011 Takahiro Yoshimura <taky@cs.monolithworks.co.jp>
#
# 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/>.

import struct
import freetype
import Image, ImageDraw

class FT2Bitmap(object):
    def __init__(self, bitmap):
        self.bitmap = bitmap

    def to_pil_image(self):
        data = ''.join([struct.pack('B', c) for c in self.bitmap.buffer])
        return Image.frombuffer("L", (self.bitmap.width, self.bitmap.rows), data, "raw", "L", 0, 1)

class OutlinedGlyphWriter(object):
    def __init__(self, char, face, size, outline, outline_color):
        self.char = char
        self.face_name = face
        self.char_size = size
        self.outline_width = outline
        self.outline_color = outline_color
        
    def write(self):
        mask = self._write_glyph()
        im = Image.new('RGBA', mask.size, (0,0,0,255))
        draw = ImageDraw.Draw(im)
        draw.bitmap((0, 0), mask, self.outline_color)
        return im

    def _load_glyph(self):
        face = freetype.Face(self.face_name)
        face.set_char_size(self.char_size * 64)
        face.load_char(self.char, freetype.FT_LOAD_DEFAULT | freetype.FT_LOAD_NO_BITMAP)
        return face.glyph.get_glyph()

    def _write_base(self):
        glyph = self._load_glyph()
        stroker = freetype.Stroker()
        stroker.set(self.outline_width * 64, freetype.FT_STROKER_LINECAP_ROUND, freetype.FT_STROKER_LINEJOIN_ROUND, 0 )
        glyph.stroke(stroker)
        bitmap = glyph.to_bitmap(freetype.FT_RENDER_MODE_NORMAL, freetype.Vector(0,0)).bitmap 
        return FT2Bitmap(bitmap).to_pil_image()

    def _write_glyph(self):
        base = self._write_base()
        glyph = self._load_glyph()
        bitmap = glyph.to_bitmap(freetype.FT_RENDER_MODE_NORMAL, freetype.Vector(0,0)).bitmap 
        mask = FT2Bitmap(bitmap).to_pil_image()
        draw = ImageDraw.Draw(base)
        draw.bitmap((self.outline_width, self.outline_width), mask, 0)
        return base

if __name__ == '__main__':
    face_name = u'./fonts/ヒラギノ角ゴ Std W6.otf'.encode('utf-8')
    glyph_size = 1024
    outline_width = 64
    outline_color = (255,255,255,255)

    char = u'あ'
    im = OutlinedGlyphWriter(char, face_name, glyph_size, outline_width, outline_color).write()
    im.show()
    im.save('hoge.png', 'png')