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add font utils

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kicer
2026-01-25 15:14:15 +08:00
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#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# Needs freetype-py>=1.0
# Font handling classes are from Dan Bader blog post on using freetype
# http://dbader.org/blog/monochrome-font-rendering-with-freetype-and-python
#
# Modified by Russ Hughes, Mar 2021 to write bitmap modules compatible with
# the MicroPython ili9342c driver at https://github.com/russhughes/ili9342c_mpy
# and the st7789 driver at https://github.com/russhughes/st7789_mpy.
#
# The Negative glyph.left fix is from peterhinch's font conversion program
# https://github.com/peterhinch/micropython-font-to-py
# https://github.com/peterhinch/micropython-font-to-py/issues/21
# Handle negative glyph.left correctly (capital J),
# also glyph.width > advance (capital K and R).
#
# The MIT License (MIT)
#
# Copyright (c) 2013 Daniel Bader (http://dbader.org)
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
import sys
import shlex
import argparse
import bisect
import freetype
def to_int(string):
""" Return integer value from a hex or decimal string"""
return int(string, base=16) if string.startswith("0x") else int(string)
def get_chars(string):
""" Return string comprised of given characters or range(s) of characters"""
return ''.join(chr(b) for a in [
(lambda sub: range(sub[0], sub[-1] + 1))
(list(map(to_int, ele.split('-'))))
for ele in string.split(',')] for b in a)
def wrap_str(string, items_per_line=32):
""" Return a string wrapped to items_per_line with special care for escape characters"""
length = len(string)
lines = []
i = 0
end = 0
while length > end:
end = min(i + items_per_line, length)
if string[end - 1] == '\\':
end -= 2
lines.append(string[i : end])
i = end
return "(\n '" + "'\n '".join(lines) + "'\n)"
def wrap_bytes(lst, items_per_line=16):
"""Return a string of items wrapped to items_per_line"""
lines = [
"".join(f'\\x{x:02x}' for x in lst[i : i + items_per_line])
for i in range(0, len(lst), items_per_line)
]
return " b'" + "'\\\n b'".join(lines) + "'"
def wrap_longs(lst, items_per_line=16):
"""Return a string of longs wrapped to items_per_line"""
lines = [
"".join(f'\\x{x:02x}' for x in lst[i : i + items_per_line])
for i in range(0, len(lst), items_per_line)
]
return " b'" + "'\\\n b'".join(lines) + "'"
class Bitmap():
"""
A 2D bitmap image represented as a list of byte values. Each byte indicates
the state of a single pixel in the bitmap. A value of 0 indicates that the
pixel is `off` and any other value indicates that it is `on`.
"""
def __init__(self, width, height, pixels=None):
self.width = int(width)
self.height = int(height)
self.pixels = pixels or bytearray(width * height)
def __repr__(self):
"""Return a string representation of the bitmap's pixels."""
rows = ''
for y in range(self.height):
for x in range(self.width):
rows += '#' if self.pixels[y * self.width + x] else '.'
rows += '\n'
return rows
def bit_string(self):
"""Return a binary string representation of the bitmap's pixels."""
bits = ''
for y in range(self.height):
for x in range(self.width):
bits += '1' if self.pixels[y * self.width + x] else '0'
return bits
def bitblt(self, src, x, y):
"""Copy all pixels from `src` into this bitmap"""
srcpixel = 0
dstpixel = y * self.width + x
row_offset = self.width - src.width
for _ in range(src.height):
for _ in range(src.width):
# Perform an OR operation on the destination pixel and the
# source pixel because glyph bitmaps may overlap if character
# kerning is applied, e.g. in the string "AVA", the "A" and "V"
# glyphs must be rendered with overlapping bounding boxes.
self.pixels[dstpixel] = (
self.pixels[dstpixel] or src.pixels[srcpixel])
srcpixel += 1
dstpixel += 1
dstpixel += row_offset
class Glyph():
def __init__(self, pixels, width, height, top, left, advance_width):
self.bitmap = Bitmap(width, height, pixels)
# The glyph bitmap's top-side bearing, i.e. the vertical distance from
# the baseline to the bitmap's top-most scanline.
self.top = top
self.left = left
# Ascent and descent determine how many pixels the glyph extends
# above or below the baseline.
self.descent = max(0, self.height - self.top)
self.ascent = max(0, max(self.top, self.height) - self.descent)
# The advance width determines where to place the next character
# horizontally, that is, how many pixels we move to the right to draw
# the next glyph.
self.advance_width = advance_width
@property
def width(self):
return self.bitmap.width
@property
def height(self):
return self.bitmap.height
@staticmethod
def from_glyphslot(slot):
"""Construct and return a Glyph object from a FreeType GlyphSlot."""
pixels = Glyph.unpack_mono_bitmap(slot.bitmap)
width, height = slot.bitmap.width, slot.bitmap.rows
top = slot.bitmap_top
left = slot.bitmap_left
# The advance width is given in FreeType's 26.6 fixed point format,
# which means that the pixel values are multiples of 64.
advance_width = slot.advance.x // 64
return Glyph(pixels, width, height, top, left, advance_width)
@staticmethod
def unpack_mono_bitmap(bitmap):
"""
Unpack a freetype FT_LOAD_TARGET_MONO glyph bitmap into a bytearray
where each pixel is represented by a single byte.
"""
# Allocate a bytearray of sufficient size to hold the glyph bitmap.
data = bytearray(bitmap.rows * bitmap.width)
# Iterate over every byte in the glyph bitmap. Note that we're not
# iterating over every pixel in the resulting unpacked bitmap --
# we're iterating over the packed bytes in the input bitmap.
for y in range(bitmap.rows):
for byte_index in range(bitmap.pitch):
# Read the byte that contains the packed pixel data.
byte_value = bitmap.buffer[y * bitmap.pitch + byte_index]
# We've processed this many bits (=pixels) so far. This
# determines where we'll read the next batch of pixels from.
num_bits_done = byte_index * 8
# Pre-compute where to write the pixels that we're going
# to unpack from the current byte in the glyph bitmap.
rowstart = y * bitmap.width + byte_index * 8
# Iterate over every bit (=pixel) that's still a part of the
# output bitmap. Sometimes we're only unpacking a fraction of a
# byte because glyphs may not always fit on a byte boundary. So
# we make sure to stop if we unpack past the current row of
# pixels.
for bit_index in range(min(8, bitmap.width - num_bits_done)):
# Unpack the next pixel from the current glyph byte.
bit = byte_value & (1 << (7 - bit_index))
# Write the pixel to the output bytearray. We ensure that
# `off` pixels have a value of 0 and `on` pixels have a
# value of 1.
data[rowstart + bit_index] = 1 if bit else 0
return data
class Font():
def __init__(self, filename, width, height):
self.face = freetype.Face(filename)
self.face.set_pixel_sizes(width, height)
def glyph_for_character(self, char):
# Let FreeType load the glyph for the given character and tell it to
# render a monochromatic bitmap representation.
self.face.load_char(
char, freetype.FT_LOAD_RENDER | freetype.FT_LOAD_TARGET_MONO)
return Glyph.from_glyphslot(self.face.glyph)
def render_character(self, char):
glyph = self.glyph_for_character(char)
return glyph.bitmap
def text_dimensions(self, text):
"""
Return (width, height, baseline) of `text` rendered in the current
font.
"""
width = 0
max_ascent = 0
max_descent = 0
# For each character in the text string we get the glyph
# and update the overall dimensions of the resulting bitmap.
for char in text:
glyph = self.glyph_for_character(char)
max_ascent = max(max_ascent, glyph.ascent)
max_descent = max(max_descent, glyph.descent)
if glyph.left >= 0:
char_width = int(
max(glyph.advance_width, glyph.width + glyph.left))
else:
char_width = int(
max(glyph.advance_width - glyph.left, glyph.width))
width += char_width
height = max_ascent + max_descent
return (width, height, max_descent)
def write_python(self, text, font_file):
"""
Render the given `text` into a python bitmap module.
"""
_, height, baseline = self.text_dimensions(text)
bits = []
widths = []
offsets = []
offset = 0
for char in text:
glyph = self.glyph_for_character(char)
# Negative glyph.left fix from peterhinch
# https://github.com/peterhinch/micropython-font-to-py
#
# https://github.com/peterhinch/micropython-font-to-py/issues/21
# Handle negative glyph.left correctly (capital J),
# also glyph.width > advance (capital K and R).
if glyph.left >= 0:
char_width = int(
max(glyph.advance_width, glyph.width + glyph.left))
left = glyph.left
else:
char_width = int(
max(glyph.advance_width - glyph.left, glyph.width))
left = 0
# save the bit offset and width of the current glyph
offsets.append(offset)
widths.append(char_width)
outbuffer = Bitmap(char_width, height)
# The vertical drawing position should place the glyph
# on the baseline as intended.
y = height - glyph.ascent - baseline
outbuffer.bitblt(glyph.bitmap, left, y)
# convert bitmap to ascii bitmap string
bit_string = outbuffer.bit_string()
bits.append(bit_string)
offset += len(bit_string)
# join all the bitmap strings together
bit_string = ''.join(bits)
# escape backslash, quote and single quote characters for char_map
text_escaped = text.replace('\\', '\\\\').replace('"', '\\"').replace("'", "\\'")
char_map = wrap_str(text_escaped)
cmd_line = " ".join(map(shlex.quote, sys.argv))
max_width = max(widths)
# write python module source
print('# -*- coding: utf-8 -*-')
print(f'# Converted from {font_file} using:')
print(f'# {cmd_line}')
print()
print(f'MAP = {char_map}\n')
print('BPP = 1')
print(f'HEIGHT = {height}')
print(f'MAX_WIDTH = {max_width}')
print('_WIDTHS = \\')
print(wrap_bytes(widths))
print()
byte_offsets = bytearray()
bytes_table = [0xff, 0xffff, 0xffffff, 0xffffffff]
bytes_required = bisect.bisect_left(bytes_table, offset, 0, 3) + 1
for offset in offsets:
byte_offsets.extend(offset.to_bytes(bytes_required, 'big'))
print(f'OFFSET_WIDTH = {bytes_required}')
print('_OFFSETS = \\')
print(wrap_longs(byte_offsets))
print()
print('_BITMAPS =\\')
byte_values = [int(bit_string[i:i+8], 2) for i in range(0, len(bit_string), 8)]
print(wrap_bytes(byte_values))
print("\nWIDTHS = memoryview(_WIDTHS)")
print("OFFSETS = memoryview(_OFFSETS)")
print("BITMAPS = memoryview(_BITMAPS)")
def main():
parser = argparse.ArgumentParser(
prog='font2bitmap',
description=('''
Convert characters from a truetype font to a python bitmap for use
with the bitmap method in the st7789 and ili9342 drivers.'''))
parser.add_argument(
'font_file',
help='name of font file to convert.')
parser.add_argument(
'font_height',
type=int,
default=8,
help='size of font to create bitmaps from.')
parser.add_argument(
'-width', '--font_width',
type=int,
default=None,
help='width of font to create bitmaps from.')
group = parser.add_argument_group(
'character selection',
'characters from the font to include in the bitmap.')
excl = group.add_mutually_exclusive_group(required=True)
excl.add_argument(
'-c', '--characters',
help='''integer or hex character values and/or ranges to include.
For example: "65, 66, 67" or "32-127" or "0x30-0x39, 0x41-0x5a"''')
excl.add_argument(
'-s', '--string',
help='''string of characters to include
For example: "1234567890-."''')
args = parser.parse_args()
font_file = args.font_file
height = args.font_height
width = args.font_height if args.font_width is None else args.font_width
characters = get_chars(args.characters) if args.string is None else args.string
fnt = Font(font_file, width, height)
fnt.write_python(characters, font_file)
main()