Add a C file generator for TrueType fonts
In order to be able to optimize the output better, add my own TTF generator. Fortunately, freetype-py handles all of the hard work. The generator is not yet integrated.
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230
gen/font.py
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230
gen/font.py
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#!/usr/bin/env python3
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# -*- coding: utf-8 -*-
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# Needs freetype-py>=1.0
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# For more info see:
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# http://dbader.org/blog/monochrome-font-rendering-with-freetype-and-python
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# The MIT License (MIT)
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#
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# Copyright (c) 2013 Daniel Bader (http://dbader.org)
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# Copyright (c) 2019 Max Regan (http://git.maxregan.me)
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#
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# Permission is hereby granted, free of charge, to any person obtaining a copy
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# of this software and associated documentation files (the "Software"), to deal
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# in the Software without restriction, including without limitation the rights
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# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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# copies of the Software, and to permit persons to whom the Software is
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# furnished to do so, subject to the following conditions:
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#
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# The above copyright notice and this permission notice shall be included in
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# all copies or substantial portions of the Software.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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# THE SOFTWARE.
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import freetype
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class Bitmap(object):
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"""
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A 2D bitmap image represented as a list of byte values. Each byte indicates the state
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of a single pixel in the bitmap. A value of 0 indicates that the pixel is `off`
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and any other value indicates that it is `on`.
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"""
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def __init__(self, width, height, pixels=None):
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self.width = width
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self.height = height
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self.pixels = pixels or bytearray(width * height)
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def __repr__(self):
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"""Return a string representation of the bitmap's pixels."""
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rows = ''
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for y in range(self.height):
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for x in range(self.width):
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rows += '#' if self.pixels[y * self.width + x] else ' '
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rows += '\n'
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return rows
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def bitblt(self, src, x, y):
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"""Copy all pixels from `src` into this bitmap"""
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srcpixel = 0
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dstpixel = y * self.width + x
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row_offset = self.width - src.width
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for sy in range(src.height):
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for sx in range(src.width):
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# Perform an OR operation on the destination pixel and the source pixel
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# because glyph bitmaps may overlap if character kerning is applied, e.g.
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# in the string "AVA", the "A" and "V" glyphs must be rendered with
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# overlapping bounding boxes.
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self.pixels[dstpixel] = self.pixels[dstpixel] or src.pixels[srcpixel]
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srcpixel += 1
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dstpixel += 1
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dstpixel += row_offset
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class Glyph(object):
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def __init__(self, pixels, width, height, top, advance_width):
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self.bitmap = Bitmap(width, height, pixels)
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# The glyph bitmap's top-side bearing, i.e. the vertical distance from the
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# baseline to the bitmap's top-most scanline.
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self.top = top
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# Ascent and descent determine how many pixels the glyph extends
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# above or below the baseline.
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self.descent = max(0, self.height - self.top)
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self.ascent = max(0, max(self.top, self.height) - self.descent)
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# The advance width determines where to place the next character horizontally,
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# that is, how many pixels we move to the right to draw the next glyph.
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self.advance_width = advance_width
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@property
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def width(self):
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return self.bitmap.width
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@property
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def height(self):
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return self.bitmap.height
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@staticmethod
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def from_glyphslot(slot):
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"""Construct and return a Glyph object from a FreeType GlyphSlot."""
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pixels = Glyph.unpack_mono_bitmap(slot.bitmap)
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width, height = slot.bitmap.width, slot.bitmap.rows
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top = slot.bitmap_top
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# The advance width is given in FreeType's 26.6 fixed point format,
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# which means that the pixel values are multiples of 64.
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assert slot.advance.x % 64 == 0
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advance_width = slot.advance.x // 64
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return Glyph(pixels, width, height, top, advance_width)
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@staticmethod
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def unpack_mono_bitmap(bitmap):
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"""
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Unpack a freetype FT_LOAD_TARGET_MONO glyph bitmap into a bytearray where each
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pixel is represented by a single byte.
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"""
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# Allocate a bytearray of sufficient size to hold the glyph bitmap.
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data = bytearray(bitmap.rows * bitmap.width)
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# Iterate over every byte in the glyph bitmap. Note that we're not
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# iterating over every pixel in the resulting unpacked bitmap --
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# we're iterating over the packed bytes in the input bitmap.
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for y in range(bitmap.rows):
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for byte_index in range(bitmap.pitch):
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# Read the byte that contains the packed pixel data.
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byte_value = bitmap.buffer[y * bitmap.pitch + byte_index]
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# We've processed this many bits (=pixels) so far. This determines
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# where we'll read the next batch of pixels from.
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num_bits_done = byte_index * 8
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# Pre-compute where to write the pixels that we're going
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# to unpack from the current byte in the glyph bitmap.
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rowstart = y * bitmap.width + byte_index * 8
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# Iterate over every bit (=pixel) that's still a part of the
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# output bitmap. Sometimes we're only unpacking a fraction of a byte
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# because glyphs may not always fit on a byte boundary. So we make sure
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# to stop if we unpack past the current row of pixels.
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for bit_index in range(min(8, bitmap.width - num_bits_done)):
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# Unpack the next pixel from the current glyph byte.
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bit = byte_value & (1 << (7 - bit_index))
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# Write the pixel to the output bytearray. We ensure that `off`
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# pixels have a value of 0 and `on` pixels have a value of 1.
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data[rowstart + bit_index] = 1 if bit else 0
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return data
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class FixedFont(object):
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def __init__(self, filename, size):
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self.face = freetype.Face(filename)
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self.face.set_pixel_sizes(0, size)
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if not self.face.is_fixed_width:
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raise ValueError("Font is not fixed width")
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self.face.load_char('A', freetype.FT_LOAD_RENDER | freetype.FT_LOAD_TARGET_MONO)
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self.advance = self.face.glyph.advance.x // 64
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def glyph_for_character(self, char):
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# Let FreeType load the glyph for the given character and tell it to render
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# a monochromatic bitmap representation.
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self.face.load_char(char, freetype.FT_LOAD_RENDER | freetype.FT_LOAD_TARGET_MONO)
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return Glyph.from_glyphslot(self.face.glyph)
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def render_character(self, char):
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glyph = self.glyph_for_character(char)
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return glyph.bitmap
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def text_dimensions(self, text):
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"""Return (width, height, baseline) of `text` rendered in the current font."""
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width = 0
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max_ascent = 0
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max_descent = 0
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previous_char = None
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# For each character in the text string we get the glyph
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# and update the overall dimensions of the resulting bitmap.
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for char in text:
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glyph = self.glyph_for_character(char)
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max_ascent = max(max_ascent, glyph.ascent)
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max_descent = max(max_descent, glyph.descent)
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# With kerning, the advance width may be less than the width of the glyph's bitmap.
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# Make sure we compute the total width so that all of the glyph's pixels
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# fit into the returned dimensions.
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width += self.advance
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previous_char = char
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height = max_ascent + max_descent
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return (width, height, max_descent)
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def render_text(self, text, width=None, height=None, baseline=None):
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"""
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Render the given `text` into a Bitmap and return it.
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If `width`, `height`, and `baseline` are not specified they are computed using
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the `text_dimensions' method.
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"""
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if None in (width, height, baseline):
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width, height, baseline = self.text_dimensions(text)
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x = 0
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previous_char = None
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outbuffer = Bitmap(width, height)
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for char in text:
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glyph = self.glyph_for_character(char)
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# The vertical drawing position should place the glyph
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# on the baseline as intended.
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y = height - glyph.ascent - baseline
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outbuffer.bitblt(glyph.bitmap, x, y)
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x += glyph.advance_width
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previous_char = char
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return outbuffer
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if __name__ == '__main__':
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# Be sure to place 'helvetica.ttf' (or any other ttf / otf font file) in the working directory.
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fnt = FixedFont('/usr/share/fonts/truetype/ubuntu/UbuntuMono-R.ttf', 24)
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print(repr(fnt.render_text('AV Wa')))
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