#!/usr/bin/env python3 # -*- coding: utf-8 -*- # Needs freetype-py>=1.0 # For more info see: # http://dbader.org/blog/monochrome-font-rendering-with-freetype-and-python # The MIT License (MIT) # # Copyright (c) 2013 Daniel Bader (http://dbader.org) # Copyright (c) 2019 Max Regan (http://git.maxregan.me) # # 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 freetype class Bitmap(object): """ 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 = width self.height = 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 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 sy in range(src.height): for sx 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(object): def __init__(self, pixels, width, height, top, 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 # 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 # The advance width is given in FreeType's 26.6 fixed point format, # which means that the pixel values are multiples of 64. assert slot.advance.x % 64 == 0 advance_width = slot.advance.x // 64 return Glyph(pixels, width, height, top, 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 FixedFont(object): def __init__(self, filename, size): self.face = freetype.Face(filename) self.face.set_pixel_sizes(0, size) if not self.face.is_fixed_width: raise ValueError("Font is not fixed width") self.face.load_char('A', freetype.FT_LOAD_RENDER | freetype.FT_LOAD_TARGET_MONO) self.advance = self.face.glyph.advance.x // 64 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 previous_char = None # 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) # With kerning, the advance width may be less than the width of the glyph's bitmap. # Make sure we compute the total width so that all of the glyph's pixels # fit into the returned dimensions. width += self.advance previous_char = char height = max_ascent + max_descent return (width, height, max_descent) def render_text(self, text, width=None, height=None, baseline=None): """ Render the given `text` into a Bitmap and return it. If `width`, `height`, and `baseline` are not specified they are computed using the `text_dimensions' method. """ if None in (width, height, baseline): width, height, baseline = self.text_dimensions(text) x = 0 previous_char = None outbuffer = Bitmap(width, height) for char in text: glyph = self.glyph_for_character(char) # The vertical drawing position should place the glyph # on the baseline as intended. y = height - glyph.ascent - baseline outbuffer.bitblt(glyph.bitmap, x, y) x += glyph.advance_width previous_char = char return outbuffer if __name__ == '__main__': # Be sure to place 'helvetica.ttf' (or any other ttf / otf font file) in the working directory. fnt = FixedFont('/usr/share/fonts/truetype/ubuntu/UbuntuMono-R.ttf', 24) print(repr(fnt.render_text('AV Wa')))