build.py

#!/usr/bin/env python
# Copyright (c) 2013 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
"""Script to generate bitmaps for firmware screens."""

import argparse
from collections import defaultdict, namedtuple
import copy
import glob
import json
import multiprocessing
import os
import re
import shutil
import signal
import subprocess
import sys
import tempfile
from xml.etree import ElementTree

import yaml
from PIL import Image

SCRIPT_BASE = os.path.dirname(os.path.abspath(__file__))

STRINGS_GRD_FILE = 'firmware_strings.grd'
STRINGS_JSON_FILE_TMPL = '{}.json'
FORMAT_FILE = 'format.yaml'
BOARDS_CONFIG_FILE = 'boards.yaml'

TXT_TO_PNG_SVG = os.path.join(SCRIPT_BASE, 'text_to_png_svg')
STRINGS_DIR = os.path.join(SCRIPT_BASE, 'strings')
LOCALE_DIR = os.path.join(STRINGS_DIR, 'locale')
OUTPUT_DIR = os.getenv('OUTPUT', os.path.join(SCRIPT_BASE, 'build'))
STAGE_DIR = os.path.join(OUTPUT_DIR, '.stage')
STAGE_LOCALE_DIR = os.path.join(STAGE_DIR, 'locale')
STAGE_FONT_DIR = os.path.join(STAGE_DIR, 'font')

ONE_LINE_DIR = 'one_line'
SVG_FILES = '*.svg'
PNG_FILES = '*.png'

# String format YAML key names.
DEFAULT_NAME = '_DEFAULT_'
KEY_LOCALES = 'locales'
KEY_FILES = 'files'
KEY_FONTS = 'fonts'
KEY_STYLES = 'styles'
DIAGNOSTIC_FILES = 'diagnostic_files'

# Board config YAML key names.
SCREEN_KEY = 'screen'
PANEL_KEY = 'panel'
SDCARD_KEY = 'sdcard'
BAD_USB3_KEY = 'bad_usb3'
LOCALES_KEY = 'locales'
RTL_KEY = 'rtl'
HI_RES_KEY = 'hi_res'
TEXT_COLORS_KEY = 'text_colors'
RW_OVERRIDE_KEY = 'rw_override'

BMP_HEADER_OFFSET_NUM_LINES = 6

# Regular expressions used to eliminate spurious spaces and newlines in
# translation strings.
NEWLINE_PATTERN = re.compile(r'([^\n])\n([^\n])')
NEWLINE_REPLACEMENT = r'\1 \2'
CRLF_PATTERN = re.compile(r'\r\n')
MULTIBLANK_PATTERN = re.compile(r'   *')

GLYPH_FONT = 'Noto Sans Mono'

LocaleInfo = namedtuple('LocaleInfo', ['code', 'rtl', 'hi_res'])


class DataError(Exception):
  pass


class BuildImageError(Exception):
  """The exception class for all errors generated during build image process."""


# Some of the numbers below are from depthcharge:
# - 1000: UI_SCALE
# - 50: UI_MARGIN_H
# - 228: UI_REC_QR_SIZE
# - 24: UI_REC_QR_MARGIN_H
# - 24: UI_DESC_TEXT_HEIGHT
# - 128: UI_FOOTER_HEIGHT
# - 20: UI_FOOTER_COL1_MARGIN_RIGHT
# - 282: width of rec_url.bmp
# - 40: UI_FOOTER_COL2_MARGIN_RIGHT
# - 40: UI_FOOTER_COL3_MARGIN_LEFT
# - 20: UI_FOOTER_TEXT_HEIGHT

DEFAULT_MAX_WIDTH = 1000 - 50 * 2

MAX_WIDTH_LOOKUPS = [
    (re.compile(r'rec_phone_step2_desc'), DEFAULT_MAX_WIDTH - 228 - 24 * 2, 24),
    (re.compile(r'navigate\w*'), DEFAULT_MAX_WIDTH - 128 - 20 - 282 - 40 - 40,
     20),
    (re.compile(r'\w+_desc\w*'), DEFAULT_MAX_WIDTH, 24),
]


def convert_text_to_png(locale, input_file, font, margin, output_dir,
                        options=None):
  """Converts text files into PNG image files.

  Args:
    locale: Locale (language) to select implicit rendering options. None for
      locale-independent strings.
    input_file: Path of input text file.
    font: Font spec.
    margin: CSS-style margin.
    output_dir: Directory to generate image files.
    options: List of other options to be added.
  """
  name, _ = os.path.splitext(os.path.basename(input_file))
  command = [TXT_TO_PNG_SVG, '--outdir=%s' % output_dir]
  if locale:
    command.append('--lan=%s' % locale)
  if font:
    command.append("--font='%s'" % font)
  font_size = os.getenv('FONT_SIZE')
  if font_size:
    command.append('--point=%r' % font_size)
  if margin:
    command.append('--margin="%s"' % margin)
  # TODO(b/159399377): Set different widths for titles and descriptions.
  # Currently only wrap lines for descriptions and navigation instructions in
  # the footer.
  # Without the --width option set, the minimum height of the output SVG
  # image is roughly 22px (for locale 'en'). With --width=WIDTH passed to
  # pango-view, the width of the output seems to always be (WIDTH * 4 / 3),
  # regardless of the font being used. Therefore, set the max_width in
  # points as follows to prevent drawing from exceeding canvas boundary in
  # depthcharge runtime.

  for pattern, max_width, text_height in MAX_WIDTH_LOOKUPS:
    if pattern.fullmatch(name):
      max_width_pt = int(22 * max_width / text_height / (4 / 3))
      command.append('--width=%d' % max_width_pt)
      break

  if options:
    command.extend(options)
  command.append(input_file)

  return subprocess.call(' '.join(command), shell=True,
                         stdout=subprocess.PIPE) == 0


def convert_glyphs():
  """Converts glyphs of ascii characters."""
  os.makedirs(STAGE_FONT_DIR, exist_ok=True)
  # Remove the extra whitespace at the top/bottom within the glyphs
  margin = '-3 0 -1 0'
  options = ['--color="#ffffff"', '--bgcolor="#000000"']
  for c in range(ord(' '), ord('~') + 1):
    txt_file = os.path.join(STAGE_FONT_DIR, f'idx{c:03d}_{c:02x}.txt')
    with open(txt_file, 'w', encoding='ascii') as f:
      f.write(chr(c))
      f.write('\n')
    # TODO(b/163109632): Parallelize the conversion of glyphs
    convert_text_to_png(None, txt_file, GLYPH_FONT, margin, STAGE_FONT_DIR,
                        options)


def _load_locale_json_file(locale, json_dir):
  result = {}
  filename = os.path.join(json_dir, STRINGS_JSON_FILE_TMPL.format(locale))
  with open(filename, encoding='utf-8-sig') as input_file:
    for tag, msgdict in json.load(input_file).items():
      msgtext = msgdict['message']
      msgtext = re.sub(CRLF_PATTERN, '\n', msgtext)
      msgtext = re.sub(NEWLINE_PATTERN, NEWLINE_REPLACEMENT, msgtext)
      msgtext = re.sub(MULTIBLANK_PATTERN, ' ', msgtext)
      # Strip any trailing whitespace.  A trailing newline appears to make
      # Pango report a larger layout size than what's actually visible.
      msgtext = msgtext.strip()
      result[tag] = msgtext
  return result


def parse_locale_json_file(locale, json_dir):
  """Parses given firmware string json file for build_text_files.

  Args:
    locale: The name of the locale, e.g. "da" or "pt-BR".
    json_dir: Directory containing json output from grit.

  Returns:
    A dictionary for mapping of "name to content" for files to be generated.
  """
  result = _load_locale_json_file(locale, json_dir)
  original = _load_locale_json_file('en', json_dir)
  for tag in original:
    if tag not in result:
      # Use original English text, in case translation is not yet available
      print('WARNING: locale "%s", missing entry %s' % (locale, tag))
      result[tag] = original[tag]

  return result


def parse_locale_input_files(locale, json_dir):
  """Parses all firmware string files for the given locale.

  Args:
    locale: The name of the locale, e.g. "da" or "pt-BR".
    json_dir: Directory containing json output from grit.

  Returns:
    A dictionary for mapping of "name to content" for files to be generated.
  """
  result = parse_locale_json_file(locale, json_dir)

  # Walk locale directory to add pre-generated texts such as language names.
  for input_file in glob.glob(os.path.join(LOCALE_DIR, locale, "*.txt")):
    name, _ = os.path.splitext(os.path.basename(input_file))
    with open(input_file, 'r', encoding='utf-8-sig') as f:
      result[name] = f.read().strip()

  return result


def create_file(file_name, contents, output_dir):
  """Creates a text file in output directory by given contents.

  Args:
    file_name: Output file name without extension.
    contents: A list of strings for file content.
    output_dir: The directory to store output file.
  """
  output_name = os.path.join(output_dir, file_name + '.txt')
  with open(output_name, 'w', encoding='utf-8-sig') as f:
    f.write('\n'.join(contents) + '\n')


def build_text_files(inputs, files, output_dir):
  """Builds text files from given input data.

  Args:
    inputs: Dictionary of contents for given file name.
    files: List of file records: [name, content].
    output_dir: Directory to generate text files.
  """
  for file_name, file_content in files.items():
    if file_content is None:
      create_file(file_name, [inputs[file_name]], output_dir)
    else:
      contents = []
      for data in file_content:
        contents.append(inputs[data])
      create_file(file_name, contents, output_dir)


def convert_localized_strings(formats):
  """Converts localized strings."""
  # Make a copy of formats to avoid modifying it
  formats = copy.deepcopy(formats)

  env_locales = os.getenv('LOCALES')
  if env_locales:
    locales = env_locales.split()
  else:
    locales = formats[KEY_LOCALES]

  styles = formats[KEY_STYLES]
  fonts = formats[KEY_FONTS]
  default_font = fonts.get(DEFAULT_NAME)

  # Sources are one .grd file with identifiers chosen by engineers and
  # corresponding English texts, as well as a set of .xlt files (one for each
  # language other than US english) with a mapping from hash to translation.
  # Because the keys in the xlt files are a hash of the English source text,
  # rather than our identifiers, such as "btn_cancel", we use the "grit"
  # command line tool to process the .grd and .xlt files, producing a set of
  # .json files mapping our identifier to the translated string, one for every
  # language including US English.

  # Create a temporary directory to place the translation output from grit in.
  json_dir = tempfile.mkdtemp()

  # This invokes the grit build command to generate JSON files from the XTB
  # files containing translations.  The results are placed in `json_dir` as
  # specified in firmware_strings.grd, i.e. one JSON file per locale.
  subprocess.check_call([
      'grit',
      '-i', os.path.join(LOCALE_DIR, STRINGS_GRD_FILE),
      'build',
      '-o', os.path.join(json_dir)
  ])

  # Ignore SIGINT in child processes
  sigint_handler = signal.signal(signal.SIGINT, signal.SIG_IGN)
  pool = multiprocessing.Pool(multiprocessing.cpu_count())
  signal.signal(signal.SIGINT, sigint_handler)

  results = []
  for locale in locales:
    print(locale, end=' ', flush=True)
    inputs = parse_locale_input_files(locale, json_dir)
    output_dir = os.path.normpath(os.path.join(STAGE_DIR, 'locale', locale))
    if not os.path.exists(output_dir):
      os.makedirs(output_dir)
    files = formats[KEY_FILES]

    # Now parse strings for optional features
    if os.getenv('DIAGNOSTIC_UI') == '1' and DIAGNOSTIC_FILES in formats:
      files.update(formats[DIAGNOSTIC_FILES])

    build_text_files(inputs, files, output_dir)

    results += [pool.apply_async(convert_text_to_png,
                                 (locale,
                                  os.path.join(output_dir, '%s.txt' % name),
                                  fonts.get(locale, default_font),
                                  '0',
                                  output_dir,
                                  [styles.get(name)]))
                for name in formats[KEY_FILES]]
  pool.close()
  if json_dir is not None:
    shutil.rmtree(json_dir)
  print()

  try:
    success = [r.get() for r in results]
  except KeyboardInterrupt:
    pool.terminate()
    pool.join()
    exit('Aborted by user')
  else:
    pool.join()
    if not all(success):
      exit('Failed to render some locales')


def build_strings():
  """Builds text strings."""
  with open(FORMAT_FILE, encoding='utf-8') as f:
    formats = yaml.load(f)

  # Convert glyphs
  print('Converting glyphs...')
  convert_glyphs()

  # Convert generic (locale-independent) strings
  styles = formats[KEY_STYLES]
  fonts = formats[KEY_FONTS]
  default_font = fonts.get(DEFAULT_NAME)

  for input_file in glob.glob(os.path.join(STRINGS_DIR, '*.txt')):
    name, _ = os.path.splitext(os.path.basename(input_file))
    style = styles.get(name)
    if not convert_text_to_png(None, input_file, default_font, '0',
                               STAGE_DIR, options=[style]):
      exit('Failed to convert text %s' % input_file)

  # Convert localized strings
  convert_localized_strings(formats)


def load_boards_config(filename):
  """Loads the configuration of all boards from `filename`.

  Args:
    filename: File name of a YAML config file.

  Returns:
    A dictionary mapping each board name to its config.
  """
  with open(filename, 'rb') as file:
    raw = yaml.load(file)

  configs = {}
  default = raw[DEFAULT_NAME]
  if not default:
    raise BuildImageError('Default configuration is not found')
  for boards, params in raw.items():
    if boards == DEFAULT_NAME:
      continue
    config = copy.deepcopy(default)
    if params:
      config.update(params)
    for board in boards.replace(',', ' ').split():
      configs[board] = config

  return configs


class Converter(object):
  """Converter from assets, texts, URLs, and fonts to bitmap images.

  Attributes:
    ASSET_DIR (str): Directory of image assets.
    DEFAULT_OUTPUT_EXT (str): Default output file extension.
    DEFAULT_REPLACE_MAP (dict): Default mapping of file replacement. For
      {'a': 'b'}, "a.*" will be converted to "b.*".
    SCALE_BASE (int): See ASSET_SCALES below.
    DEFAULT_FONT_SCALE (tuple): Scale (width and height) of the font images.
    ASSET_SCALES (dict): Scale of each image asset. Key is the image name and
      value is a tuple (w, h), which are the width and height relative to the
      screen resolution. For example, if SCALE_BASE is 1000, (500, 100) means
      the image will be scaled to 50% of the screen width and 10% of the screen
      height.
    TEXT_SCALES (dict): Scale of each localized text image. The meaning is
      similar to ASSET_SCALES.
    ASSET_MAX_COLORS (int): Maximum colors to use for converting image assets
      to bitmaps.
    DEFAULT_BACKGROUND (tuple): Default background color.
    BACKGROUND_COLORS (dict): Background color of each image. Key is the image
      name and value is a tuple of RGB values.
  """

  ASSET_DIR = 'assets'
  DEFAULT_OUTPUT_EXT = '.bmp'

  DEFAULT_REPLACE_MAP = {
      'rec_sel_desc1_no_sd': '',
      'rec_sel_desc1_no_phone_no_sd': '',
      'rec_disk_step1_desc0_no_sd': '',
      'rec_to_dev_desc1_phyrec': '',
      'rec_to_dev_desc1_power': '',
      'navigate0_tablet': '',
      'navigate1_tablet': '',
      'nav-button_power': '',
      'nav-button_volume_up': '',
      'nav-button_volume_down': '',
      'broken_desc_phyrec': '',
      'broken_desc_detach': '',
  }

  # scales
  SCALE_BASE = 1000     # 100.0%

  # These are supposed to be kept in sync with the numbers set in depthcharge
  # to avoid runtime scaling, which makes images blurry.
  DEFAULT_ASSET_SCALE = (0, 30)
  DEFAULT_TEXT_SCALE = (0, 24)
  DEFAULT_FONT_SCALE = (0, 20)
  LANG_SCALE = (0, 26)
  ICON_SCALE = (0, 45)
  STEP_ICON_SCALE = (0, 28)
  TITLE_SCALE = (0, 42)
  BUTTON_SCALE = (0, 20)
  BUTTON_ICON_SCALE = (0, 24)
  BUTTON_ARROW_SCALE = (0, 20)
  QR_FOOTER_SCALE = (0, 108)
  QR_DESC_SCALE = (0, 228)
  FOOTER_TEXT_SCALE = (0, 20)

  ASSET_SCALES = {
      'separator': None,
      'ic_globe': (0, 20),
      'ic_dropdown': (0, 24),
      'ic_info': ICON_SCALE,
      'ic_warning': ICON_SCALE,
      'ic_error': ICON_SCALE,
      'ic_dev_mode': ICON_SCALE,
      'ic_restart': ICON_SCALE,
      'ic_1': STEP_ICON_SCALE,
      'ic_1-done': STEP_ICON_SCALE,
      'ic_2': STEP_ICON_SCALE,
      'ic_2-done': STEP_ICON_SCALE,
      'ic_3': STEP_ICON_SCALE,
      'ic_3-done': STEP_ICON_SCALE,
      'ic_done': STEP_ICON_SCALE,
      'ic_search': BUTTON_ICON_SCALE,
      'ic_search_focus': BUTTON_ICON_SCALE,
      'ic_settings': BUTTON_ICON_SCALE,
      'ic_settings_focus': BUTTON_ICON_SCALE,
      'ic_power': BUTTON_ICON_SCALE,
      'ic_power_focus': BUTTON_ICON_SCALE,
      'ic_dropleft': BUTTON_ARROW_SCALE,
      'ic_dropleft_focus': BUTTON_ARROW_SCALE,
      'ic_dropright': BUTTON_ARROW_SCALE,
      'ic_dropright_focus': BUTTON_ARROW_SCALE,
      'qr_rec': QR_FOOTER_SCALE,
      'qr_rec_phone': QR_DESC_SCALE,
  }

  TEXT_SCALES = {
      'language': LANG_SCALE,
      'firmware_sync_title': TITLE_SCALE,
      'broken_title': TITLE_SCALE,
      'adv_options_title': TITLE_SCALE,
      'debug_info_title': TITLE_SCALE,
      'firmware_log_title': TITLE_SCALE,
      'rec_sel_title': TITLE_SCALE,
      'rec_step1_title': TITLE_SCALE,
      'rec_phone_step2_title': TITLE_SCALE,
      'rec_disk_step2_title': TITLE_SCALE,
      'rec_disk_step3_title': TITLE_SCALE,
      'rec_invalid_title': TITLE_SCALE,
      'rec_to_dev_title': TITLE_SCALE,
      'dev_title': TITLE_SCALE,
      'dev_to_norm_title': TITLE_SCALE,
      'dev_boot_ext_title': TITLE_SCALE,
      'dev_invalid_disk_title': TITLE_SCALE,
      'dev_select_bootloader_title': TITLE_SCALE,
      'diag_menu_title': TITLE_SCALE,
      'diag_storage_title': TITLE_SCALE,
      'diag_memory_quick_title': TITLE_SCALE,
      'diag_memory_full_title': TITLE_SCALE,
      'btn_dev_mode': BUTTON_SCALE,
      'btn_debug_info': BUTTON_SCALE,
      'btn_firmware_log': BUTTON_SCALE,
      'btn_page_up': BUTTON_SCALE,
      'btn_page_down': BUTTON_SCALE,
      'btn_rec_by_phone': BUTTON_SCALE,
      'btn_rec_by_disk': BUTTON_SCALE,
      'btn_adv_options': BUTTON_SCALE,
      'btn_secure_mode': BUTTON_SCALE,
      'btn_int_disk': BUTTON_SCALE,
      'btn_ext_disk': BUTTON_SCALE,
      'btn_alt_bootloader': BUTTON_SCALE,
      'btn_launch_diag': BUTTON_SCALE,
      'btn_diag_storage': BUTTON_SCALE,
      'btn_diag_memory_quick': BUTTON_SCALE,
      'btn_diag_memory_full': BUTTON_SCALE,
      'btn_diag_cancel': BUTTON_SCALE,
      'btn_next': BUTTON_SCALE,
      'btn_back': BUTTON_SCALE,
      'btn_confirm': BUTTON_SCALE,
      'btn_cancel': BUTTON_SCALE,
      'model': FOOTER_TEXT_SCALE,
      'help_center': FOOTER_TEXT_SCALE,
      'rec_url': FOOTER_TEXT_SCALE,
      'navigate0': FOOTER_TEXT_SCALE,
      'navigate1': FOOTER_TEXT_SCALE,
      'navigate0_tablet': FOOTER_TEXT_SCALE,
      'navigate1_tablet': FOOTER_TEXT_SCALE,
  }

  # background colors
  DEFAULT_BACKGROUND = (0x20, 0x21, 0x24)
  LANG_HEADER_BACKGROUND = (0x16, 0x17, 0x19)
  LINK_SELECTED_BACKGROUND = (0x2a, 0x2f, 0x39)
  ASSET_MAX_COLORS = 128

  BACKGROUND_COLORS = {
      'ic_dropdown': LANG_HEADER_BACKGROUND,
      'ic_dropleft_focus': LINK_SELECTED_BACKGROUND,
      'ic_dropright_focus': LINK_SELECTED_BACKGROUND,
      'ic_globe': LANG_HEADER_BACKGROUND,
      'ic_search_focus': LINK_SELECTED_BACKGROUND,
      'ic_settings_focus': LINK_SELECTED_BACKGROUND,
      'ic_power_focus': LINK_SELECTED_BACKGROUND,
  }

  def __init__(self, board, config, output):
    """Inits converter.

    Args:
      board: Board name.
      config: A dictionary of configuration parameters.
      output: Output directory.
    """
    self.board = board
    self.config = config
    self.set_dirs(output)
    self.set_screen()
    self.set_replace_map()
    self.set_locales()
    self.text_max_colors = self.config[TEXT_COLORS_KEY]

  def set_dirs(self, output):
    """Sets board output directory and stage directory.

    Args:
      output: Output directory.
    """
    self.output_dir = os.path.join(output, self.board)
    self.output_ro_dir = os.path.join(self.output_dir, 'locale', 'ro')
    self.output_rw_dir = os.path.join(self.output_dir, 'locale', 'rw')
    self.stage_dir = os.path.join(output, '.stage')
    self.temp_dir = os.path.join(self.stage_dir, 'tmp')

  def set_screen(self):
    """Sets screen width and height."""
    self.screen_width, self.screen_height = self.config[SCREEN_KEY]

    self.stretch = (1, 1)
    if self.config[PANEL_KEY]:
      # Calculate 'stretch'. It's used to shrink images horizontally so that
      # resulting images will look proportional to the original image on the
      # stretched display. If the display is not stretched, meaning aspect
      # ratio is same as the screen where images were rendered (1366x766),
      # no shrinking is performed.
      panel_width, panel_height = self.config[PANEL_KEY]
      self.stretch = (self.screen_width * panel_height,
                      self.screen_height * panel_width)

    if self.stretch[0] > self.stretch[1]:
      raise BuildImageError('Panel aspect ratio (%f) is smaller than screen '
                            'aspect ratio (%f). It indicates screen will be '
                            'shrunk horizontally. It is currently unsupported.'
                            % (panel_width / panel_height,
                               self.screen_width / self.screen_height))

    # Set up square drawing area
    self.canvas_px = min(self.screen_width, self.screen_height)

  def set_replace_map(self):
    """Sets a map replacing images.

    For each (key, value), image 'key' will be replaced by image 'value'.
    """
    replace_map = self.DEFAULT_REPLACE_MAP.copy()

    if os.getenv('DETACHABLE') == '1':
      replace_map.update({
          'nav-key_enter': 'nav-button_power',
          'nav-key_up': 'nav-button_volume_up',
          'nav-key_down': 'nav-button_volume_down',
          'navigate0': 'navigate0_tablet',
          'navigate1': 'navigate1_tablet',
          'broken_desc': 'broken_desc_detach',
      })

    physical_presence = os.getenv('PHYSICAL_PRESENCE')
    if physical_presence == 'recovery':
      replace_map['rec_to_dev_desc1'] = 'rec_to_dev_desc1_phyrec'
      replace_map['broken_desc'] = 'broken_desc_phyrec'
    elif physical_presence == 'power':
      replace_map['rec_to_dev_desc1'] = 'rec_to_dev_desc1_power'
    elif physical_presence != 'keyboard':
      raise BuildImageError('Invalid physical presence setting %s for board %s'
                            % (physical_presence, self.board))

    if not self.config[SDCARD_KEY]:
      replace_map.update({
          'rec_sel_desc1': 'rec_sel_desc1_no_sd',
          'rec_sel_desc1_no_phone': 'rec_sel_desc1_no_phone_no_sd',
          'rec_disk_step1_desc0': 'rec_disk_step1_desc0_no_sd',
      })

    self.replace_map = replace_map

  def set_locales(self):
    """Sets a list of locales for which localized images are converted."""
    # LOCALES environment variable can overwrite boards.yaml
    env_locales = os.getenv('LOCALES')
    rtl_locales = set(self.config[RTL_KEY])
    hi_res_locales = set(self.config[HI_RES_KEY])
    if env_locales:
      locales = env_locales.split()
    else:
      locales = self.config[LOCALES_KEY]
      # Check rtl_locales are contained in locales.
      unknown_rtl_locales = rtl_locales - set(locales)
      if unknown_rtl_locales:
        raise BuildImageError('Unknown locales %s in %s' %
                              (list(unknown_rtl_locales), RTL_KEY))
      # Check hi_res_locales are contained in locales.
      unknown_hi_res_locales = hi_res_locales - set(locales)
      if unknown_hi_res_locales:
        raise BuildImageError('Unknown locales %s in %s' %
                              (list(unknown_hi_res_locales), HI_RES_KEY))
    self.locales = [LocaleInfo(code, code in rtl_locales,
                               code in hi_res_locales)
                    for code in locales]

  def calculate_dimension(self, original, scale, num_lines):
    """Calculates scaled width and height.

    This imitates the function of Depthcharge with the same name.

    Args:
      original: (width, height) of the original image.
      scale: (x, y) scale parameter relative to the canvas size using
        SCALE_BASE as a base.
      num_lines: multiplication factor for the y-dimension.

    Returns:
      (width, height) of the scaled image.
    """
    dim_width, dim_height = (0, 0)
    scale_x, scale_y = scale
    org_width, org_height = original

    if scale_x == 0 and scale_y == 0:
      raise BuildImageError('Invalid scale parameter: %s' % (scale))
    if scale_x > 0:
      dim_width = int(self.canvas_px * scale_x / self.SCALE_BASE)
    if scale_y > 0:
      dim_height = int(self.canvas_px * scale_y / self.SCALE_BASE) * num_lines
    if scale_x == 0:
      dim_width = org_width * dim_height // org_height
    if scale_y == 0:
      dim_height = org_height * dim_width // org_width

    dim_width = int(dim_width * self.stretch[0] / self.stretch[1])

    return dim_width, dim_height

  def _get_svg_height(self, svg_file):
    tree = ElementTree.parse(svg_file)
    height = tree.getroot().attrib['height']
    m = re.match('([0-9]+)pt', height)
    if not m:
      raise BuildImageError('Cannot get height from %s' % svg_file)
    return int(m.group(1))

  def get_num_lines(self, file, one_line_dir):
    """Gets the number of lines of text in `file`."""
    name, _ = os.path.splitext(os.path.basename(file))
    svg_name = name + '.svg'
    multi_line_file = os.path.join(os.path.dirname(file), svg_name)
    one_line_file = os.path.join(one_line_dir, svg_name)
    # The number of lines id determined by comparing the height of
    # `multi_line_file` with `one_line_file`, where the latter is generated
    # without the '--width' option passed to pango-view.
    height = self._get_svg_height(multi_line_file)
    line_height = self._get_svg_height(one_line_file)
    return int(round(height / line_height))

  def convert_svg_to_png(self, svg_file, png_file, scale, num_lines,
                         background):
    """Converts .svg file to .png file."""
    background_hex = ''.join(format(x, '02x') for x in background)
    # If the width/height of the SVG file is specified in points, the
    # rsvg-convert command with default 90DPI will potentially cause the pixels
    # at the right/bottom border of the output image to be transparent (or
    # filled with the specified background color).  This seems like an
    # rsvg-convert issue regarding image scaling.  Therefore, use 72DPI here
    # to avoid the scaling.
    command = ['rsvg-convert',
               '--background-color', "'#%s'" % background_hex,
               '--dpi-x', '72',
               '--dpi-y', '72',
               '-o', png_file]
    if scale:
      width = int(self.canvas_px * scale[0] / self.SCALE_BASE)
      height = int(self.canvas_px * scale[1] / self.SCALE_BASE) * num_lines
      if width:
        command.extend(['--width', '%d' % width])
      if height:
        command.extend(['--height', '%d' % height])
    command.append(svg_file)
    subprocess.check_call(' '.join(command), shell=True)

  def convert_to_bitmap(self, input_file, scale, num_lines, background, output,
                        max_colors):
    """Converts an image file `input_file` to a BMP file `output`."""
    image = Image.open(input_file)

    # Process alpha channel and transparency.
    if image.mode == 'RGBA':
      target = Image.new('RGB', image.size, background)
      image.load()  # required for image.split()
      mask = image.split()[-1]
      target.paste(image, mask=mask)
    elif (image.mode == 'P') and ('transparency' in image.info):
      exit('Sorry, PNG with RGBA palette is not supported.')
    elif image.mode != 'RGB':
      target = image.convert('RGB')
    else:
      target = image

    # Process scaling
    if scale:
      new_size = self.calculate_dimension(image.size, scale, num_lines)
      if new_size[0] == 0 or new_size[1] == 0:
        print('Scaling', input_file)
        print('Warning: width or height is 0 after resizing: '
              'scale=%s size=%s stretch=%s new_size=%s' %
              (scale, image.size, self.stretch, new_size))
        return
      target = target.resize(new_size, Image.BICUBIC)

    # Export and downsample color space.
    target.convert('P', dither=None, colors=max_colors, palette=Image.ADAPTIVE
                   ).save(output)

    with open(output, 'rb+') as f:
      f.seek(BMP_HEADER_OFFSET_NUM_LINES)
      f.write(bytearray([num_lines]))

  def convert(self, files, output_dir, scales, max_colors, one_line_dir=None):
    """Converts file(s) to bitmap format."""
    if not files:
      raise BuildImageError('Unable to find file(s) to convert')

    for file in files:
      name, ext = os.path.splitext(os.path.basename(file))
      output = os.path.join(output_dir, name + self.DEFAULT_OUTPUT_EXT)

      background = self.BACKGROUND_COLORS.get(name, self.DEFAULT_BACKGROUND)
      scale = scales[name]

      if name in self.replace_map:
        name = self.replace_map[name]
        if not name:
          continue
        print('Replace: %s => %s' % (file, name))
        file = os.path.join(os.path.dirname(file), name + ext)

      # Determine num_lines in order to scale the image
      # TODO(b/159399377): Wrap lines for texts other than descriptions.
      if one_line_dir and ('_desc' in name or name.startswith('navigate')):
        num_lines = self.get_num_lines(file, one_line_dir)
      else:
        num_lines = 1

      if ext == '.svg':
        png_file = os.path.join(self.temp_dir, name + '.png')
        self.convert_svg_to_png(file, png_file, scale, num_lines, background)
        file = png_file

      self.convert_to_bitmap(
          file, scale, num_lines, background, output, max_colors)

  def convert_assets(self):
    """Converts images in assets folder."""
    files = []
    files.extend(glob.glob(os.path.join(self.ASSET_DIR, SVG_FILES)))
    files.extend(glob.glob(os.path.join(self.ASSET_DIR, PNG_FILES)))
    scales = defaultdict(lambda: self.DEFAULT_ASSET_SCALE)
    scales.update(self.ASSET_SCALES)
    self.convert(files, self.output_dir, scales, self.ASSET_MAX_COLORS)

  def convert_generic_strings(self):
    """Converts generic (locale-independent) strings."""
    scales = self.TEXT_SCALES.copy()
    files = glob.glob(os.path.join(self.stage_dir, SVG_FILES))
    self.convert(files, self.output_dir, scales, self.text_max_colors)

  def convert_localized_strings(self):
    """Converts localized strings."""
    # Using stderr to report progress synchronously
    print('  processing:', end='', file=sys.stderr, flush=True)
    for locale_info in self.locales:
      locale = locale_info.code
      ro_locale_dir = os.path.join(self.output_ro_dir, locale)
      stage_locale_dir = os.path.join(STAGE_LOCALE_DIR, locale)
      if locale_info.hi_res:
        scales = defaultdict(lambda: self.DEFAULT_TEXT_SCALE)
        scales.update(self.TEXT_SCALES)
        print(' ' + locale, end='', file=sys.stderr, flush=True)
      else:
        # We use low-res images for these locales and turn off scaling
        # to make the files fit in a ROM. Note that these text images will
        # be scaled by Depthcharge to be the same height as hi-res texts.
        scales = defaultdict(lambda: None)
        print(' ' + locale + '/lo', end='', file=sys.stderr, flush=True)
      os.makedirs(ro_locale_dir)
      self.convert(
          glob.glob(os.path.join(stage_locale_dir, SVG_FILES)),
          ro_locale_dir, scales, self.text_max_colors,
          one_line_dir=os.path.join(stage_locale_dir, ONE_LINE_DIR))
    print(file=sys.stderr)

  def move_language_images(self):
    """Renames language bitmaps and move to self.output_dir.

    The directory self.output_dir contains locale-independent images, and is
    used for creating vbgfx.bin by archive_images.py.
    """
    for locale_info in self.locales:
      locale = locale_info.code
      ro_locale_dir = os.path.join(self.output_ro_dir, locale)
      old_file = os.path.join(ro_locale_dir, 'language.bmp')
      new_file = os.path.join(self.output_dir, 'language_%s.bmp' % locale)
      if os.path.exists(new_file):
        raise BuildImageError('File already exists: %s' % new_file)
      shutil.move(old_file, new_file)

  def convert_fonts(self):
    """Converts font images"""
    scales = defaultdict(lambda: self.DEFAULT_FONT_SCALE)
    files = glob.glob(os.path.join(STAGE_FONT_DIR, SVG_FILES))
    font_output_dir = os.path.join(self.output_dir, 'font')
    os.makedirs(font_output_dir)
    self.convert(files, font_output_dir, scales, self.text_max_colors)

  def copy_images_to_rw(self):
    """Copies localized images specified in boards.yaml for RW override."""
    if not self.config[RW_OVERRIDE_KEY]:
      print('  No localized images are specified for RW, skipping')
      return

    for locale_info in self.locales:
      locale = locale_info.code
      rw_locale_dir = os.path.join(self.output_ro_dir, locale)
      ro_locale_dir = os.path.join(self.output_rw_dir, locale)
      os.makedirs(rw_locale_dir)

      for name in self.config[RW_OVERRIDE_KEY]:
        ro_src = os.path.join(ro_locale_dir, name + self.DEFAULT_OUTPUT_EXT)
        rw_dst = os.path.join(rw_locale_dir, name + self.DEFAULT_OUTPUT_EXT)
        shutil.copyfile(ro_src, rw_dst)

  def create_locale_list(self):
    """Creates locale list as a CSV file.

    Each line in the file is of format "code,rtl", where
    - "code": language code of the locale
    - "rtl": "1" for right-to-left language, "0" otherwise
    """
    with open(os.path.join(self.output_dir, 'locales'), 'w') as f:
      for locale_info in self.locales:
        f.write('{},{}\n'.format(locale_info.code,
                                 int(locale_info.rtl)))

  def build(self):
    """Builds all images required by a board."""
    # Clean up output directory
    if os.path.exists(self.output_dir):
      shutil.rmtree(self.output_dir)
    os.makedirs(self.output_dir)

    if not os.path.exists(self.stage_dir):
      raise BuildImageError('Missing stage folder. Run make in strings dir.')

    # Clean up temp directory
    if os.path.exists(self.temp_dir):
      shutil.rmtree(self.temp_dir)
    os.makedirs(self.temp_dir)

    print('Converting asset images...')
    self.convert_assets()

    print('Converting generic strings...')
    self.convert_generic_strings()

    print('Converting localized strings...')
    self.convert_localized_strings()

    print('Moving language images to locale-independent directory...')
    self.move_language_images()

    print('Creating locale list file...')
    self.create_locale_list()

    print('Converting fonts...')
    self.convert_fonts()

    print('Copying specified images to RW packing directory...')
    self.copy_images_to_rw()


def build_images(board):
  """Builds images for `board`."""
  configs = load_boards_config(BOARDS_CONFIG_FILE)
  print('Building for ' + board)
  converter = Converter(board, configs[board], OUTPUT_DIR)
  converter.build()


def main():
  """Builds bitmaps for firmware screens."""
  parser = argparse.ArgumentParser()
  parser.add_argument('board', help='Target board')
  args = parser.parse_args()
  build_strings()
  build_images(args.board)


if __name__ == '__main__':
  main()