Class: Softcover::Builders::Epub

Inherits:
Softcover::Builder show all
Includes:
EpubUtils, Output
Defined in:
lib/softcover/builders/epub.rb

Constant Summary

Constants included from Utils

Utils::UNITS

Instance Attribute Summary

Attributes inherited from Softcover::Builder

#built_files, #manifest

Instance Method Summary collapse

Methods included from EpubUtils

#content_opf_template, #cover?, #cover_filename, #cover_img, #cover_img_path, #escape, #images_dir, #nav_filename, #nav_html_template, #toc_ncx_template, #xhtml

Methods included from Output

should_output?, silence!, silent?, #system, unsilence!

Methods inherited from Softcover::Builder

#clean!, #initialize

Methods included from Utils

#add_highlight_class!, #article?, #as_size, #book_file_lines, #chapter_label, #commands, #current_book, #dependency_filename, #digest, #executable, #execute, #filename_or_default, #first_path, #get_filename, #html_extension, #in_book_directory?, #language_labels, #linux?, #logged_in?, #master_content, #master_filename, #master_latex_header, #mkdir, #non_comment_lines, #os_x?, #path, #polytexnic_html, #raw_lines, #reset_current_book!, #rm, #rm_r, #silence, #silence_stream, #source, #template_dir, #tmpify, #unpublish_slug, #write_master_latex_file, #write_pygments_file

Constructor Details

This class inherits a constructor from Softcover::Builder

Instance Method Details

#build!(options = {}) ⇒ Object 



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# File 'lib/softcover/builders/epub.rb', line 145

def build!(options={})
  @preview = options[:preview]
  Softcover::Builders::Html.new.build!
  if manifest.markdown?
    opts = options.merge({ source: :polytex, origin: :markdown })
    self.manifest = Softcover::BookManifest.new(opts)
  end
  remove_html
  remove_images
  create_directories
  write_mimetype
  write_container_xml
  write_ibooks_xml
  copy_image_files
  write_html(options)
  write_contents(options)
  create_style_files(options)
  write_toc
  write_nav
  make_epub(options)
  move_epub
end

#chapter_name(n) ⇒ Object 



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# File 'lib/softcover/builders/epub.rb', line 598

def chapter_name(n)
  n == 0 ? language_labels["frontmatter"] : strip_html(chapters[n].menu_heading)
end

#chapter_template(title, content) ⇒ Object

Returns the HTML template for a chapter.



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# File 'lib/softcover/builders/epub.rb', line 642

def chapter_template(title, content)
  %(<?xml version="1.0" encoding="utf-8"?>
  <!DOCTYPE html>

  <html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <title>#{title}</title>
    <link rel="stylesheet" href="styles/pygments.css" type="text/css" />
    <link rel="stylesheet" href="styles/softcover.css" type="text/css" />
    <link rel="stylesheet" href="styles/epub.css" type="text/css" />
    <link rel="stylesheet" href="styles/custom.css" type="text/css"/>
    <link rel="stylesheet" href="styles/custom_epub.css" type="text/css"/>
    <link rel="stylesheet" type="application/vnd.adobe-page-template+xml" href="styles/page-template.xpgt" />
  </head>

  <body>
    #{content}
  </body>
  </html>)
end

#chapters ⇒ Object

Returns the chapters to write.



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# File 'lib/softcover/builders/epub.rb', line 221

def chapters
  preview? ? manifest.preview_chapters : manifest.chapters
end

#clean_book_id(filename) ⇒ Object

Removes the ‘#book’ CSS id. For some reason, EPUB books hate the #book ids in the stylesheet (i.e., such books fail to validate), so remove them.



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# File 'lib/softcover/builders/epub.rb', line 438

def clean_book_id(filename)
  File.read(filename).gsub(/#book /, '')
end

#container_xml ⇒ Object 



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# File 'lib/softcover/builders/epub.rb', line 508

def container_xml
%(<?xml version="1.0"?>
<container version="1.0" xmlns="urn:oasis:names:tc:opendocument:xmlns:container">
    <rootfiles>
  <rootfile full-path="OEBPS/content.opf" media-type="application/oebps-package+xml"/>
   </rootfiles>
</container>)
end

#content_opf(options = {}) ⇒ Object

Returns the content configuration file.



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# File 'lib/softcover/builders/epub.rb', line 527

def content_opf(options={})
  man_ch = chapters.map do |chapter|
             %(<item id="#{chapter.slug}" href="#{xhtml(chapter.fragment_name)}" media-type="application/xhtml+xml"/>)
           end
    toc_ch = chapters.map do |chapter|
               %(<itemref idref="#{chapter.slug}"/>)
             end
  image_files = Dir['epub/OEBPS/images/**/*'].select { |f| File.file?(f) }
  images = image_files.map do |image|
             ext = File.extname(image).sub('.', '')   # e.g., 'png'
             ext = 'jpeg' if ext == 'jpg'
             # Strip off the leading 'epub/OEBPS'.
             sep  = File::SEPARATOR
             href = image.split(sep)[2..-1].join(sep)
             # Define an id based on the filename.
             # Prefix with 'img-' in case the filname starts with an
             # invalid character such as a number.
             label = File.basename(image).gsub('.', '-')
             id = "img-#{label}"
             %(<item id="#{id}" href="#{href}" media-type="image/#{ext}"/>)
           end

  manifest.html_title
  content_opf_template(manifest.html_title, manifest.copyright,
                       manifest.author, manifest.uuid, cover_id(options),
                       toc_ch, man_ch, images)
end

#copy_image_files ⇒ Object

Copies the image files from the HTML version of the document.



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# File 'lib/softcover/builders/epub.rb', line 443

def copy_image_files
  # Copy over all images to guarantee the same directory structure.
  FileUtils.cp_r(File.join('html', 'images'),
                 File.join('epub', 'OEBPS'))
  # Parse the full HTML file with Nokogiri to get images actually used.
  html = File.read(manifest.full_html_file)
  html_image_filenames = Nokogiri::HTML(html).css('img').map do |node|
                           node.attributes['src'].value
                         end
  # Form the corresponding EPUB image paths.
  used_image_filenames = html_image_filenames.map do |filename|
                           "epub/OEBPS/#{filename}"
                         end.to_set
  # Delete unused images.
  Dir.glob("epub/OEBPS/images/**/*").each do |image|
    next if File.directory?(image)
    rm image unless used_image_filenames.include?(image)
  end
end

#cover_id(options) ⇒ Object 



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# File 'lib/softcover/builders/epub.rb', line 571

def cover_id(options)
  cover?(options) ? "img-#{cover_img.sub('.', '-')}" : nil
end

#cover_page ⇒ Object 



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# File 'lib/softcover/builders/epub.rb', line 555

def cover_page
%(<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
  <title>Cover</title>
</head>
<body>
  <div id="cover">
     <img width="573" height="800" src="images/#{cover_img}" alt="cover" />
  </div>
</body>
</html>
)
end

#create_directories ⇒ Object 



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# File 'lib/softcover/builders/epub.rb', line 185

def create_directories
  mkdir('epub')
  mkdir(path('epub/OEBPS'))
  mkdir(path('epub/OEBPS/styles'))
  mkdir(path('epub/META-INF'))
  mkdir(images_dir)
  mkdir('ebooks')
end

#create_style_files(options) ⇒ Object 



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# File 'lib/softcover/builders/epub.rb', line 417

def create_style_files(options)
  html_styles = File.join('html', 'stylesheets')
  epub_styles = File.join('epub', 'OEBPS', 'styles')

  FileUtils.cp(File.join(html_styles, 'pygments.css'), epub_styles)
  File.write(File.join(epub_styles, 'softcover.css'),
             clean_book_id(path("#{html_styles}/softcover.css")))

  # Copy over the EPUB-specific CSS.
  template_dir = Softcover::Utils.template_dir(options)
  epub_css     = File.join(template_dir, epub_styles, 'epub.css')
  FileUtils.cp(epub_css, epub_styles)

  # Copy over custom CSS.
  File.write(File.join(epub_styles, 'custom.css'),
             clean_book_id(path("#{html_styles}/custom.css")))
end

#html_with_math(chapter, images_dir, texmath_dir, pngs, options = {}) ⇒ Object

Returns HTML for HTML source that includes math. As a side-effect, html_with_math creates PNGs corresponding to any math in the given source. The technique involves using PhantomJS to hit the HTML source for each page containing math to create SVGs for every math element. Since ereader support for SVGs is spotty, they are then converted to PNGs using Inkscape. The filenames are SHAs of their contents, which arranges both for unique filenames and for automatic disk caching.



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# File 'lib/softcover/builders/epub.rb', line 283

def html_with_math(chapter, images_dir, texmath_dir, pngs, options={})
  content = File.read(File.join("html",
                                "#{chapter.slug}.#{html_extension}"))
  pagejs = "#{File.dirname(__FILE__)}/utils/page.js"
  url = "file://#{Dir.pwd}/html/#{chapter.slug}.#{html_extension}"
  cmd = "#{phantomjs} #{pagejs} #{url}"
  silence { silence_stream(STDERR) { system cmd } }
  # Sometimes in tests the phantomjs_source.html file is missing.
  # It shouldn't ever happen, but it does no harm to skip it.
  return nil unless File.exist?('phantomjs_source.html')
  raw_source = File.read('phantomjs_source.html')
  source = strip_attributes(Nokogiri::HTML(raw_source))
  rm 'phantomjs_source.html'
  # Remove the first body div, which is the hidden MathJax SVGs.
  if (mathjax_svgs = source.at_css('body div'))
    mathjax_svgs.remove
  else
    # There's not actually any math, so return nil.
    return nil
  end
  # Remove all the unneeded raw TeX displays.
  source.css('script').each(&:remove)
  # Remove all the MathJax preview spans.
  source.css('MathJax_Preview').each(&:remove)
  # Suck out all the SVGs
  svgs   = source.css('div#book svg')
  frames = source.css('span.MathJax_SVG')
  svgs.zip(frames).each do |svg, frame|
    # Save the SVG file.
    svg['viewBox'] = svg['viewbox']
    svg.remove_attribute('viewbox')
    # Workaround for bug in Inkscape 0.91 on MacOS X:
    # extract height/width from svg attributes and move them to style attr
    svg_height = svg['height']  # in ex
    svg_width = svg['width']    # in ex
    svg['style'] += ' height:'+svg_height+';' + ' width:'+svg_width+';'
    svg.remove_attribute('height')
    svg.remove_attribute('width')
    # /Workaround
    first_child = frame.children.first
    first_child.replace(svg) unless svg == first_child
    output = svg.to_xhtml
    svg_filename = File.join(texmath_dir, "#{digest(output)}.svg")
    svg_abspath = File.join("#{Dir.pwd}", svg_filename)
    File.write(svg_filename, output)
    # Convert to PNG named:
    png_filename = svg_filename.sub('.svg', '.png')
    png_abspath = svg_abspath.sub('.svg', '.png')
    pngs << png_filename
    #
    # Settings for texmath images in ePub / mobi
    ex2em_height_scaling = 0.51     # =1ex/1em for math png height
    ex2em_valign_scaling = 0.481482 # =1ex/1em for math png vertical-align
    ex2pt_scale_factor = 15         # =1ex/1pt scaling for SVG-->PNG conv.
    # These are used a three-step process below: Compute, Convert, Replace
    # STEP1: compute height and vertical-align in `em` units
    svg_height_in_ex = Float(svg_height.gsub('ex',''))
    # MathJax sets SVG height in `ex` units but we want `em` units for PNG
    png_height = (svg_height_in_ex * ex2em_height_scaling).to_s + 'em'
    # Extract vertical-align css proprty for inline math equations:
    if svg.parent.parent.attr('class') == "inline_math"
      vertical_align = svg['style'].scan(/vertical-align: (.*?);/).flatten.first
      if vertical_align
        valign_in_ex = Float(vertical_align.gsub('ex',''))
        png_valign = (valign_in_ex * ex2em_valign_scaling).to_s + 'em'
      else
        png_valign = "0em"
      end
    else # No vertical align for displayed math
      png_valign = nil
    end
    # STEP2: Generate PNG from each SVG (unless PNG exists already).
    unless File.exist?(png_filename)
      h = ex2pt_scale_factor * svg_height_in_ex       # = PNG height in pt
      unless options[:silent] || options[:quiet]
        puts "Creating #{png_filename}"
      end
      # generate png from the MathJax_SVG using inkscape
      cmd = "#{inkscape} -f #{svg_abspath} -e #{png_abspath} -h #{h}pt"
      if options[:silent]
        silence { silence_stream(STDERR) { system cmd } }
      else
        silence_stream(STDERR) { system cmd }
      end
    end
    rm svg_filename
    # STEP 3: Replace svg element with an equivalent png.
    png = Nokogiri::XML::Node.new('img', source)
    png['src']    = File.join('images', 'texmath', File.basename(png_filename))
    png['alt']    = png_filename.sub('.png', '')
    png['style']  = 'height:' + png_height + ';'
    if png_valign
      png['style'] += ' vertical-align:' + png_valign + ';'
    end
    svg.replace(png)
  end
  # Make references relative.
  source.css('a.hyperref').each do |ref_node|
    ref_node['href'] = ref_node['href'].sub('.html',
                                            xhtml('_fragment.html'))
  end
  source.at_css('div#book').children.to_xhtml
end

#ibooks_xml ⇒ Object 



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# File 'lib/softcover/builders/epub.rb', line 517

def ibooks_xml
%(<?xml version="1.0" encoding="UTF-8"?>
<display_options>
  <platform name="*">
    <option name="specified-fonts">true</option>
  </platform>
</display_options>)
end

#inkscape ⇒ Object

Returns the Inkscape executable (if available).



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# File 'lib/softcover/builders/epub.rb', line 393

def inkscape
  @inkscape ||= executable(dependency_filename(:inkscape))
end

#make_epub(options = {}) ⇒ Object

Make the EPUB, which is basically just a zipped HTML file.



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# File 'lib/softcover/builders/epub.rb', line 464

def make_epub(options={})
  filename = manifest.filename
  zfname = filename + '.zip'
  base_file = "#{zip} -X0 #{zfname} mimetype"
  fullzip = "#{zip} -rDXg9"
  meta_info = "#{fullzip} #{zfname} META-INF -x \*.DS_Store -x mimetype"
  main_info = "#{fullzip} #{zfname} OEBPS    -x \*.DS_Store \*.gitkeep"
  rename = "mv #{zfname} #{filename}.epub"
  commands = [base_file, meta_info, main_info, rename]
  command = commands.join(' && ')
  Dir.chdir('epub') do
    if Softcover.test? || options[:quiet] || options[:silent]
      silence { system(command) }
    else
      system(command)
    end
  end
end

#math?(string) ⇒ Boolean

Returns true if a string appears to have LaTeX math. We detect math via opening math commands: (, [, and beginequation This gives a false positive when math is included in verbatim environments and nowhere else, but it does little harm (requiring only an unnecessary call to page.js).

Returns:

  • (Boolean) 


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# File 'lib/softcover/builders/epub.rb', line 413

def math?(string)
  !!string.match(/(?:\\\(|\\\[|\\begin{equation})/)
end

#move_epub ⇒ Object

Move the completed EPUB book to the ‘ebooks` directory. Note that we handle the case of a preview book as well.



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# File 'lib/softcover/builders/epub.rb', line 489

def move_epub
  origin = manifest.filename
  target = preview? ? origin + '-preview' : origin
  FileUtils.mv(File.join('epub',   "#{origin}.epub"),
               File.join('ebooks', "#{target}.epub"))
end

#nav_html ⇒ Object

Returns the nav HTML content.



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# File 'lib/softcover/builders/epub.rb', line 608

def nav_html
  if article?
    article = chapters.first
    nav_list = section_names_and_ids(article).map do |name, id|
                 %(<li> <a href="#{xhtml(article.fragment_name)}##{id}">#{name}</a></li>)
               end
  else
    nav_list = manifest.chapters.map do |chapter|
                 element = preview? ? chapter.title : nav_link(chapter)
                 %(<li>#{element}</li>)
               end
  end
  nav_html_template(manifest.html_title, nav_list)
end

#nav_link(chapter) ⇒ Object

Returns a navigation link for the chapter.



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# File 'lib/softcover/builders/epub.rb', line 624

def nav_link(chapter)
  %(<a href="#{xhtml(chapter.fragment_name)}">#{chapter.html_title}</a>)
end

#phantomjs ⇒ Object

Returns the PhantomJS executable (if available).



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# File 'lib/softcover/builders/epub.rb', line 388

def phantomjs
  @phantomjs ||= executable(dependency_filename(:phantomjs))
end

#preview? ⇒ Boolean

Returns true if generating a book preview.

Returns:

  • (Boolean) 


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# File 'lib/softcover/builders/epub.rb', line 169

def preview?
  !!@preview
end

#remove_html ⇒ Object

Removes HTML. All the HTML is generated, so this clears out any unused files.



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# File 'lib/softcover/builders/epub.rb', line 175

def remove_html
  FileUtils.rm(Dir.glob(path('epub/OEBPS/*.html')))
  FileUtils.rm(Dir.glob(path('epub/OEBPS/*.xhtml')))
end

#remove_images ⇒ Object

Removes images in case they are stale.



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# File 'lib/softcover/builders/epub.rb', line 181

def remove_images
  rm_r images_dir
end

#section_names_and_ids(article) ⇒ Object

Returns a list of the section names and CSS ids. Form is [[‘Beginning’, ‘sec-beginning’], [‘Next’, ‘sec-next’]]



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# File 'lib/softcover/builders/epub.rb', line 630

def section_names_and_ids(article)
  # Grab section names and ids from the article.
  filename = File.join('epub', 'OEBPS', xhtml(article.fragment_name))
  doc = Nokogiri::HTML(File.read(filename))
  names = doc.css('div.section>h2').map do |s|
            s.children.children.last.content
          end
  ids = doc.css('div.section').map { |s| s.attributes['id'].value }
  names.zip(ids)
end

#strip_attributes(doc) ⇒ Object

Strip attributes that are invalid in EPUB documents.



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# File 'lib/softcover/builders/epub.rb', line 398

def strip_attributes(doc)
  attrs = %w[data-tralics-id data-label data-number data-chapter
             role aria-readonly target]
  doc.tap do
    attrs.each do |attr|
      doc.xpath("//@#{attr}").remove
    end
  end
end

#strip_html(text) ⇒ Object

Strip HTML elements from the given text.



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# File 'lib/softcover/builders/epub.rb', line 603

def strip_html(text)
  Nokogiri::HTML.fragment(text).content
end

#toc_ncx ⇒ Object

Returns the Table of Contents for the spine.



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# File 'lib/softcover/builders/epub.rb', line 576

def toc_ncx
  chapter_nav = []

  if article?
    article = chapters.first
    section_names_and_ids(article).each_with_index do |(name, id), n|
      chapter_nav << %(<navPoint id="#{id}" playOrder="#{n+1}">)
      chapter_nav << %(    <navLabel><text>#{escape(name)}</text></navLabel>)
      chapter_nav << %(    <content src="#{xhtml(article.fragment_name)}##{id}"/>)
      chapter_nav << %(</navPoint>)
    end
  else
    chapters.each_with_index do |chapter, n|
      chapter_nav << %(<navPoint id="#{chapter.slug}" playOrder="#{n+1}">)
      chapter_nav << %(    <navLabel><text>#{chapter_name(n)}</text></navLabel>)
      chapter_nav << %(    <content src="#{xhtml(chapter.fragment_name)}"/>)
      chapter_nav << %(</navPoint>)
    end
  end
  toc_ncx_template(manifest.html_title, manifest.uuid, chapter_nav)
end

#write_container_xml ⇒ Object

Writes the container XML file. This is required by the EPUB standard.



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# File 'lib/softcover/builders/epub.rb', line 202

def write_container_xml
  File.write(path('epub/META-INF/container.xml'), container_xml)
end

#write_contents(options = {}) ⇒ Object

Writes the content.opf file. This is required by the EPUB standard.



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# File 'lib/softcover/builders/epub.rb', line 216

def write_contents(options={})
  File.write(path('epub/OEBPS/content.opf'), content_opf(options))
end

#write_html(options = {}) ⇒ Object

Writes the HTML for the EPUB. Included is a math detector that processes the page with MathJax (via page.js) so that math can be included in EPUB (and thence MOBI).



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# File 'lib/softcover/builders/epub.rb', line 228

def write_html(options={})
  texmath_dir = File.join(images_dir, 'texmath')
  mkdir images_dir
  mkdir texmath_dir

  File.write(path("epub/OEBPS/#{cover_filename}"), cover_page) if cover?(options)

  pngs = []
  chapters.each_with_index do |chapter, i|
    target_filename = path("epub/OEBPS/#{xhtml(chapter.fragment_name)}")
    File.open(target_filename, 'w') do |f|
      content = File.read(path("html/#{chapter.fragment_name}"))
      doc = strip_attributes(Nokogiri::HTML(content))
      # Use xhtml in references.
      doc.css('a.hyperref').each do |ref_node|
        ref_node['href'] = ref_node['href'].sub('.html', xhtml('.html'))
      end
      body = doc.at_css('body')
      if body.nil?
        $stderr.puts "\nError: Document not built due to empty chapter"
        $stderr.puts "Chapters must include a title using the Markdown"
        $stderr.puts "    # This is a chapter"
        $stderr.puts "or the LaTeX"
        $stderr.puts "    \\chapter{This is a chapter}"
        exit(1)
      end
      inner_html = body.children.to_xhtml
      if math?(inner_html)
        html = html_with_math(chapter, images_dir, texmath_dir, pngs,
                              options)
        html ||= inner_html # handle case of spurious math detection
      else
        html = inner_html
      end
      f.write(chapter_template("Chapter #{i}", html))
    end
  end
  # Clean up unused PNGs.
  png_files = Dir[path("#{texmath_dir}/*.png")]
  (png_files - pngs).each do |f|
    if File.exist?(f)
      puts "Removing unused PNG #{f}" unless options[:silent]
      FileUtils.rm(f)
    end
  end
end

#write_ibooks_xml ⇒ Object

Writes iBooks-specific XML. This allows proper display of monospace fonts in code samples, among other things.



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# File 'lib/softcover/builders/epub.rb', line 209

def write_ibooks_xml
  xml_filename = 'com.apple.ibooks.display-options.xml'
  File.write(path("epub/META-INF/#{xml_filename}"), ibooks_xml)
end

#write_mimetype ⇒ Object

Writes the mimetype file. This is required by the EPUB standard.



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# File 'lib/softcover/builders/epub.rb', line 196

def write_mimetype
  File.write(path('epub/mimetype'), 'application/epub+zip')
end

#write_nav ⇒ Object

Writes the navigation file. This is required by the EPUB standard.



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# File 'lib/softcover/builders/epub.rb', line 504

def write_nav
  File.write("epub/OEBPS/#{nav_filename}", nav_html)
end

#write_toc ⇒ Object

Writes the Table of Contents. This is required by the EPUB standard.



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# File 'lib/softcover/builders/epub.rb', line 498

def write_toc
  File.write('epub/OEBPS/toc.ncx', toc_ncx)
end

#zip ⇒ Object 



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# File 'lib/softcover/builders/epub.rb', line 483

def zip
  @zip ||= executable(dependency_filename(:zip))
end