Class: BbEPUB::Transform::CoverImage

Inherits:
Bookbinder::Transform
  • Object
show all
Defined in:
lib/bb-epub/transform/cover_image.rb

Overview

The best source of information about wading through the EPUB cover image quagmire has always been Keith’s article on the Threepress blog:

http://blog.safaribooksonline.com/2009/11/20/best-practices-in-epub-cover-images/

He added an update for EPUB3, which follows the spec but is a bit easier to grok:

http://blog.safaribooksonline.com/2011/05/26/covers-in-epub3/

Instance Method Summary collapse

Instance Method Details

#cover_item_from_component(package, cmpt) ⇒ Object

TODO: support SVG images too.



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# File 'lib/bb-epub/transform/cover_image.rb', line 100

def cover_item_from_component(package, cmpt)
  package.if_file(cmpt['path']) { |cmpt_file|
    return  unless cmpt_doc = cmpt_file.document('r')
    return  unless img_tag = cmpt_doc.find('body img')
    opf_doc = package.file(:opf).document('r')
    opf_doc.find('opf|manifest > opf|item[href="'+img_tag['src']+'"]')
  }
rescue
  nil
end

#cover_item_from_cover_page(package) ⇒ Object 



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# File 'lib/bb-epub/transform/cover_image.rb', line 89

def cover_item_from_cover_page(package)
  if (nav = package.map['nav']) && (landmarks = nav['landmarks'])
    if landmark = landmarks.detect { |it| it['type'] == 'cover' }
      return package.map['spine'].detect { |c| c['path'] == landmark['path'] }
    end
  end
end

#cover_item_from_manifest(package, opf_doc) ⇒ Object 



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# File 'lib/bb-epub/transform/cover_image.rb', line 73

def cover_item_from_manifest(package, opf_doc)
  opf_doc.find('opf|manifest > opf|item[properties~="cover-image"]') ||
    opf_doc.find('opf|manifest > opf|item[id="cover-image"]') ||
    opf_doc.find('opf|manifest > opf|item[id="cover_image"]')
end

#cover_item_from_metadata(package, opf_doc) ⇒ Object 



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# File 'lib/bb-epub/transform/cover_image.rb', line 80

def cover_item_from_metadata(package, opf_doc)
  cover_meta_props = (package.map['metadata'] || {}).delete('cover')
  if cover_meta_props && cover_meta_props.any?
    cover_image_id = cover_meta_props.first['content']['@']
    opf_doc.find('opf|manifest > opf|item[id="'+cover_image_id+'"]')
  end
end

#cover_resource_from_item(package, cover_item) ⇒ Object 



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# File 'lib/bb-epub/transform/cover_image.rb', line 112

def cover_resource_from_item(package, cover_item)
  return nil  unless cover_item && cover_item['id']
  if cmpt = package.map['spine'].detect { |c| c['id'] == cover_item['id'] }
    unless cover_item = cover_item_from_component(package, cmpt)
      package.warn("Did not discover cover image in #{cmpt['path']}. SVG?")
      return nil
    end
  end
  package.map['resources'].detect { |r| r['id'] == cover_item['id'] }
end

#dependencies ⇒ Object 



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# File 'lib/bb-epub/transform/cover_image.rb', line 14

def dependencies
  [
    BbEPUB::Transform::Metadata,
    BbEPUB::Transform::CoverPage
  ]
end

#from_map(package) ⇒ Object

Belt and braces: give the manifest item a property of ‘cover-image’, an ‘id’ of ‘cover-image’ (updating any idrefs) and create a meta tag with ‘name’=‘cover’ and ‘content’=‘cover-image’.



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# File 'lib/bb-epub/transform/cover_image.rb', line 50

def from_map(package)
  return  unless package.map['cover'] && cover = package.map['cover']['front']
  opf_doc = package.file(:opf).document

  opf_doc.new_node('item', :append => 'opf|manifest') { |manifest_item_tag|
    manifest_item_tag['href'] = package.make_href(cover['path'])
    manifest_item_tag['media-type'] = cover['media-type']
    manifest_item_tag['id'] = 'cover-image'
    manifest_item_tag['properties'] = 'cover-image'
  }

  cover_id = package.make_id(cover['path'])
  opf_doc.each('[idref="'+cover_id+'"]') { |idref|
    idref['idref'] = cover_id
  }

  opf_doc.new_node('meta', :append => 'opf|metadata') { |cover_meta_tag|
    cover_meta_tag['name'] = 'cover'
    cover_meta_tag['content'] = 'cover-image'
  }
end

#to_map(package) ⇒ Object

If it’s EPUB3, the cover will be in the ‘properties’ attribute of the manifest item: ‘cover-image’

Otherwise, look for a manifest item with an ‘id’ of ‘cover-image’.

Or, look for a meta tag with a ‘name’ of ‘cover’, then find the manifest item that has the ‘id’ that matches meta’s ‘content’.

Set map to this item (and remove it from map).



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# File 'lib/bb-epub/transform/cover_image.rb', line 32

def to_map(package)
  package.map['cover'] = {}
  opf_doc = package.file(:opf).document('r')
  cover_item = cover_item_from_manifest(package, opf_doc) ||
    cover_item_from_metadata(package, opf_doc) ||
    cover_item_from_cover_page(package)
  if cover_resource = cover_resource_from_item(package, cover_item)
    package.map['resources'].delete(cover_resource)
    package.map['cover'].update("front" => cover_resource)
  end
end