root/trunk/lib/image_builder.rb

require 'tempfile'
begin
  # this works on the deb box
  require 'RMagick'
rescue LoadError
  begin
    # this works on my Mac
    require 'rmagick'
  rescue LoadError
    puts "ImageMagick not found. Using dummy."
    # Create a dummy magick module
    module Magick
      CenterGravity = OverCompositeOp = MaxRGB = NorthGravity = SouthGravity = nil
      class << self
      end
      class ZenaDummy
        def initialize(*a)
        end
        def method_missing(meth, *args)
          # do nothing
        end
      end
      class Image < ZenaDummy
      end
      class ImageList < ZenaDummy
      end
    end
  end
end

class ImageBuilder
  DEFAULT_FORMATS = {
    'tiny' =>   { :name=>'tiny', :size=>:force, :width=>16,  :height=>16 , :gravity=>Magick::CenterGravity   }.freeze,
    'mini' =>   { :name=>'mini', :size=>:force, :width=>32,  :height=>32 , :gravity=>Magick::CenterGravity   }.freeze,
    'square' => { :name=>'square', :size=>:limit, :width=>180, :height=>180, :gravity=>Magick::CenterGravity   }.freeze,
    'med'  =>   { :name=>'med',  :size=>:limit, :width=>280, :height=>186, :gravity=>Magick::CenterGravity   }.freeze,
    'top'  =>   { :name=>'top',  :size=>:force, :width=>280, :height=>186, :gravity => Magick::NorthGravity  }.freeze,
    'low'  =>   { :name=>'low',  :size=>:force, :width=>280, :height=>186, :gravity => Magick::SouthGravity  }.freeze,
    'side' =>   { :name=>'side', :size=>:force, :width=>220, :height=>500, :gravity=>Magick::CenterGravity   }.freeze,
    'std'  =>   { :name=>'std',  :size=>:limit, :width=>600, :height=>400, :gravity=>Magick::CenterGravity   }.freeze,
    'pv'   =>   { :name=>'pv',   :size=>:force, :width=>70,  :height=>70 , :gravity=>Magick::CenterGravity   }.freeze,
    'edit' =>   { :name=>'edit', :size=>:limit, :width=>400, :height=>400, :gravity=>Magick::CenterGravity   }.freeze,
    'full' =>   { :name=>'full', :size=>:keep                            , :gravity=>Magick::CenterGravity   }.freeze,
    nil    =>   { :name=>'full', :size=>:keep                            , :gravity=>Magick::CenterGravity   }.freeze,
  }.freeze

  # 'sepia'=>   { :size=>:limit, :width=>280, :ratio=>2/3.0, :post=>Proc.new {|img| img.sepiatone(Magick::MaxRGB * 0.8)}},
  
  class << self
    def image_content_type?(content_type)
      content_type =~ /image/
    end
    def dummy?
      Magick.const_defined?(:ZenaDummy)
    end
  end

  def initialize(h)
    params = {:height=>nil, :width=>nil, :path=>nil, :file=>nil, :actions=>[]}.merge(h)
    
    params.each do |k,v|
      case k
      when :height
        @height = v if v
      when :width
        @width = v if v
      when :path
        @path = v if v
      when :file
        @file = v if v
      when :actions
        if v.kind_of?(Array)
          @actions = v
        else
          raise StandardError, "Bad actions format"
        end
      else
        raise StandardError, "Bad parameter (#{k})"
      end
    end
    unless @width && @height || dummy?
      if @file || @path
        if @file.kind_of?(StringIO)
          @img = Magick::ImageList.new
          @file.rewind
          @img.from_blob(@file.read)
          @file.rewind
        else
          @img = Magick::ImageList.new(@file ? @file.path : @path)
        end
        #@img.from_blob(@file.read) # .rewind
        @width  = @img.columns
        @height = @img.rows
      end
    end
  end
  
  def dummy?
    ImageBuilder.dummy? || (!@path && !@img && !@file)
  end

  def read
    return nil if dummy?
    render_img
    @img.to_blob
  end

  def write(path)
    return false if dummy?
    render_img
    @img.write(path)
  end

  def rows
    return nil unless @height || !dummy?
    (@height ||= render_img.rows).round
  end
  
  def columns
    return nil unless @width || !dummy?
    (@width ||= render_img.columns).round
  end

  alias height rows
  alias width columns

  def resize!(s)
    # we do not zoom pixels
    return unless s < 1.0
    @img = nil # reset current rendered image
    @width  *= s
    @height *= s
    @actions << Proc.new {|img| img.resize!(s) }
  end
  
  def crop!(x,y,w,h)
    @img = nil # reset current rendered image
    @width  = [@width -x, w].min
    @height = [@height-y, h].min
    @actions << Proc.new {|img| img.crop!(x,y,[@img.columns-x, w].min,[@img.rows-y, h].min, true) }
  end
  
  def format=(fmt)
    return unless !dummy? && Magick.formats[fmt.upcase] =~ /w/
    @actions << Proc.new {|img| img.format = fmt.upcase; img }
  end
  
  def format
    render_img.format
  end
  
  def max_filesize=(size)
    @actions << Proc.new {|img| do_limit!(size) }
  end
  
  def do_limit!(size)
    return @img if @img.filesize <= size
    
    # Check real size
    tmp_path = Tempfile.new('tmp_img').path
    @img.write('jpeg:' + tmp_path)
    
    return @img if File.stat(tmp_path).size <= size
    
    # Change type to JPG and quality to 80
    if (@img.format == 'JPG' || @img.format == 'JPEG') && @img.quality > 80
      @img.write('jpeg:' + tmp_path) { self.quality = 80 }
    else
      @img.format = 'JPG'
      @img.write('jpeg:' + tmp_path) { self.quality = 80 }
    end
    ratio = File.stat(tmp_path).size.to_f / size
    return @img = Magick::ImageList.new(tmp_path) if ratio <= 1.0
    
    # Not enough ? Resize.
    ratio   = 1.0 / Math.sqrt(ratio)
    @width  *= ratio
    @height *= ratio
    @img.resize!(ratio)
    @img
  end
  
  def crop_min!(w,h,gravity=Magick::CenterGravity)
    @img = nil # reset current rendered image
    @width  = [@width ,w].min
    @height = [@height,h].min
    @actions << Proc.new {|img| img.crop!(gravity,[@img.columns,w].min,[@img.rows,h].min, true) }
  end

  def set_background!(opacity,w,h)
    @img = nil # reset current rendered image
    @width  = [@width ,w].max
    @height = [@height,h].max
    @actions << Proc.new do |img|
      bg = Magick::Image.new(w,h)
      bg.opacity = opacity
      bg.format = img.format
      img = bg.composite(img, Magick::CenterGravity, Magick::OverCompositeOp)
    end
  end

  # Transform into another format. If nil : do nothing.
  def transform!(tformat=nil)
    return self unless tformat
    @img = nil
    format = { :size=>:limit, :gravity=>Magick::CenterGravity }.merge(tformat)
    @pre, @post = format[:pre], format[:post]

    if format[:size] == :keep
      h,w = @height, @width
    else
      h,w = format[:height], format[:width]
    end
    if format[:scale]
      if h || w
        # scale is a pre-zoom before crop
        scale = format[:scale]
      else
        # we resize to scale
        h,w = @height*format[:scale], @width*format[:scale]
        # but we do not zoom
        scale = 1.0
        # ignore ':size' format if not height nor width was given
        format[:size] = :force
      end
    else
      scale = 1.0
    end
    if format[:ratio] && h && !w
      w = h / format[:ratio]
    elsif format[:ratio] && w && !h
      h = w * format[:ratio]
    end

    pw,ph = @width, @height
    raise StandardError, "image size or thumb size is null" if [w,h,pw,ph].include?(nil) || [w,h,pw,ph].min <= 0

    case format[:size]
    when :force
      crop_scale = [w.to_f/pw, h.to_f/ph].max
      if crop_scale > 1.0
        # we do not zoom. Fill with transparent background.
        crop_min!(w,h,format[:gravity])
        set_background!(Magick::MaxRGB, w, h)
      else
        resize!(crop_scale * scale)
        crop_min!(w, h,format[:gravity])
      end
    when :force_no_crop
      crop_scale = [w.to_f/pw, h.to_f/ph].min
      resize!(crop_scale * scale)
      crop_min!(w, h,format[:gravity])
      set_background!(Magick::MaxRGB, w, h)
    when :limit
      crop_scale = [w.to_f/pw, h.to_f/ph].min
      resize!(crop_scale * scale)
      crop_min!(w, h,format[:gravity])
    when :keep
    end
    self
  end

  def render_img
    raise IOError, 'MagickDummy cannot render image' if ImageBuilder.dummy?
    unless @img
      if @file
        @img = Magick::ImageList.new
        @file.rewind # we have read this file once when saving to disk
        @img.from_blob(@file.read)
        @file.rewind
      elsif @path
        @img = Magick::ImageList.new(@path)
      else
        raise IOError, 'Cannot render image without path or file'
      end
      if @pre
        @pre = [@pre].flatten
        @pre.each do |a|
          @img = a.call(@img)
        end
      end

      if @actions
        @actions.each do |a|
          @img = a.call(@img)
        end
      end

      if @post
        @post = [@post].flatten
        @post.each do |a|
          @img = a.call(@img)
        end
      end
    end
    @img
  end
end