Class: ZSteg::Masker

Inherits:
Object
  • Object
show all
Defined in:
lib/zsteg/masker.rb

Instance Method Summary collapse

Constructor Details

#initialize(image, params = {}) ⇒ Masker

Returns a new instance of Masker.



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# File 'lib/zsteg/masker.rb', line 5

def initialize image, params = {}
  @src = image.is_a?(ZPNG::Image) ? image : ZPNG::Image.load(image)
  @masks = params[:masks] || {}
  @mask = params[:mask] || @masks[:all]
  @normalize = params[:normalize]
  [:r, :g, :b, :a].each{ |x| @masks[x] ||= @mask }
end

Instance Method Details

#mask(params = {}) ⇒ Object 



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# File 'lib/zsteg/masker.rb', line 13

def mask params = {}
  dst = ZPNG::Image.new :width => @src.width, :height => @src.height
  rm, gm, bm, am = @masks[:r], @masks[:g], @masks[:b], @masks[:a]
  rd, gd, bd, ad = rm==0?1:rm, gm==0?1:gm, bm==0?1:bm, am==0?1:am
  # duplicate loops for performance reason
  if @normalize
    if rm == 0 && gm == 0 && bm == 0 && am != 0
      # alpha2grayscale
      @src.each_pixel do |c,x,y|
        c.r = c.g = c.b = (c.a & am) * 255 / ad
        c.a = 0xff
        dst[x,y] = c
      end
    else
      # normal operation
      @src.each_pixel do |c,x,y|
        #TODO: c.to_depth(8)
        # further possible optimizations:
        # a) precalculate (255 / Xm)
        c.r = (c.r & rm) * 255 / rd
        c.g = (c.g & gm) * 255 / gd
        c.b = (c.b & bm) * 255 / bd
        c.a = (c.a & am) * 255 / ad
        dst[x,y] = c
      end
    end
  else
    @src.each_pixel do |c,x,y|
      #TODO: c.to_depth(8)
      c.r &= rm
      c.g &= gm
      c.b &= bm
      c.a &= am
      dst[x,y] = c
    end
  end
  dst
end