Class: Rixmap::Format::PNG::AdaptiveFilter

Inherits:
Object
  • Object
show all
Defined in:
lib/rixmap/format/png/imageio.rb

Overview

スキャンライン用フィルタ実装.

FIXME これ超重い気がする

See Also:

Instance Method Summary collapse

Constructor Details

#initialize(mode) ⇒ AdaptiveFilter

デフォルトフィルタ実装を初期化します.

Parameters:



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# File 'lib/rixmap/format/png/imageio.rb', line 18

def initialize(mode)
  @prev = Rixmap::Binary.new()
  @mode = mode
  @size = mode.channels.size
end

Instance Method Details

#filt(line, method = ADAPTIVEFILTER_NONE) ⇒ Array

フィルタ関数

Parameters:

  • line (Array) —

    対象スキャンライン

  • method (Integer) (defaults to: ADAPTIVEFILTER_NONE) —

    フィルタメソッド

Returns:

  • (Array) —

    フィルタ処理後スキャンライン



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# File 'lib/rixmap/format/png/imageio.rb', line 29

def filt(line, method = ADAPTIVEFILTER_NONE)
  base_line = Rixmap::Binary.new(line)
  filt_line = Rixmap::Binary.new()
  case method
  when ADAPTIVEFILTER_NONE
    filt_line += base_line
  when ADAPTIVEFILTER_SUB
    base_line.each_with_index do |byte, i|
      prev_idx  = i - @size
      prev_byte = if prev_idx < 0
                    0
                  else
                    base_line[prev_idx]
                  end
      filt_line[i] = byte - prev_byte
    end
  when ADAPTIVEFILTER_UP
    base_line.each_with_index do |byte, i|
      filt_line[i] = byte - @prev[i].to_i
    end
  when ADAPTIVEFILTER_AVERAGE
    base_line.each_with_index do |byte, i|
      before_idx  = i - @size
      before_byte = if before_idx < 0
                      0
                    else
                      base_line[before_idx]
                    end
      prev_byte = @prev[i].to_i
      filt_line[i] = byte - ((before_byte + prev_byte) / 2.0).floor
    end
  when ADAPTIVEFILTER_PEATH
    base_line.each_with_index do |byte, i|
      before_idx  = i - @size
      byte_a, byte_c = if before_idx < 0
                         [0, 0]
                       else
                         [base_line[before_idx], @prev[before_idx].to_i]
                       end
      byte_b = @prev[i].to_i
      filt_line[i] = byte - self.peath_predicator(byte_a, byte_b, byte_c)
    end
  else
    raise NotImplementedError.new("Unsupported Filter Method: #{method}")
  end

  @prev = base_line
  filt_line.unshift(method)
  return filt_line
end

#recon(line) ⇒ Object

復元関数

Parameters:

  • line (Array) —

    対象スキャンライン



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# File 'lib/rixmap/format/png/imageio.rb', line 83

def recon(line)
  base_line  = Rixmap::Binary.new(line)
  recon_line = Rixmap::Binary.new
  method = base_line.shift

  case method
  when ADAPTIVEFILTER_NONE
    recon_line += base_line
  when ADAPTIVEFILTER_SUB
    base_line.each_with_index do |byte, i|
      prev_idx  = i - @size
      prev_byte = if prev_idx < 0
                    0
                  else
                    recon_line[prev_idx]
                  end
      recon_line[i] = byte + prev_byte
    end
  when ADAPTIVEFILTER_UP
    base_line.each_with_index do |byte, i|
      recon_line[i] = byte + @prev[i].to_i
    end
  when ADAPTIVEFILTER_AVERAGE
    base_line.each_with_index do |byte, i|
      before_idx  = i - @size
      before_byte = if before_idx < 0
                      0
                    else
                      recon_line[before_idx]
                    end
      prev_byte = @prev[i].to_i
      recon_line[i] = byte + ((before_byte + prev_byte) / 2.0).floor
    end
  when ADAPTIVEFILTER_PEATH
    base_line.each_with_index do |byte, i|
      before_idx  = i - @size
      byte_a, byte_c = if before_idx < 0
                         [0, 0]
                       else
                         [recon_line[before_idx], @prev[before_idx].to_i]
                       end
      byte_b = @prev[i].to_i
      recon_line[i] = byte + self.peath_predicator(byte_a, byte_b, byte_c)
    end
  else
    raise NotImplementedError.new("Unsupported Filter Method: #{method}")
  end

  @prev = recon_line
  return recon_line
end