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.



18
19
20
21
22
 
# 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



29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
 
# 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



83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
 
# 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