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102 lines
2.4 KiB
Ruby
Executable file
102 lines
2.4 KiB
Ruby
Executable file
#!/usr/bin/env ruby
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# Copyright 2024 Google LLC
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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require 'RMagick'
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im = Magick::ImageList.new(ARGV[0]).first
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current_data = 0
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current_alpha = 0
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data = []
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alpha = []
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0.upto(im.rows - 1) do |r|
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0.upto(maxcol = (im.columns - 1)) do |c|
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pix = im.pixel_color(c, r)
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if pix.intensity == 0 # black
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current_data |= (1 << (c % 8))
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end
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if pix.opacity == 0 # opaque
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current_alpha |= (1 << (c % 8))
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end
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if c % 8 == 7 or c == maxcol
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data << current_data
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alpha << current_alpha
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current_data = 0
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current_alpha = 0
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end
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end
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end
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packed_data, packed_alpha = [data, alpha].map do |raw|
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i = 0
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packet_start = 0
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out = []
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while i < raw.size
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if i < raw.size - 1 and raw[i] == raw[i+1]
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# output literal packet
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if i > packet_start
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out << (i - packet_start - 1)
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out += raw[packet_start..i-1]
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end
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# start a run
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packet_start = i
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while raw[i] == raw[i+1] and (i - packet_start) < 127
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i += 1
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end
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out << -(i - packet_start)
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out << raw[i]
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# next packet starts at next byte
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packet_start = i + 1
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elsif (i - packet_start) == 127 or i == raw.size - 1
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# too many literal bytes, output and move to next packet
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out << (i - packet_start)
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out += raw[packet_start..i]
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packet_start = i + 1
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end
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i += 1
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end
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unpacked_size = 0
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i = 0
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while i < out.size
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if out[i] > 0
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unpacked_size += out[i] + 1
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i += out[i] + 2
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else
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unpacked_size += 1 - out[i]
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i += 2
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end
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end
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#puts unpacked_size
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#puts out.size
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out
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end
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ARGV[0] =~ /(.*)\..*$/
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file_name = "#{$1}.packbits"
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puts "Wrote #{file_name}"
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puts "Compressed image size is: " + packed_data.size.to_s
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File.open(file_name, 'w') do |file|
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file.print 'PBPB'
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file.print [im.columns, im.rows].pack('n*')
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file.print [packed_data.size].pack('N*')
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file.print packed_data.pack('c*')
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end
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