VRM image file extract tools (Ruby)

vrm-extract.rb

#!/usr/bin/ruby -Ks
# Copyright (C) 2020 Yakumo Sayo. All rights reserved.
# Dual Licence (BSD 2-Crause or GPLv3)

require 'pathname'
require 'JSON'
buf = File.open(ARGV[0], "rb")

def read_uint32(buffer)
    buffer.read(4).bytes.reverse.inject(0){|s,i| s*256 + i}
end
def chunk_read(buffer)
    chunk_length = read_uint32(buffer)
    chunk_type = read_uint32(buffer)
    buffer.read(chunk_length)
end


magic = read_uint32(buf)
version = read_uint32(buf)
file_length = read_uint32(buf)

puts("magic:#{magic}, version:#{version}, length:#{file_length}")

json = chunk_read(buf)


basename = File.basename(ARGV[0])
json_file = "#{basename}.json"
File.open(json_file, mode = "w"){|f|
    f.write json
}
puts "written: #{json_file}"
bin = chunk_read(buf)

=begin
bin_name = "#{basename}.01.bin"
File.open(json_file, mode = "wb"){|f|
    f.write(bin, bin.size)
}
puts "written: #{bin_name}"
=end

gltf = JSON.parse(json)
  
gltf['images'].map{|x| 
  x['bufferView'] 
}.map{|i|
    view = gltf['bufferViews'][i]
    png_data = bin[ view['byteOffset'],  ] 
    snum = format("%02d", i)
    filename = "#{basename}-#{snum}.png"
    File.open(filename, mode = "wb"){|f|
        f.write(bin[view['byteOffset'], view['byteLength']], view['byteLength'])
    }
    puts "written: #{filename}"
}