92 lines
3.7 KiB
Ruby
92 lines
3.7 KiB
Ruby
# frozen_string_literal: true
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# This file contains code derived from
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# https://github.com/dim/ruby-imagespec/blob/f2f3ce8bb5b1b411f8658e66a891a095261d94c0/lib/image_spec/parser/swf.rb
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#
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# Copyright (c) 2020, Danbooru Project contributors
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# Copyright (c) 2008, Brandon Anderson (anderson.brandon@gmail.com)
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# All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or without modification,
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# are permitted provided that the following conditions are met:
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#
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# Redistributions of source code must retain the above copyright notice,
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# this list of conditions and the following disclaimer.
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#
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# Redistributions in binary form must reproduce the above copyright notice,
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# this list of conditions and the following disclaimer in the documentation
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# and/or other materials provided with the distribution.
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#
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# Neither the name of the original author nor the names of contributors
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# may be used to endorse or promote products derived from this software
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# without specific prior written permission.
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#
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#
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class MediaFile::Flash < MediaFile
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def dimensions
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# Read the entire stream into memory because the
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# dimensions aren't stored in a standard location
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contents = File.read(file.path, binmode: true).force_encoding("ASCII-8BIT")
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# Our 'signature' is the first 3 bytes
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# Either FWS or CWS. CWS indicates compression
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signature = contents[0..2]
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# SWF version
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_version = contents[3].unpack('C').join.to_i
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# Determine the length of the uncompressed stream
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length = contents[4..7].unpack('V').join.to_i
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# If we do, in fact, have compression
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if signature == 'CWS'
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# Decompress the body of the SWF
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body = Zlib::Inflate.inflate(contents[8..length])
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# And reconstruct the stream contents to the first 8 bytes (header)
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# Plus our decompressed body
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contents = contents[0..7] + body
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end
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# Determine the nbits of our dimensions rectangle
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nbits = contents.unpack('C' * contents.length)[8] >> 3
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# Determine how many bits long this entire RECT structure is
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rectbits = 5 + nbits * 4 # 5 bits for nbits, as well as nbits * number of fields (4)
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# Determine how many bytes rectbits composes (ceil(rectbits/8))
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rectbytes = (rectbits.to_f / 8).ceil
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# Unpack the RECT structure from the stream in little-endian bit order, then join it into a string
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rect = contents[8..(8 + rectbytes)].unpack("#{'B8' * rectbytes}").join
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# Read in nbits incremenets starting from 5
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dimensions = []
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4.times do |n|
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s = 5 + (n * nbits) # Calculate our start index
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e = s + (nbits - 1) # Calculate our end index
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dimensions[n] = rect[s..e].to_i(2) # Read that range (binary) and convert it to an integer
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end
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# The values we have here are in "twips"
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# 20 twips to a pixel (that's why SWFs are fuzzy sometimes!)
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width = (dimensions[1] - dimensions[0]) / 20
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height = (dimensions[3] - dimensions[2]) / 20
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[width, height]
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end
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memoize :dimensions
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end
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