Class: ImageSpec::Parser::SWF
- Inherits:
-
Object
- Object
- ImageSpec::Parser::SWF
- Defined in:
- lib/parser/swf.rb
Constant Summary collapse
- CONTENT_TYPE =
'application/x-shockwave-flash'
Class Method Summary collapse
Class Method Details
.attributes(stream) ⇒ Object
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# File 'lib/parser/swf.rb', line 11 def self.attributes(stream) width, height = dimensions(stream) {:width => width, :height => height, :content_type => CONTENT_TYPE} end |
.detected?(stream) ⇒ Boolean
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# File 'lib/parser/swf.rb', line 16 def self.detected?(stream) stream.rewind stream.read(3) =~ /(F|C)WS/ ? true : false end |
.dimensions(stream) ⇒ Object
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# File 'lib/parser/swf.rb', line 21 def self.dimensions(stream) # Read the entire stream into memory because the # dimensions aren't stored in a standard location stream.rewind contents = stream.read # Our 'signature' is the first 3 bytes # Either FWS or CWS. CWS indicates compression signature = contents[0..2] # Determine the length of the uncompressed stream length = contents[4..7].unpack('V').join.to_i # If we do, in fact, have compression if signature == 'CWS' # Decompress the body of the SWF body = Zlib::Inflate.inflate( contents[8..length] ) # And reconstruct the stream contents to the first 8 bytes (header) # Plus our decompressed body contents = contents[0..7] + body end # Determine the nbits of our dimensions rectangle nbits =contents.unpack('c'*contents.length)[8] >> 3 # Determine how many bits long this entire RECT structure is rectbits = 5 + nbits * 4 # 5 bits for nbits, as well as nbits * number of fields (4) # Determine how many bytes rectbits composes (ceil(rectbits/8)) rectbytes = (rectbits.to_f / 8).ceil # Unpack the RECT structure from the stream in little-endian bit order, then join it into a string rect = contents[8..(8 + rectbytes)].unpack("#{'B8' * rectbytes}").join() # Read in nbits incremenets starting from 5 dimensions = Array.new 4.times do |n| s = 5 + (n * nbits) # Calculate our start index e = s + (nbits - 1) # Calculate our end index dimensions[n] = rect[s..e].to_i(2) # Read that range (binary) and convert it to an integer end # The values we have here are in "twips" # 20 twips to a pixel (that's why SWFs are fuzzy sometimes!) width = (dimensions[1] - dimensions[0]) / 20 height = (dimensions[3] - dimensions[2]) / 20 # If you can't figure this one out, you probably shouldn't have read this far return [width, height] end |