70 lines
1.8 KiB
Ruby
70 lines
1.8 KiB
Ruby
class APNGInspector
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attr_reader :frames
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PNG_MAGIC_NUMBER = ["89504E470D0A1A0A"].pack('H*')
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def initialize(file_path)
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@file_path = file_path
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@corrupted = false
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@animated = false
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end
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#Calls associated block for each PNG chunk
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#parameters passed are |chunk_name, chunk_length, file_descriptor|
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#returns true if file is read succesfully from start to IEND, false otherwise.
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def each_chunk
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iend_reached = false
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File.open(@file_path, 'rb') do |file|
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return false if file.read(8) != PNG_MAGIC_NUMBER
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while chunkheader = file.read(8)
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return false if chunkheader.to_s.length != 8
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chunk_len, chunk_name = chunkheader.unpack("Na4")
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current_pos = file.tell
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yield chunk_name, chunk_len, file
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if chunk_name == "IEND"
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iend_reached = true
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break
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end
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file.seek(current_pos+chunk_len+4, IO::SEEK_SET)
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end
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end
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return iend_reached
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end
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def inspect!
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actl_corrupted = false
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read_success = each_chunk do |name, len, file|
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if name == 'acTL'
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if len != 8 then
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actl_corrupted = true
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else
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framedata = file.read(4)
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if framedata.to_s.length != 4
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actl_corrupted = true
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else
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framecount = framedata.unpack("N")[0]
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if framecount < 1
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actl_corrupted = true
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else
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@animated = true
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@frames = framecount
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end
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end
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end
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end
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end
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@corrupted = !read_success || actl_corrupted
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return !@corrupted
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end
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def corrupted?
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@corrupted
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end
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def animated?
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!@corrupted && @animated && @frames > 1
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end
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end |