From: Robert Klemme <shortcutter@...>
Date: 2009-12-03T17:17:58+09:00
Subject: Re: Encoding/decoding a image as Base64 (fails under Ruby1.9 but 	works under Ruby1.8)

2009/12/3 Iņaki Baz Castillo <ibc@aliax.net>:
> Hi, the folowing code encodes and decodes a image file as Base64:
>
> - Encode "icon.png" in Base64 as "base64.txt":
> --------------------------------------
>  File.open("base64.txt","w") do |file|
>    file.write [open("icon.png").read].pack("m")
>  end
> --------------------------------------
>
> - Decode "base64.txt" as a PNG "new_icon.png" file:
> --------------------------------------
>  File.open('new_icon.png', 'wb') do |file|
>    file << (IO.readlines('base64.txt').to_s.unpack('m')).first
>  end
> --------------------------------------
>
>
> It works perfectly under Ruby1.8 (after encoding and decoding "icon.png" is
> exatcly the same as "new_icon.png", the same binay file).
>
> However running under Ruby1.9 the result is different since "new_icon.png" is
> a corrupted image file. When I try to open it with a image viewer I get this
> error (under Linux):
>
>  libpng warning: gAMA: CRC error
>  libpng error: PNG unsigned integer out of range.
>
>
> Which is the difference when using Ruby1.9? how to solve it?
> Thanks a lot.

One thing strikes odd: you are not reading the file in binary mode.
It may be that 1.9 punishes you for that.  You probably rather want

File.open("base64.txt","w") do |file|
  file.write [File.open("icon.png", "rb") {|io| io.read}].pack("m")
end

You can simplify decoding as

File.open('new_icon.png', 'wb') do |file|
   file.write(File.read('base64.txt').unpack('m').first)
end

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
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