From: "Iñaki Baz Castillo" <ibc@...>
Date: 2009-12-03T18:43:52+09:00
Subject: Re: Encoding/decoding a image as Base64 (fails under Ruby1.9 but works under Ruby1.8)

El Jueves, 3 de Diciembre de 2009, Robert Klemme escribió:
> 2009/12/3 Iñaki 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


That makes lot of sense!
Thanks.

-- 
Iñaki Baz Castillo <ibc@aliax.net>