[Re: [Insight-users] Re: Problem with lossless JPEG compression in GDCMImageIO]

[Jean-Pierre Roux]

-------- Original Message --------
Subject: 	Re: [Insight-users] Re: Problem with lossless JPEG compression 
in GDCMImageIO
Date: 	Tue, 25 Sep 2007 09:22:53 +0200
From: 	Jean-Pierre Roux <jpr at creatis.univ-lyon1.fr>
To: 	Steve M. Robbins <steve at sumost.ca>
CC: 	Pechin Lo <pechin at gmail.com>, insight-users at itk.org
References: 
<3cb9eaf00709241144y4551a419xb9e60806d6aea1da at mail.gmail.com> 
<3cb9eaf00709241450i54afb9d0w352a5d05cdbe7bb2 at mail.gmail.com> 
<20070925011834.GH29483 at sumost.ca>



Steve M. Robbins wrote:
> On Mon, Sep 24, 2007 at 11:50:05PM +0200, Pechin Lo wrote:
>   
>> After some tweaking around, I found out that JPEG compression works provided
>> that the minimum difference between two pixels is 2.
>> For example, if I have an image that only consists of n and n+1, the saved
>> image will only contains the value n.
>> However, if the image consists of value n and n+2, then the saved image will
>> contains both n and n+2.
>> In other words, the image will stores fine if I multiply it by a factor of
>> 2.
>>
>> Can someone please tell me why is this happening?
>>     
>
> I'm not familiar with the code in question, but is it possible
> that you're using a lossy JPEG compression?
> 
  
Oops!
gdcm only performs lossless compression ...
We use the Independent JPEG Group's (IJG) libjpeg version 6b.

I'll try to find if there is any bug report about it.

Jean-Pierre Roux

> -Steve
>   
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