[Insight-users] DicomSeriesReadImageWrite2_Problem to read dcmSeries

[Mathieu Malaterre]

Daniela,

  Forget my latest comment. By default PNG is lossless. You have to
use 3rd party tool to reduce -say- the number of color (see pngquant)
in order to do 'lossy' compression.
  So you are *completely* safe when using PNG from matlab.

Sorry for the noise,
-Mathieu

On Tue, May 25, 2010 at 5:47 PM, Daniela Sacchetto
<danysunflower at hotmail.it> wrote:
> Mathieu, a question for you: how can I know if Matlab png format is lossless
> or lossy?
>  I don't have any information to help me and I found on wikipedia this
> definition:
>
> "
> Portable Network Graphics (PNG) is a bitmapped image format that employs
> lossless data compression.
>
> [...]
>
> PNG uses a 2-stage compression process:
>
> pre-compression: filtering (prediction)
> compression: DEFLATE
>
> PNG uses a non-patented lossless data compression method known as DEFLATE,
> which is the same algorithm used in the zlib compression library.
>
> "
>
> But I don't find anything about PNG lossy compression....
> Really, it is a simple curiosity because I could save my image in PGM or PPM
> how to told me...but, since I'm not expert in this field, I would know
> something about it.
>
> Thanks for your time,
> Regards
> Daniela
>
>> From: mathieu.malaterre at gmail.com
>> Date: Tue, 25 May 2010 17:28:01 +0200
>> Subject: Re: [Insight-users] DicomSeriesReadImageWrite2_Problem to read
>> dcmSeries
>> To: luis.ibanez at kitware.com
>> CC: danysunflower at hotmail.it; insight-users at itk.org
>>
>> On Tue, May 25, 2010 at 5:21 PM, Luis Ibanez <luis.ibanez at kitware.com>
>> wrote:
>> > If keeping image precision is critical for your
>> > application, you may want to save the images
>> > in a lossless format (e.g. png) and still do the
>> > same trick in ITK to read the series of slices.
>>
>> Just for reference, PNG allow both lossless and lossy compression
>> mechanism. You should pick the right one.
>>
>> Otherwise go for the old timer: PGM/PPM :)
>>
>> --
>> Mathieu
>
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-- 
Mathieu