Groups > Corel > Corel PhotoPaing X3 > Re: Magenta color blotches... is the CPT file format truly lossless?




Re: Magenta color blotches... is the CPT file format truly
lossless?

Re: Magenta color blotches... is the CPT file format truly lossless?
Wed, 19 Mar 2008 11:41:46 -040
Sean to answer you question about lossless compression only.  The CPT file 
format is a proprietary lossless file compression.  To test any degradation 
one has to use the CPT file format and compare it to an uncompressed TIF 
file.


"Sean" <azurepicTHISISFORSPAM@yahooSPAM.com> wrote in message 
news:47e04f15_2@cnews...
> Jeff,
>
> I have tested your file, never making it into a jpg, to remove that from 
> the
> equation and re-attach it after multiple saves in PP.  It has clearly
> degraded.  So I attached my default color management settings for CMYK 
> work,
> though I leave files in RGB until conversion is needed.
>
> Then I repeated the test (test2.png) with the color management 
> import/export
> settings changed as per the 'losslesscm' screen capture.  There appears to
> be no change after multiple saves.
>
> So, here's my thinking (obviously flawed somewhere):  I left import color
> management on since I thought that would improve my likelihood of getting
> extra color info when importing files from cameras and other sources.  I
> left export color management off because any jpgs exported with this on 
> are
> huge with all that color info included.  I do web work from time to time 
> and
> also save out files for email to other people, etc.  I had no idea that 
> save
> and load, open and close with CPT's and CDR's were causing color changes 
> to
> my files.
>
> As for the other comment, that starting with jpg files means they continue
> to degrade... are you guys suggesting that I need to explicitly convert a
> jpg into a CPT or tiff before I import it into DRAW?  Or save it as a tiff
> before saving as a CPT?  I don't see that as a likely or realistic 
> workflow.
> The CDR and CPT file formats are supposed to be lossless, and I've never
> read that it matters what original format the files are in.  I have been
> using DRAW/PP since version 9, nearly nine years now, so I'm not a total
> newcomer.
>
> If this is truly the case with color management, that either both import
> export arrows need to be on (assumption, not tested) or both off (tested),
> then there should be a warning when we set it otherwise.  In fact, I 
> notice
> that the 'Optimized for desktop printing' color management settings have
> only the import arrow enabled.  So using this profile, we could also 
> expect
> bitmap degradation (not tested)?
>
> I appreciate your input.
> Sean
>
> "Jeff Harrison" <test@test.com> wrote in message 
> news:47e01451$1_3@cnews...
>> Hi Sean,
>>
>> I applaud your efforts to want to ensure everything is OK.
>>
>> Here is a test file I'd like you to quickly try, you are familiar with
>> your testing process.
>>
>> It's here are lossless 24 bit PNG, and covers pretty much the whole
>> spectrum. If anomalies appear, they should be revealed more readily in
>> this case.
>>
>> I see the blotches in your prev. examples, but for the moment let's
>> leave jpeg out of the equation - at every stage.
>>
>>
>> Jeff
>>
> 



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