[GRASSLIST:371] Re: Import jpg with r.in.gdal size problem

[Jonathan Greenberg]

Silvia:

	As a rule, JPEGs are a very bad idea for remotely sensed imagery,
since they are lossy.  Unfortunately, you are going to run into similar
problems with other programs, which will also convert the jpgs into a
lossless format (e.g. arc, imagine, envi).  15gb is a pretty small hard
drive these days -- I just found a 250gb internal HD for $60 (with a rebate,
I'm assuming).  Get more storage!

--j

--

Jonathan A. Greenberg, PhD
NRC Research Associate
NASA Ames Research Center
MS 242-4
Moffett Field, CA 94035-1000
Phone: 415-794-5043
AIM: jgrn3007
MSN: jgrn3007 at hotmail.com

-----Original Message-----
From: owner-GRASSLIST at baylor.edu [mailto:owner-GRASSLIST at baylor.edu] On
Behalf Of Silvia Franceschi
Sent: Friday, March 24, 2006 11:29 AM
To: Laurent Courty
Cc: grasslist at baylor.edu
Subject: [GRASSLIST:370] Re: Import jpg with r.in.gdal size problem

That means that GRASS converts them into GRASS maps that think to be
lossless 
but obviously can not ricreate what jpeg didn't have? Please correct me if I

am wrong.
So what is the solution? I can't use this data because I can't exchange them

with other collegues, what can I do? they say to me that the original data 
are 700 MB and now they are 15 GB, that means that they have to have a lot
of 
space on their pc, but it isn't. 
My real problem is that the workstations have not enought space on harddisk 
and so it is impossible for me to give them the data.

Thanks

Silvia 


> > Hi everyone,
> > I have imported some jpg files (230 orthophoto of my region) in GRASS
> > using the command r.in.gdal. The original size of the data is about 3-5
> > MB with a text file of about 150 B. When I import the data in GRASS I
> > obtain files of 75-100 MB and that means too much space to disk.
> > Do someone know if there is a way to compress them? Now I have a
location
> > of 15 GB and I can't manage it.
> >
> > Please help me...
> >
> > Thanks,
> > Silvia
>
> Hi,
>
> jpeg compress a lot but cause loss of quality. AFAIK, GRASS
> automatically apply a lossless compression on raster.
> The size is bigger than jpeg.
>
> Laurent

-- 
____________________________________________________________________________
HydroloGIS - Environmental Open Source Solutions
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Silvia Franceschi
Environmental Engineer
tel: +390471068066
mobile:  +393384501332
email: silvia.franceschi at hydrologis.com
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