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From: "Bad Badtz" <badtzbad@hotmail.com>
To: pjmonty@csi.com, tiff@olympiakos.com
Subject: Re: Partial Extraction of a Scanline?
Date: Wed, 02 Jan 2002 15:02:16 +0800
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Hi,

Thanks Peter for responding to my previous mail!

Take for example, I would like to view a part of a striped image with 
scanline size = 32,000 pixels on a screen 1024 by 768.

Using ReadScanline will return me all 32,000pixels when in fact only 1024 
pixels can be seen on screen. The other 30,000+ pixels are rather useless. I 
was thinking won't it be better if I can just get that 1024 pixels instead 
of the whole scanline? How should I go about modifying the code to read 
partial scanline? Please enlighten me!

Thanks!



>From: Peter Montgomery <pjmonty@csi.com>
>To: tiff@olympiakos.com
>Subject: Re: Partial Extraction of a Scanline?
>Date: Sun, 30 Dec 2001 20:34:39 -0800
>
>Bad,
>
>     I don't believe that you can read a partial scanline, however,
>others on the list may correct this.  If the image were tiled, you could
>of course read it a tile at a time and build your own scanline.
>However, I am curious just how big can your scanline possibly be?  An
>image that is 32,0000 pixels across (mighty big in my opinion) and RGBA
>would still take up only 128 KB of memory.  Certainly this wouldn't take
>long to allocate at all.  Even if the image were 1 million pixels across
>and RGBA, it would still take only 4 MB of memory.  Just how big are
>these images that allocating a buffer big enough to hold it would take
>any appreciable amount of time?
>
>     Thanks,
>     PeterM
>
>----- Original Message -----
>From: "Bad Badtz" <badtzbad@hotmail.com>
>To: <tiff@olympiakos.com>
>Sent: Sunday, December 30, 2001 8:15 PM
>Subject: Partial Extraction of a Scanline?
>
>
> >
> > Hi!
> >
> > I understand that LibTIFF provides APIs to read the scanlines, strips
>or
> > tiles of a TIFF or GeoTIFF image. However when reading just one
>scanline of
> > a striped image that is rather huge (a few GBs), a big buffer needs to
>be
> > created and it will take a long time.
> >
> > Is there anyway I can read parts of a scanline instead of the whole
> > scanline?
>
>
>To subscribe or unsubscribe email tiff-request@olympiakos.com with 
>subscribe
>or unsubscribe in the email body.  Libtiff home page: 
>http://www.libtiff.org


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