Details Ticket 978


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Serial Number 978
Subject Raster maps in GRASS monitor show unwanted color stripe on left side
Area bug
Queue grass
Requestors neteler@itc.it
Owner none
Status resolved
Last User Contact Mon Mar 25 22:07:26 2002 (6 yr ago)
Current Priority 30
Final Priority 70
Due No date assigned
Last Action Tue Mar 26 17:46:57 2002 (6 yr ago)
Created Mon Mar 25 13:49:37 2002 (6 yr ago)

Transaction History Ticket 978


Mon, Mar 25 2002 13:49:37    Request created by mneteler  
Subject: Raster maps in GRASS monitor show unwanted color stripe on left side
Platform: Linux/Intel
grass downloaded at: CVS Server, Germany
grass binary for platform: I compiled the sources myself
grass sources source: (latest) GRASS from CVS

Hi,

what I discover some time ago and looks like a small map shift (or whatever):
Raster maps in GRASS monitor sometimes show unwanted color stripe on left side.
For illustration I have generated a snapshot:
http://mpa.itc.it/markus/tmp/grassmon_stripe.jpg
(Lat/Long).

This appears also in projected locations but not always (I do not know a way
yet
to reproduce it with Spearfish)

Markus

Mon, Mar 25 2002 15:03:51    Mail sent by bernhard  
mneteler wrote (Mon, Mar 25 2002 13:49:37):

> Subject: Raster maps in GRASS monitor show unwanted color stripe on left side
> 
> Platform: Linux/Intel
> grass downloaded at: CVS Server, Germany
> grass binary for platform: I compiled the sources myself
> grass sources source: (latest) GRASS from CVS
> 
> Hi,
> 
> what I discover some time ago and looks like a small map shift (or whatever):
> Raster maps in GRASS monitor sometimes show unwanted color stripe on left side.
> 
> For illustration I have generated a snapshot:
> http://mpa.itc.it/markus/tmp/grassmon_stripe.jpg
> (Lat/Long).
> 
> This appears also in projected locations but not always (I do not know a way
yet
> to reproduce it with Spearfish)

How did you import the data?
I've noticed this too with GTOPO30 data and alwasy thought it could be
a non skipped fill or header data problem...
Mon, Mar 25 2002 17:42:49    Mail sent by neteler@itc.it  
Return-Path <neteler@itc.it>
Delivered-To grass-bugs@lists.intevation.de
Date Mon, 25 Mar 2002 17:42:45 +0100
From Markus Neteler <neteler@itc.it>
To Bernhard Reiter via RT <grass-bugs@intevation.de>
Subject Re: [bug #978] (grass) Raster maps in GRASS monitor show unwanted color stripe on left side
Message-ID <20020325174245.O29083@itc.it>
References <20020325140351.4BDD413967@lists.intevation.de>
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Content-Type text/plain; charset=us-ascii
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In-Reply-To <20020325140351.4BDD413967@lists.intevation.de>; from grass-bugs@intevation.de on Mon, Mar 25, 2002 at 03:03:51PM +0100
X-Spam-Status No, hits=0 required=5 tests=
On Mon, Mar 25, 2002 at 03:03:51PM +0100, Bernhard Reiter via RT wrote:
> mneteler wrote (Mon, Mar 25 2002 13:49:37):
> 
> > Subject: Raster maps in GRASS monitor show unwanted color stripe on left
side
> > 
> > Platform: Linux/Intel
> > grass downloaded at: CVS Server, Germany
> > grass binary for platform: I compiled the sources myself
> > grass sources source: (latest) GRASS from CVS
> > 
> > Hi,
> > 
> > what I discover some time ago and looks like a small map shift (or whatever):
> > Raster maps in GRASS monitor sometimes show unwanted color stripe on left
side.
> > 
> > For illustration I have generated a snapshot:
> > http://mpa.itc.it/markus/tmp/grassmon_stripe.jpg
> > (Lat/Long).
> > 
> > This appears also in projected locations but not always (I do not know a
way yet
> > to reproduce it with Spearfish)
> 
> How did you import the data?
> I've noticed this too with GTOPO30 data and alwasy thought it could be
> a non skipped fill or header data problem...

As written above, this problem appears for different data.
The GLOBE DEM I imported with a recent GDAL (r.in.gdal). It
is not a shift in the data itself but only (I am quite sure) related
to the monitor display.

It also appears with other data from different sources, but
 - only sometimes (no idea when, certainly I try to find any systematic
   error)
 - when left and right border of the monitor are black due to map extend/
   monitor ratio

Markus

 


Mon, Mar 25 2002 22:07:26    Mail sent by glynn.clements@virgin.net  
Return-Path <glynn.clements@virgin.net>
Delivered-To grass-bugs@lists.intevation.de
From Glynn Clements <glynn.clements@virgin.net>
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Message-ID <15519.37168.685935.713394@cerise.nosuchdomain.co.uk>
Date Mon, 25 Mar 2002 21:05:52 +0000
To Request Tracker <grass-bugs@intevation.de>
Cc grass5@grass.itc.it
Subject Re: [GRASS5] [bug #978] (grass) Raster maps in GRASS monitor show unwanted color stripe on left side
In-Reply-To <20020325124937.6FC6E139C9@lists.intevation.de>
References <20020325124937.6FC6E139C9@lists.intevation.de>
X-Mailer VM 6.94 under 21.4 (patch 4) "Artificial Intelligence (candidate #1)" XEmacs Lucid
X-Spam-Status No, hits=0 required=5 tests=
Request Tracker wrote:

> Subject: Raster maps in GRASS monitor show unwanted color stripe on left side
> what I discover some time ago and looks like a small map shift (or whatever):
> Raster maps in GRASS monitor sometimes show unwanted color stripe on left side.
> 
> For illustration I have generated a snapshot:
> http://mpa.itc.it/markus/tmp/grassmon_stripe.jpg
> (Lat/Long).
> 
> This appears also in projected locations but not always (I do not know a way
yet
> to reproduce it with Spearfish)

AFAICT, this is due to rounding error in src/libes/display/cnversions.c
(D_do_conversions et al). By simplifying the computations in that file, I
can get the problem to go away. However, there might be programs which
are already compensating for the problem, so the fix could cause problems
there. Anything which uses the display library should be re-tested.

I removed some of the D_get_?_to_?_[xy]conv() functions, as the factors
were the wrong way around (in the sense that x/y != x*(1/y) when dealing
with floating-point). This only affected d.scale and d.barscale, and
those won't be problematic.

I've changed raster.c and raster_rgb.c to use the pixel's centre rather
than its top-left corner. I also changed d.what.rast to use the same
mechanism, so the results should be consistent; initial experiments
(using a 320x200 display to allow selecting specific pixels) confirm
this.

The complete set of files touched by the changes is:

	src/display/d.barscale/cmd/draw_scale.c
	src/display/d.scale/cmd/draw_scale.c
	src/display/d.what.rast/cmd/what.c
	src/include/display.h
	src/libes/display/cnversions.c
	src/libes/display/raster.c
	src/libes/display/raster_rgb.c

-- 
Glynn Clements <glynn.clements@virgin.net>


Tue, Mar 26 2002 17:46:57    Status changed to resolved by gclements  
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