Re: [ferret_users] Color error in shading with -gif

[Ansley Manke <ansley.b.manke@xxxxxxxx>]

Hi,
I've looked more into the Ferret source code and I do not see the source of this bug.

Ryo's  solution to use PPL SHASET RESET is a good one when using the same color palette AND color levels for each viewport. That's in fact a common thing to do, so that the colors in each image are the same.

However the user should not have to know that a workaround is needed for a particular kind of graphics, and we're talking about some solutions to this issue, perhaps to not make this special call for doing SHADE plots in -gif mode.

This will not be an issue with PyFerret, which uses different underlying graphics libraries.


Ansley

On 2/15/2013 5:35 AM, Ge Peng - NOAA Affiliate wrote:

Yes, shading plot twice appears to a work-around solution for the problem. 

However, shifting color scales in the same figure with multiple plots can be disconcerting as it affects your analysis results and potentially impacts the scientific outcomes. As the result, I usually have to create each shading figure individually as well to see if there is color scale shift as shading the high-resolution fields twice may not be something one wants to do unless it is necessary.

It would be better if this issue can be dealt with by ferret.

Thanks,

--- Peng

-----------------------------------------------

Ge Peng, Ph.D

Research Scholar

Cooperative Institute for Climate and Satellites

North Caroline State University (CICS-NC)

Remote Sensing and Applications Division/NCDC

151 Patton Ave, suite 410

Asheville, NC 28801-5001

Ge.Peng@xxxxxxxx

Office: (828)257-3009

Fax: (828)271-4328

 

Disclaimer:
The opinions expressed in this email are those of the author. They do not necessarily reflect the official views or policies of NOAA, Department of Commerce, or the US Government.

On Thu, Feb 14, 2013 at 7:24 PM, Ryo Furue <furue@xxxxxxxxxx> wrote:

Hi Bill,

> I've done some more checks on this. I have simplified my scripts down to a
> very simple multi-panel shade plot and the problem persists and appears to
> be the same issue reported back in 2008
> (http://www.pmel.noaa.gov/maillists/tmap/ferret_users/fu_2008/msg00470.html
> ) and again in 2009
> (http://www.pmel.noaa.gov/maillists/tmap/ferret_users/fu_2009/msg00451.html
> ). This is a pretty dangerous bug because the error is not always obvious
> and it would be easy to not catch a one level error if many levels were
> selected. In the 2008 thread the problem was blamed on some axis
> manipulation. However, in my case I can reproduce the problem with just a
> series of basic shade commands (see script below).

You may be interested in the workaround I proposed in 2009:

http://www.pmel.noaa.gov/maillists/tmap/ferret_users/fu_2009/msg00216.html

I've been able to reproduce your problem with your original script,
and I've modified it to the attached one, which solves the problem.

Cheers,
Ryo
--------------
!       use "../test.nc"

use "etopo120.cdf"

set v ul
shade/lev=5 rose

ppl shaset reset  !! <--

set v ur
shade/lev=5 rose

ppl shaset reset  !! <--

set v ll
shade/lev=5 rose

ppl shaset reset  !! <--

set v lr
shade/lev=5 rose
shade/ov/nolab/lev=5 rose

frame/file="test.gif"