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Brian, I spent the day digging into the guts of the VisAD API. I made some progress, but never really got to the bottom of the problem. I contacted the folks at SSEC about the issue. That's where I am at. Hopefully, we'll hear back from them shortly. Best, Unidata IDV Support > Thanks! > > Yes, if a contour is a line of constant value, then its color should be > constant. > > That is pure logic, although the numerics of the approximations are > understandable. > > Interesting how subtle visad contour segments are. > > Brian Mapes > This message was typed on a cell phone, please forgive its terseness and any > errors. > > > On Jan 21, 2016, at 7:24 PM, Unidata IDV Support <address@hidden> wrote: > > > > Brian, > > > > This is what matplotlib does. See attached. > > > > Best, > > > > Unidata IDV Support > > > >> Animated gif with numerous, fat contours is clearer > >> > >> [cid:76F2C985-9C25-4213-B9FB-DB0E76605743@attlocal.net] > >> > >> > >> On Jan 20, 2016, at 10:37 PM, Brian Mapes > >> <address@hidden<mailto:address@hidden>> wrote: > >> > >> Oh, I notice that smoothing was on in the contour display. When I set the > >> countours unsmoothed,there is still some purple (color mixing), but it is > >> all within pixel scale it seems. > >> > >> > >> <PastedGraphic-6.png> > >> > >> <IDVcont.colormixing.gif> > >> > >> > >> > >> > >> On Jan 20, 2016, at 7:31 PM, Unidata IDV Support > >> <address@hidden<mailto:address@hidden>> wrote: > >> > >> Brian, > >> > >> Yes, I don't think it is a problem with the color scale. This may be a > >> subtle > >> contouring artifact where the contouring algorithm is drifting into areas > >> in > >> shouldn't, if you see what I mean. This is something you would never notice > >> except in these two-tone scenarios. (I would continue experimenting with > >> the > >> contouring parameters rather than the color table at this point.) > >> > >> Can you explain to me how you are deriving DTdy? I am curious how other > >> plotting packages handle these data. > >> > >> Best, > >> > >> Unidata IDV Support > >> > >> I wonder if it is a matter of having only 6 colors in the table? > >> > >> No, I made it more (still half red, half blue) using the + in the color > >> table editor, and changed the range, and the contours are still woozy > >> purplish . > >> So it is not some color-interpolation thing I think. > >> > >> > >> > >> On Jan 20, 2016, at 6:44 PM, Unidata IDV Support > >> <address@hidden<mailto:address@hidden>> wrote: > >> > >> Brian, > >> > >> Thinking about this a bit more, I don't believe there is a bug or problem > >> here. > >> > >> The color table is being displayed in exactly the manner you wish. In > >> particular, where you are seeing "blending" are areas where values in the > >> contour data are actually going back and forth across zero and therefore > >> are mixed > >> purple. It is not the colors that are blending, it is the data themselves > >> across > >> the "zero boundary". > >> > >> Another way of looking at this is choosing a two tone black and white color > >> table. The white will fade into the background. You will see grey as the > >> data > >> approach either side of zero. > >> > >> Do you buy this theory? :-) > >> > >> Best, > >> > >> Unidata IDV Support > >> > >> Same issue when I import this new table. > >> Contours are not uniform red or blue, but mixed purple. > >> Thicker contour line width helps show it. > >> > >> [cid:3EC5425C-85EE-4B22-87E4-1F10BC1A1C6C] > >> > >> > >> > >> > >> > >> On Jan 20, 2016, at 3:16 PM, Unidata IDV Support > >> <address@hidden<mailto:address@hidden><mailto:address@hidden>> wrote: > >> > >> Brian, > >> > >> It is not that the colors are bleeding, it is your color table that > >> appears to > >> be discreet, but apparently is not. Remove all other displays and you will > >> see > >> what I mean. I am unfortunately having trouble loading your bundle though > >> I did > >> get it to load once where I was able to come to that conclusion. > >> > >> Try the attached color table which I believe is actually discreet. > >> > >> Best, > >> > >> Unidata IDV Support > >> > >> > >> > >> See how some of the contours are purplish? The color bar is purely > >> blue/red . > >> > >> Is it a bug, or something we have to live with? > >> Small .zidv bundle attached along with screenshot. > >> > >> Brian > >> > >> > >> > >> > >> > >> > >> > >> > >> > >> Ticket Details > >> =================== > >> Ticket ID: WAX-506623 > >> Department: Support IDV > >> Priority: Normal > >> Status: Open > >> > >> > >> = > >> > >> > >> > >> ********************************************* > >> Brian Mapes, Professor > >> Department of Atmospheric Sciences > >> Meteorology and Physical Oceanography Program > >> RSMAS, University of Miami > >> 4600 Rickenbacker Causeway > >> Miami, FL 33149-1098 > >> > >> phone: (305) 421-4275 > >> fax: (305) 421-4696 > >> email: address@hidden<mailto:address@hidden> > >> Web: http://www.rsmas.miami.edu/users/bmapes/ > >> ********************************************** > > > > > > Ticket Details > > =================== > > Ticket ID: WAX-506623 > > Department: Support IDV > > Priority: Normal > > Status: Open > > <temp4.png> > > <temp5.png> > > <matplotlib.txt> > > Ticket Details =================== Ticket ID: WAX-506623 Department: Support IDV Priority: Normal Status: Open