[ncl-talk] Can i set the opacity of each color ??

[Rabah Hachelaf]

Hi Kyle,

I think your suggestion doesn't work because when i add the 4th values for
opacity i get this message ;
(0)     Warning: gsn_define_colormap: cmap must either be an n x 3 float
array,
(0)     a single pre-defined colormap name, or a 1-dimensional string array
of named colors.

i simplified my script like this :

colors = (/ (/255,255,255,1/), (/163,255,163,125/), (/255,178,102,200/) /)
* 1.0
colors= colors/255.
print(colors)

gsn_define_colormap(wks,colors)
......
......
.........
res at cnLevelSelectionMode = "ExplicitLevels"     ; set explicit contour
levels
res at cnLevels    = (/ 40,70,100/) ; set levels
res at cnFillColors = (/ 0,1,2/)





2014-08-28 22:42 GMT-04:00 Kyle Griffin <ksgriffin2 at wisc.edu>:

> You should be able to just add a fourth value to your RGB triplets to make
> them RGBA (A for alpha) quadruplets. Since you already divide the numbers
> out of 255, you can simply add the alpha on the same scale, with 0 =
> transparent and 1=opaque (or 255, in your case).
>
> More of the problem is that you don't seem to be assigning the color array
> you create at the beginning of the script to the cnFillColors resource you
> set later on. Look at some of the examples on the NCL website discussing
> how to work with the new color capabilities at:
> http://www.ncl.ucar.edu/Applications/rgbacolor.shtml
>
>
> Kyle
>
> ----------------------------------------
> Kyle S. Griffin
> Department of Atmospheric and Oceanic Sciences
> University of Wisconsin - Madison
> Room 1421
> 1225 W Dayton St, Madison, WI 53706
> Email: ksgriffin2 at wisc.edu
>
>
> On Thu, Aug 28, 2014 at 8:44 PM, Rabah Hachelaf <hachelaf at sca.uqam.ca>
> wrote:
>
>>
>> Hi all ,
>>
>> I am using the script below to plot humidity between 40-70%(green) and
>> 70-100% (orange).
>>
>> I want to know if i can set the opacity for each color for example
>> opacity 50% for the green color and 100% for the orange.
>>
>> Thanks for help.
>>
>> ;************************************************
>> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
>> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
>> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
>> ;************************************************
>> begin
>>  a = addfile("gfs.t00z.pgrb2f00.grib2","r")
>>     lon = a->lon_0
>>     lat = a->lat_0
>>     icing     = short2flt(a->RH_P0_L100_GLL0({50000},:,:))
>>
>> print(icing(1:4,1:4))
>> ;********************************************************
>> ;  Display parameters
>> ;***************************************
>> zoom="test"
>> pixel=2048
>> ;***************************************************
>>
>> wks_type="png"
>>
>>   wks_type at wkWidth = pixel
>>    wks_type at wkHeight = pixel
>>   wks_type at wkBackgroundOpacityF = 0.0
>> wks = gsn_open_wks(wks_type,"icing_test")
>>
>> colors = (/ (/255,255,255/),(/0,0,0/),(/255,255,255/), (/244,255,244/), \
>>               (/217,255,217/), (/163,255,163/), (/106,255,106/), \
>>               (/43,255,106/), (/0,224,0/), (/0,134,0/),(/255,145,0/),\
>>               (/255,178,102/) /) * 1.0 ; we multiply by 1 to make colors
>> float
>>
>> colors = colors/255.
>>
>>
>> gsn_define_colormap(wks,colors)
>>
>>
>> res                   = True
>>   res at mpProjection      = "Mercator"       ; choose projection
>>   res at mpGridAndLimbOn   = False             ; turn on lat/lon lines
>>   res at mpPerimOn         = False             ; turn off box around plot
>>   res at mpFillOn          = False
>>   res at mpOutlineOn       = True
>>   res at cnFillOn          = True              ; color plot desired
>>   res at cnLineLabelsOn    = False             ; turn off contour lines
>>    res at mpLimitMode  = "LatLon"
>>    res at mpMinLatF            =   -85.0
>>     res at mpMaxLatF            =  85.0
>>     res at mpMinLonF            = -180
>>     res at mpMaxLonF            = 180
>>   res at vpXF            = 0                 ; make plot bigger
>>   res at vpYF            = 1
>>   res at vpWidthF        = 1
>>   res at vpHeightF       = 1
>>
>> res at cnLevelSelectionMode = "ExplicitLevels"    ; set explicit contour
>> levels
>> res at cnLevels    = (/ 40,70,100/) ; set levels
>> res at cnFillColors = (/ -1,5,11/)
>>
>> ;res at cnFillOpacityF=0.5
>>
>> contour0 = gsn_csm_contour_map(wks,icing,res)  ; create the plot
>> --
>> ------------------------------
>> Cordialement,
>> Best regards,
>> Rabah Hachelaf
>>
>>
>>
>>
>>
>>
>> --
>> ------------------------------
>> Cordialement,
>> Best regards,
>> Rabah Hachelaf
>>
>> _______________________________________________
>> ncl-talk mailing list
>> List instructions, subscriber options, unsubscribe:
>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>
>>
>


-- 
------------------------------
Cordialement,
Best regards,
Rabah Hachelaf
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.ucar.edu/pipermail/ncl-talk/attachments/20140828/f551d31f/attachment.html