[mapserver-users] color attribute question

[Carlos Ruiz]

To achieve more flexibility as you want, you have to code a function with PL/pgSQL in PostgreSQL or with PHP/Python/Java/C# with Mapscript to define which is the base color (red, green, blue, yellow ...) and then to calculate the percent in the right RGB channel.


Cheers

Mtro. Carlos Ruiz

--------------------------------------------
On Mon, 6/23/14, Do Wi <dowi84 at gmail.com> wrote:

 Subject: Re: [mapserver-users] color attribute question
 To: "Carlos Ruiz" <boolean10001 at yahoo.com>
 Date: Monday, June 23, 2014, 2:56 PM
 
 thanks allot!
 Steve and another user here mentioned this path
 and it did work!only problem is that it cannot be
 changed later if for example the user chooses a blue
 gradient.
 
 how will i go about doing it with
 mapscript?
 maybe it relates to my question herehttp://gis.stackexchange.com/questions/102862/when-to-choose-mapscript-over-mapfile-or-vice-versa
 
 
 :-)
 thanks allot!dovi
 
 On Mon, Jun 23, 2014
 at 6:13 PM, Carlos Ruiz <boolean10001 at yahoo.com>
 wrote:
 
 
 Do,
 If
 you want to do this without using mapscript, you can pull
 the gradient calculation as an attribute from your data
 table.
 
 
 ALTER TABLE mytable ADD COLUMN gradient_color
 VARCHAR;
 UPTATE mytable SET gradient_color = floor(gradient *
 255)::text || ' 0 0';
 
 Cheers
 
  Mtro. Carlos Ruiz
 
  
    
 On Monday, June 23, 2014 4:59 PM, "Lime, Steve D
 (MNIT)" <Steve.Lime at state.mn.us>
 wrote:
 
     
 
  
 
 You can compute a color
 string using PostgreSQL string functions: 
    
   SELECT percentage ||
 ‘ 0 0’ AS color FROM … 
    
 Steve 
    
 From: mapserver-users-bounces at lists.osgeo.org
 [mailto:mapserver-users-bounces at lists.osgeo.org]
 On Behalf Of Do Wi
 
 Sent: Sunday, June 22, 2014 3:50 PM
 
 To: mapserver-users at lists.osgeo.org
 
 Subject: [mapserver-users] color attribute
 question 
    
 
 hi! 
 
    
 
 
 i have this
 scenario: 
 
 
 i have a column in my
 postgis table which contains a double representing a
 percentage. 
 
 
    
 
 
 i want to color my
 polygons in a gradient fashion based on that
 number. 
 
 
    
 
 
 the docs states three
 ways to specify color: 
 
 
 1. three [1-255]
 numbers 
 
 
 2. hex
 string 
 
 
 3.
 [attribute] 
 
 
    
 
 
 but the attribute must
 be a string by itself in the same format as options 1 or
 2. 
 
 
    
 
 
 how can i achieve
 something like  
 
 
    
 
 
 COLOR [percentage]*255 0
 0 
 
 
 or 
 
 
 COLOR [percentage] 0
 0 
 
 
 if percentageis already
 0..255 
 
 
    
 
 
 for a red gradient for
 example?  
 
 
    
 
 
 thanks
 allot! 
 
 
 
 
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