Generating color palette for Xmgrace

We provide some simple scripts that generates colormap for Xmgrace. Just copy paste the output in your grace file.

grayscale colormap

<source lang="py">

</source>

HSV colormap

Use RGB to HSV and reciprocal conversion. Gradients are much easier to derive in HSV format. One can use 'sin' functions instead of linear ones.

<source lang="py">

1. !/usr/bin/python

print "@map color 0 to (255, 255, 255), \"white\"" print "@map color 1 to (0, 0, 0), \"black\""

def RGBtoHSV( (R,G,B) , fac = 255.0 ):

   R /= fac
   G /= fac
   B /= fac
   M = max(R,G,B)
   m = min(R,G,B)
   C = M-m
   Hp = 0
   if not C==0:

if M==R: Hp = ((G-B)/C)%6 elif M==G: Hp = (B-R)/C + 2 elif M==B: Hp = (R-G)/C + 4

   H = Hp*60
   V = M
   S = C/V
   return (H,S,V)

def HSVtoRGB( (H,S,V) ):

   C = V*S
   Hp = H/60
   X = C*(1-abs(Hp%2-1))
   (R1,G1,B1) = (0,0,0)
   if   0<=Hp and Hp<1: (R1,G1,B1) = (C,X,0)
   elif 1<=Hp and Hp<2: (R1,G1,B1) = (X,C,0)
   elif 2<=Hp and Hp<3: (R1,G1,B1) = (0,C,X)
   elif 3<=Hp and Hp<4: (R1,G1,B1) = (0,X,C)
   elif 4<=Hp and Hp<5: (R1,G1,B1) = (X,0,C)
   elif 5<=Hp and Hp<6: (R1,G1,B1) = (C,0,X)
   m = V-C
   (R,G,B) = (R1+m,G1+m,B1+m)
   return (int(255*R),int(255*G),int(255*B))

def HSVGradient(start,stop,num):

   N=int(256/(num-1))
   (h1,s1,v1) = start
   (h2,s2,v2) = stop
   (hs,ss,vs) = ((h2-h1)/float(num-1),(s2-s1)/float(num-1),(v2-v1)/float(num-1))
   for i in range(num):

(h,s,v) = (h1+i*hs,s1+i*ss,v1+i*vs) (r,g,b) = HSVtoRGB( (h,s,v) ) print "@map color "+str(i+2)+" to "+str((r,g,b))+", \"grad"+str(i+1)+"\""

rgbred, rgbgreen, rgbblue = (255,0,0), (0,255,0), (0,0,255) hsvred, hsvgreen, hsvblue = RGBtoHSV(rgbred), RGBtoHSV(rgbgreen), RGBtoHSV(rgbblue)

HSVGradient(hsvred,hsvblue,11)

1. HSVGradient((0.0,1.0,1.0),(240.0,1.0,1.0),24)

</source>