Generating color palette for Xmgrace

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

grayscale colormap

<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 LinearGray(num):

   N=int(255/num)
   for i in range(1,num):
       n = str(N*i)
       print "@map color "+str(i+1)+" to ("+n+','+n+','+n+"), \"gray"+str(i)+"\""

LinearGray(12) </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>