Generating color palette for Xmgrace

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

grayscale colormap

#!/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)

HSV colormap and Gradients

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.

#!/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)
#HSVGradient((0.0,1.0,1.0),(240.0,1.0,1.0),24)

Lighter colors

useful if you want to fill object and curves with a lighter color:

#!/usr/bin/python   

black = (0,0,0)
red = (255,0,0)
green = (0,255,0)
blue = (0,0,255)
indigo = (114, 33, 188)
magenta = (255, 0, 255)
orange = (255, 165, 0)
green4 = (0, 139, 0)
maroon = (103, 7, 72)
colors = [ red,blue,green,indigo,magenta,orange,green4,maroon ]
name = { red:'red', blue:'blue', green:'green', indigo:'indigo', magenta:'magenta', orange:'orange', green4:'green4', maroon:'maroon' }

vfac=2
sfac=0.08
grey=int(255*(1-sfac))

i=2
print "@map color 0 to (255, 255, 255), \"white\""
print "@map color 1 to (0, 0, 0), \"black\""
for c in colors:
    print "@map color "+str(i)+" to "+str(c)+", \""+name[c]+"\""
    i+=1
print "@map color "+str(i)+" to "+str( (grey,grey,grey) )+", \"grey\""
i+=1
for c in colors:
    hsv = RGBtoHSV(c)
    lighter = (hsv[0],sfac*hsv[1],min(1.0,vfac*hsv[2]))
    print "@map color "+str(i)+" to "+str(HSVtoRGB(lighter))+", \"light"+name[c]+"\""
    i+=1