# 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)
```

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))

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)

```

## 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,sfac*hsv,min(1.0,vfac*hsv))
print "@map color "+str(i)+" to "+str(HSVtoRGB(lighter))+", \"light"+name[c]+"\""
i+=1
```