#!/usr/bin/env python
# v1.1 29 December 2007
# Python program for making a julia set in a PPM file.
# This version will be SLOW. It does not use numerical arrays. 
# Here is what the program does.  For every (x,y) point within
# a rectangular grid, the point is treated as complex number z.
# The following very simple equation is interated for up to
# itermax times:
# z=z^2 +c
# Depending on whether that iteration converges or diverges,
# a color is assigned to the (x,y) point.  By diverge ("breakout"), it is
# meant that |z|^2 becomes greater than the number breakout
# with itermax iterations.
import sys,getopt 
from math import sqrt
from os import system 
#import psyco #not useful, did not increase speed
#psyco.full()
###############
#default arguments:
filename="frompython.ppm"
h=400 
w=600 
magnify=10
itermax=100
breakout=64.
cr=-.7492
ci=.1
x0=.09950
y0=-.00062
displayppm=False
#change default from commandline
(options,arguments)=getopt.getopt(sys.argv[1:],'h:w:b:m:i:d',["cr=","ci=","x0","y0="])
for op,ar in options:
	if op=="--cr": cr=float(ar)
	if op=="--ci": ci=float(ar)
	if op=="--x0": ci=float(ar)
	if op=="--y0": ci=float(ar)
	if op=="-m": magnify=float(ar)
	if op=="-i": itermax=int(ar)
	if op=="-h": h=int(ar)
	if op=="-w": w=int(ar)
	if op=="-b": breakout=float(ar)
	if op=="-d": displayppm=True
rb=sqrt(breakout)
# header for ppm file
pfile=open(filename,'wb')
pfile.write("P6\n") 
pfile.write("#magnify=%f itermax=%d\n" % (magnify, itermax)) 
pfile.write("%d %d\n" % (w, h)) 
pfile.write("255\n")
#loop over all pixels 
for j in range(1,h+1):
	for i in range(1,w+1):
		x=4*(1.*i/w - .5)/magnify+x0
		y=(4.*h/w)*(1.*(h+1-j)/h - .5)/magnify+y0
		zm=0
		iter=0
		while iter < itermax: 
			xl=x
			yl=y
			xx=x*x - y*y + cr;
			y=2*x*y + ci
			x=xx
			zsq=x*x+y*y
			if zsq>zm: zm=zsq
			if zsq>breakout: break
			iter=iter+1
		if iter>=itermax :
			red=0
			green=int(255.*zm/breakout) 
			blue=int(255.*zm/breakout) 
		else:
			red=int(255.*(rb+xl)/(2*rb))
			green=0
			blue=int(.5*255.*(rb+yl)/(2*rb))
		pfile.write("%c%c%c" % (red,green,blue))
	print "processed row",j,"of",h
pfile.close()
print "wrote ",w,"by",h, "ppm file: ",filename 
if displayppm: system("display "+filename)