#!/usr/bin/env bash

# Based on Charles Cooke's 16-color Mandelbrot
# http://earth.gkhs.net/ccooke/shell.html
#    for((P=10**8,Q=P/100,X=320*Q/(`tput cols`-1),Y=210*Q/`tput lines`,
#    y=-105*Q,v=-220*Q,x=v;y<105*Q;x=v,y+=Y));do for((;x<P;a=b=i=k=c=0,
#    x+=X));do for((;a*a+b*b<4*P*P&&i++<99;a=((c=a)*a-b*b)/P+x,b=2*c*b/P+y));
#    do :;done;(((j=(i<99?i%16:0)+30)>37?k=1,j-=8:0));echo -ne "\E[$k;$j"mE;
#    done;echo -e \\E[0m;done # Charles Cooke

trap 'tput sgr0; echo' EXIT
((cols=$(tput cols)-1, lines=$(tput lines)-1))
outside=99
for ((P=10**8,Q=P/100,X=320*Q/cols,Y=210*Q/lines,y=-105*Q,v=-220*Q,x=v; y<105*Q; x=v,y+=Y)); do
	for (( ; x<P; a=b=i=c=0,x+=X)); do
		for (( ; a**2+b**2<4*P**2&&i++<${outside}; a=((c=a)**2-b**2)/P+x,b=2*c*b/P+y)); do :; done
		gray=$((232+(i<${outside}?i*24/${outside}:0)))
		echo -en "\033[48;5;${gray}m \033[0m"
	done
	echo
done

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# vim:set sr et ts=4 sw=4 ft=sh: // See Vim, :help 'modeline'