lua-xpm: test_mandelbrot.lua

-- Code originally by Luiz Henrique de Figueiredo
-- At http://lua-users.org/lists/lua-l/2010-10/msg00754.html
-- Ported to lua-xpm by Matthew Wild
 
local xpm = require "xpm";
 
local N=255
 
local pic = xpm.new(N,N);
 
for i=1,N do
	local y=2-4*(i-1)/(N-1)
	for j=1,N do
		local x=-2+4*(j-1)/(N-1)
		local xc,yc=x,y
		local X,Y=0,0
		local p=0
		for n=1,255 do
			X,Y = X^2-Y^2+xc, 2*X*Y+yc
			if X^2+Y^2>4 then p=n break end
		end
		pic:setpixel(j, i, ("#%02x%02x%02x"):format(p,p,p));
	end
end
 
pic:render(io.stdout);

1	-- Code originally by Luiz Henrique de Figueiredo
2	-- At http://lua-users.org/lists/lua-l/2010-10/msg00754.html
3	-- Ported to lua-xpm by Matthew Wild
4
5	local xpm = require "xpm";
6
7	local N=255
8
9	local pic = xpm.new(N,N);
10
11	for i=1,N do
12	local y=2-4*(i-1)/(N-1)
13	for j=1,N do
14	local x=-2+4*(j-1)/(N-1)
15	local xc,yc=x,y
16	local X,Y=0,0
17	local p=0
18	for n=1,255 do
19	X,Y = X^2-Y^2+xc, 2XY+yc
20	if X^2+Y^2>4 then p=n break end
21	end
22	pic:setpixel(j, i, ("#%02x%02x%02x"):format(p,p,p));
23	end
24	end
25
26	pic:render(io.stdout);