require "bitmap"

local max_iters = 300
local zoom = 1
local move_x = 0
local move_y = 0
local cx = -0.7
local cy = 0.27015
local w = 800
local h = 600
local bmp = bitmap.of(w, h, color.black, "Julia set")

local function create_julia()
    for x = 0, w - 1 do
        for y = 0, h - 1 do
            local zx = 1.5 * (x - w / 2) / (0.5 * zoom * w) + move_x
            local zy = (y - h / 2) / (0.5 * zoom * h) + move_y
            local i = max_iters
            while zx * zx + zy * zy < 4 and i > 0 do
                local tmp = zx * zx - zy * zy + cx
                zy = 2 * zx * zy + cy
                zx = tmp
                i -= 1
            end
            local c = bitmap.rgbColor(i % 256, i % 256, (i * 8) % 256)
            bmp:set(x, y, c)
        end
    end
end

create_julia()
bmp:view()