Particle generator

-- In storyboard scene function
-- group is self.view

-- Colorspace changing function
local function HSVtoRGB(h, s, v)
    local r,g,b
    local i
    local f,p,q,t
    if s == 0 then
        r  = v
        g = v
        b = v
        return math.round(r * 255), math.round(g * 255), math.round(b * 255)
    end
    h =   h / 60;
    i  = math.floor(h);
    f = h - i;
    p = v *  (1 - s);
    q = v * (1 - s * f);
    t = v * (1 - s * (1 - f));
    if i == 0 then
        r = v
        g = t
        b = p
    elseif i == 1 then
        r = q
        g = v
        b = p
    elseif i == 2 then
        r = p
        g = v
        b = t
    elseif i == 3 then
        r = p
        g = q
        b = v
    elseif i == 4 then
        r = t
        g = p
        b = v
    elseif i == 5 then
        r = v
        g = p
        b = q
    end
    return math.round(r * 255), math.round(g * 255), math.round(b * 255)
end


-- Particle generation
local mRandom = math.random
local function newExplosion(params)
    local gr, x, y = params.g, params.x, params.y
    local star, r, g, b
    local s = 1
    if params.big then
        s = 4
    end
    for i = 1, mRandom(5 * s, 15 * s) do
        star = display.newRect(gr, x - 8, y - 4, 8, 8)
        r, g, b = HSVtoRGB(mRandom(1, 359), 1, 1)
        star:setFillColor(r, g, b)
        star.blendMode = 'add'
        transition.to(star, {time = mRandom(100, 500), x = mRandom(-30 * s, 30 * s), y = mRandom(-50 * s, 50 * s), alpha = -1, delta = true, onComplete = function (target) display.remove(target) end})
    end
end

newExplosion{g = group, x = 160, y = 240}