added star shape

shape.lua

 require "baka-fx.shape.potato"
 require "baka-fx.shape.circle"
+require "baka-fx.shape.star"
 
 shape =
 {
     potato = potato,
-    circle = circle
+    circle = circle,
+    star = star
 }
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shape/circle.lua

@@ -60,4 +60,4 @@ function circle(radius, keypoints, clockwise)
     end
   
     return str
-  end
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+end
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shape/star.lua

+--[[
+[Description]
+Draws a star with bezier curves.
+
+[Usage]
+star(outradius, inradius)
+star(outradius, inradius, branches)
+star(outradius, inradius, branches, roundness)
+star(outradius, inradius, branches, roundness, clockwise)
+
+[Arguments]
+outradius: outer radius of the star, in pixels
+inradius: inner radius of the star, in pixels (default a function of outradius)
+branches: number of branches, positive integer >= 2 (default 5)
+roundness: roundness of the branches, between 0 and 1 (default 0)
+clockwise: drawing direction, boolean (default false)
+
+[Notes]
+The star is drawn so that it always has a branch pointing straight up.
+This function does not include drawing tags, only vector commands.
+If no inradius is specified and there are 5 or more branches, the inradius
+is set to outradius * sin(pi/2 - 2pi/n) / cos(pi/n) where n is the number
+of branches. This makes it so the edges of the branches are aligned.
+If no inradius is specified and there are less than 5 branches, the inradius
+is set to outradius / 2.
+--]]
+function star(outradius, inradius, branches, roundness, clockwise)
+    roundness = roundness or 0
+    branches = branches or 5
+    branches = branches >= 2 and branches or 5
+  
+    local halfpi = math.pi / 2
+    local mult = clockwise and -1 or 1
+    local alpha = math.pi / branches
+    
+    inradius = inradius or (branches < 5 and outradius / 2
+        or outradius * math.sin(halfpi - 2 * alpha) / math.cos(alpha))
+
+    local inpoints = {}
+    local outpoints = {}
+  
+    for i = 1, branches do
+        local oa = (2*(i-1)) * mult * alpha - halfpi
+        local ia = oa + mult * alpha
+
+        outpoints[i] =
+        {
+            a = oa,
+            x = outradius * math.cos(oa),
+            y = outradius * math.sin(oa)
+        }
+
+        inpoints[i] =
+        {
+            a = ia,
+            x = inradius * math.cos(ia),
+            y = inradius * math.sin(ia)
+        }
+    end
+
+    outpoints[branches+1] = outpoints[1]
+    inpoints[0] = inpoints[branches]
+
+    local str = ""
+
+    -- No roundness => draw straight lines
+    if roundness < 0.001 then
+        str = "m " .. outpoints[1].x .. " " .. outpoints[1].y .. " "
+
+        for i = 1, branches do
+            local ip = inpoints[i]
+            local op = outpoints[i+1]
+
+            str = str .. "l " .. ip.x .. " " .. ip.y .. " "
+                .. "l " .. op.x .. " " .. op.y .. " "
+        end
+
+        return str
+    end
+
+    local b = outradius - inradius * math.cos(alpha)
+    local hi = (b - roundness * (outradius - inradius)) * math.cos(halfpi - 2 * alpha)
+    local ho = roundness * (outradius - inradius) * math.tan(halfpi - 2 * alpha)
+    local beta = halfpi - alpha
+    local l = inradius + (1 - roundness) * (outradius - inradius)
+    
+    for i = 1, branches do
+        local op = outpoints[i]
+
+        local x = l * math.cos(op.a)
+        local y = l * math.sin(op.a)
+        
+        outpoints[i].x = x
+        outpoints[i].y = y
+        outpoints[i].h1 =
+        {
+            x = x + ho * math.cos(op.a - mult * halfpi),
+            y = y + ho * math.sin(op.a - mult * halfpi)
+        }
+        outpoints[i].h2 =
+        {
+            x = x + ho * math.cos(op.a + mult * halfpi),
+            y = y + ho * math.sin(op.a + mult * halfpi)
+        }
+
+        local ip0 = inpoints[i-1]
+        local ip1 = inpoints[i]
+
+        inpoints[i-1].h2 =
+        {
+            x = ip0.x + hi * math.cos(ip0.a + mult * beta),
+            y = ip0.y + hi * math.sin(ip0.a + mult * beta)
+        }
+        inpoints[i].h1 =
+        {
+            x = ip1.x + hi * math.cos(ip1.a - mult * beta),
+            y = ip1.y + hi * math.sin(ip1.a - mult * beta)
+        }
+    end
+
+    inpoints[branches].h2 = inpoints[0].h2
+    inpoints[0].h1 = inpoints[branches].h1
+
+    str = "m " .. outpoints[1].x .. " " .. outpoints[1].y .. " "
+  
+    for i = 1, branches do
+        local op0 = outpoints[i]
+        local op1 = outpoints[i+1]
+        local ip = inpoints[i]
+
+        str = str .. "b " .. op0.h2.x .. " " .. op0.h2.y .. " "
+            .. ip.h1.x .. " " .. ip.h1.y .. " "
+            .. ip.x .. " " .. ip.y .. " "
+            .. "b " .. ip.h2.x .. " " .. ip.h2.y .. " "
+            .. op1.h1.x .. " " .. op1.h1.y .. " "
+            .. op1.x .. " " .. op1.y .. " "
+    end
+  
+    return str
+end
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