color transition

-- Color transition wrapper
-- Author: atoko
-- Release date: 5/9/2012
-- Version: 1.0.0
--
--
--
--Description:
--      This is a wrapper for changing fill color within a transition
--  Time, delay and easing values are optional
--
--Usage:
-- cTrans = require( "colortransition" ) ;
--
-- cTrans:colorTransition(displayObject, colorFrom, colorTo, [time], [delay], [easing]) ;
-- ex:
--
--  local rect = display.newRect(0,0,250,250) ;
--      local white = {255,255,255}
--  local red = {255,0,0} ;
--
--  cTrans:colorTransition(rect, white, red, 1200) ;


local _M = {}

--Local reference to transition function
_M.callback = transition.to ;


-- function _M:colorTransition( obj, colorFrom, colorTo, time, onComplete, delay, ease )
function _M:colorTransition( obj, colorFrom, colorTo, time, params  )

        local _obj =  obj ;
        local ease = params and params.ease or easing.linear
        local callbackOnComplete = params and params.onComplete or nil --callback functionality added


        local fcolor = colorFrom or {1,1,1} ; -- defaults to white
        local tcolor = colorTo or {0,0,0} ; -- defaults to black
        local t = nil ;
        local p = {} --hold parameters here

        local rDiff = tcolor[1] - fcolor[1] ; --Calculate difference between values

        local gDiff = tcolor[2] - fcolor[2] ;

        local bDiff = tcolor[3] - fcolor[3] ;

                --Set up proxy
        local proxy = {step = 0} ;

        local mt = {
                __index = function(t,k)
                        --print("get") ;
                        return t["step"]
                end,

                __newindex = function (t,k,v)
                        --print("set")
                        --print(t,k,v)
                        if(_obj.setFillColor) then
                                _obj:setFillColor(fcolor[1] + (v*rDiff) ,fcolor[2] + (v*gDiff) ,fcolor[3] + (v*bDiff) )
                                --_obj.rCol = fcolor[1] + (v*rDiff)
                                --_obj.gCol = fcolor[2] + (v*gDiff)
                                --_obj.bCol = fcolor[3] + (v*bDiff)
                        end
                        t["step"] = v ;
                end
        }

        p.time = time or 1000 ; --defaults to 1 second
        p.delay = params and params.delay or 0 ;
        p.transition = ease ;
        p.onComplete = callbackOnComplete; --callback functionality added


        setmetatable(proxy,mt) ;

        p.colorScale = 1 ;

        t = self.callback( proxy, p, 1 )  ;

        return t

end


return _M ;