--::::::::::::::::::::::::::::::::

--::::::::::::::::::::::::::::::::

-- Retourne un kernel de gauss
function getGaussianKernel(radius,sigma)
    local kernel = {}
    local width = 2*radius+1
    local height = width
    local GKF , e = 0 , 0
    --
    for i = 0-radius,radius do
        for j = 0-radius,radius do
            e = math.exp( (-1*((i*i)+(j*j))) / (2*sigma*sigma))
            GKF = GKF + e
            if not(kernel[i+radius]) then kernel[i+radius] = {} end
            kernel[i+radius][j+radius] = e
        end
    end
    --
    for i = 0-radius,radius do
        for j = 0-radius,radius do
            kernel[i+radius][j+radius] = kernel[i+radius][j+radius] / GKF
        end
    end
    return kernel
end

-- Retourne le voisinage d'un pixel
function GetV(p,x,y,r)
    local V = {}
    for i = 0 , r do
        V[i] = {}
        for j = 0 , r  do
            if (x+i >= 0 and y+j >=0 and x+i < p:width() and y+j < p:height()) then V[i][j] = p:pixel(x+i,y+j) end
    end end
    return V
end

-- Determine le facteur de normalisation
local function GetNormalizeFactor(k)
    local p,n = 0 , 0
    for i,line in pairs(k) do
        for j, value in pairs(line) do
            if (value < 0) then n = n + value
            else p = p + value end
        end
    end
    p , n = math.abs(p),math.abs(n)
    return (((p > n) and p) or n)
end

-- Retourne une image flouter
function gaussianBlur(picture,radius,sigma)
    local kernel = getGaussianKernel(radius,sigma)
    local factor = GetNormalizeFactor(kernel)
    local w,h = picture:width(),picture:height()
    local target = Image.createEmpty(w,h)
    for x = 0 , w-1 do
        for y = 0 , h-1 do
            -- On recupere le voisinage du pixel
            local V = GetV(picture,x,y,radius)
            -- On lui applique le noyau de gauss
            for i,v in pairs(V) do
                for j,k in pairs(v) do
                    if k then
                        local c = k:colors()
                        for key,value in pairs(c) do c[key] = math.floor(math.abs(value * kernel[i][j])/factor) end
                        target:pixel(x,y,Color.new(c.r,c.g,c.b))
                    end
                end
            end
        end
    end
    return target
end

local i = Image.load("pic.jpg")
local o = gaussianBlur(i,3,2)

--[[
while true do
    screen:clear()
    screen:blit(0,0,o)
    screen.flip()
    screen.waitVblankStart()
end
]]