fronts.lua

require "path"
require "gd"

local chemin1 = path({point(156, 118), point(748, 104)})
local chemin2 = path({point(136, 172), point(737, 166)})
local npaths = 10
local chemins = {}
local x1step = (chemin2[1].x-chemin1[1].x)/(npaths-1)
local x2step = (chemin2[2].x-chemin1[2].x)/(npaths-1)
local y1step = (chemin2[1].y-chemin1[1].y)/(npaths-1)
local y2step = (chemin2[2].y-chemin1[2].y)/(npaths-1)
for n = 1, npaths do
    table.insert(chemins, path({
            point(chemin1[1].x+(n-1)*x1step,
                  chemin1[1].y+(n-1)*y1step),
            point(chemin1[2].x+(n-1)*x2step,
                  chemin1[2].y+(n-1)*y2step)}
        ):subdivide())
end
local canvas = gd.createFromPng("frms/frm_1.png")
local red = canvas:colorResolve(255, 0, 0)
local f = io.open("fronts.txt", "w")
local l1 = 30
local l2 = 30
local cnt = 0
for frm = 10, 180, 5 do --2, 46, 3 do
    cnt = cnt + 1
    local inputpng = gd.createFromPng("diffs/diff_"..frm..".png")
    local pf0 = nil
    for nligne, chemin in ipairs(chemins) do
        local points = {}
        local ppv = {}
        local dppv = {}
        for _, p in chemin:points() do
            local c = inputpng:getPixel(p.x, p.y)
            local r = inputpng:red(c)
            local g = inputpng:green(c)
            local b = inputpng:blue(c)
            local i = (g/3-10)*3
            -- on voit dans cristal_diff.gif que l'intensite
            -- dominante est dans le vert
            table.insert(points, i)
        end
        for i = l1+1, #points-l1 do
            local c = 0
            for j = i-l1, i+l1 do
                c = c+points[j]
            end
            c = c/(2*l1+1)
            if ppv then
                table.insert(ppv, {i, c})
            end
        end
        for i = l2+1, #points-l2 do
            local c1, c2 = 0, 0
            for j = 1, l2 do
                c1 = c1+points[i-j]
                c2 = c2+points[i+j]
            end
            c1, c2 = c1/l2, c2/l2
            table.insert(dppv, {i, c2-c1})
        end
        local avg = 0
        for _, p in ipairs(ppv) do
            avg = avg + p[2]
        end
        avg = avg / #ppv
        local ph = 0
        --nb de points qui sont au dessus de la moyenne
        for _, p in ipairs(ppv) do
            if p[2] < avg then
                ph = ph + 1
            end
        end
        local mind = 1
        for i, p in ipairs(dppv) do
            if p[2] < dppv[mind][2] then
                mind = i
            end
        end
        local pfront = dppv[mind][1]
        local pf = chemin[pfront]
        if pf then
            f:write(cnt.."\t"
                ..math.floor(pf.x).."\t"
                ..math.floor(pf.y).."\n")
            if pf0 then
                canvas:line(pf0.x, pf0.y, pf.x, pf.y,
                    red)
            end
        end
        pf0 = pf
    end
    io.write(frm.."\t")
    if cnt % 8 == 0 then
        io.write("\n")
    end
end
f:close()
canvas:png("fronts.png")
io.write("\n")