jpg_transform.lua

require "gd"

function project(px, py, pz, win_width, win_height, fov, cam)
    local factor = fov / (cam+pz)
    local x = px*factor + win_width/2
    local y = -py*factor + win_height/2
    return x, y
end

local base = gd.createFromJpeg("base.jpg")
local basepal = base:createPaletteFromTrueColor(true, 150)
local black = basepal:colorAllocate(0, 0, 0)
local sizex, sizey = base:sizeXY()
local colors = {}
for x = 1, sizex do
    colors[x] = {}
    for y = 1, sizey do
        local color = base:getPixel(x, y)
        local colorpal = basepal:getPixel(x, y)
        colors[x][y] = {
            r = base:red(color),
            g = base:green(color),
            b = base:blue(color),
            p = colorpal}
        local c = colors[x][y]
        c.w = (c.r+c.g+c.b)/3
    end
end
local xo = {}
for x = 1, sizex/2 do table.insert(xo, x) end
for x = sizex, sizex/2, -1 do table.insert(xo, x) end
basepal:gifAnimBegin("out.gif", true, 0)
for frm = 0, 29 do
    local prev = basepal
    basepal:filledRectangle(0, 0, sizex, sizey, black)
    for _, x in pairs(xo) do
        for y = 1, sizey do
            local px, py = project(x-sizex/2, -y+sizey/2,
                -frm*math.pow(math.max(0, colors[x][y].w-20)/200, 3), sizex, sizey, 30, 30)
            basepal:setPixel(px, py, colors[x][y].p)
        end
    end
    basepal:gifAnimAdd("out.gif", false, 0, 0, 5, gd.DISPOSAL_NONE, prev)
    --gd.DISPOSAL_RESTORE_BACKGROUND)
    print("frame", frm)
end
gd.gifAnimEnd("out.gif")
os.execute("out.gif")