-- Minor native-pixel motion pass on four existing key drawings. Head, torso,
-- limbs and equipment translate together; only the planted sole rolls 1px.
local function numbers(value)
  local out={}
  for n in string.gmatch(value,'[^,]+') do table.insert(out,tonumber(n)) end
  return out
end
local keys=numbers(app.params.keys)
local drops=numbers(app.params.drops)
local weights=numbers(app.params.weights)
local cycle=tonumber(app.params.cycle)
local src=app.open(app.params.source)
local original=Image(src.cels[1].image)
local atlas=Image(#keys*48,256,ColorMode.RGB)
local names={'south','west','east','north'}
for row=0,3 do
  local gif=Sprite(48,64,ColorMode.RGB)
  for index,col in ipairs(keys) do
    local base=Image(48,64,ColorMode.RGB)
    base:drawImage(original,Point(-col*48,-row*64))
    local floor=-1
    for p in base:pixels() do
      if app.pixelColor.rgbaA(p())>0 then floor=math.max(floor,p.y) end
    end
    local frame=Image(48,64,ColorMode.RGB)
    local drop=drops[index]
    frame:drawImage(base,Point(0,drop))
    if drop~=0 then
      -- Keep the authored planted sole on the floor. This changes one boot
      -- edge rather than stretching the shin, neck, or a torso band.
      for y=floor+1,63 do for x=0,47 do frame:putPixel(x,y,0) end end
      for x=0,47 do frame:putPixel(x,floor,base:getPixel(x,floor)) end
    end
    atlas:drawImage(frame,Point((index-1)*48,row*64))
    if index>1 then gif:newFrame() end
    gif.cels[index].image=Image(frame)
    gif.frames[index].duration=cycle*weights[index]/#keys
  end
  app.command.SpriteSize{ui=false,width=144,height=192,method='nearest-neighbor'}
  gif:saveAs(app.params.preview..'_'..names[row+1]..'.gif');gif:close()
end
src:close()
local sheet=Sprite(#keys*48,256,ColorMode.RGB)
sheet.cels[1].image=atlas;sheet:saveAs(app.params.output)
app.command.SpriteSize{ui=false,width=#keys*144,height=768,method='nearest-neighbor'}
sheet:saveAs(app.params.preview..'_sheet_3x.png');sheet:close()
print('Exported eight timed weight phases from four key drawings; soles anchored.')