local mode=app.params.mode
local out
if mode=='surly_pilot' then
 out=Sprite(192,256,ColorMode.RGB)
 for row,name in ipairs({'south','west','east','north'}) do
  local src=app.open('art/sprites/surly_'..name..'_pilot_v8.png')
  out.cels[1].image:drawImage(src.cels[1].image,Point(0,(row-1)*64));src:close()
 end
elseif mode=='fiddler_run' then
 local src=app.open('art/sprites/fiddler_run_v2.png')
 local image=Image(src.cels[1].image);src:close()
 out=Sprite(192,256,ColorMode.RGB);out.cels[1].image=image
 for _,row in ipairs({0,3}) do
  local name=row==0 and 'south' or 'north'
  local src=app.open('art/sprites/fiddler_run_'..name..'_keys_v3.png')
  local replacement=Image(src.cels[1].image);src:close()
  for y=0,63 do for x=0,191 do image:drawPixel(x,row*64+y,replacement:getPixel(x,y)) end end
 end
 -- The generated front contact repeats the leading leg. Swap only the
 -- lower-leg pixels of the opposite half-cycle; no head/equipment patches.
 for col=2,3 do
  for y=45,63 do for x=15,32 do
   image:drawPixel(col*48+x,y,image:getPixel((col-2)*48+47-x,y))
  end end
 end
 out.cels[1].image=image
end
out:saveAs(app.params.output);out:close()