-- Uniform export of one generated four-key direction. Keep complete anatomy.
local src=app.open(app.params.source)
local pixels=Image(src.cels[1].image)
local boxes=dofile(app.params.boxes)
for p in pixels:pixels() do
 local c=p()
 if app.pixelColor.rgbaA(c)<192 then p(0)
 else p(app.pixelColor.rgba(app.pixelColor.rgbaR(c),app.pixelColor.rgbaG(c),app.pixelColor.rgbaB(c),255)) end
end
src:close()
local maxw,maxh=0,0
for _,b in ipairs(boxes) do maxw,maxh=math.max(maxw,b.w),math.max(maxh,b.h) end
local scale=math.min(42/maxw,tonumber(app.params.height)/maxh)
local frames={}
for i,b in ipairs(boxes) do
 local tmp=Sprite(b.w,b.h,ColorMode.RGB)
 tmp.cels[1].image:drawImage(pixels,Point(-b.x,-b.y))
 local w,h=math.floor(b.w*scale+.5),math.floor(b.h*scale+.5)
 app.command.SpriteSize{ui=false,width=w,height=h,method='nearest-neighbor'}
 local frame=Image(48,64,ColorMode.RGB)
 local dx=math.floor(24-(b.head_x or b.w/2)*scale+.5)
 dx=math.max(0,math.min(48-w,dx))
 local flight=(app.params.gait=='run' and i%2==0) and 2 or 0
 frame:drawImage(tmp.cels[1].image,Point(dx,61-h-flight))
 frames[i]=frame
 tmp:close()
end
local out=Sprite(192,64,ColorMode.RGB)
for i,f in ipairs(frames) do out.cels[1].image:drawImage(f,Point((i-1)*48,0)) end
out:saveAs(app.params.output);out:close()