function autofix(clip video, int dirty, int clean, bool vertical) {
  video
  dirty=dirty+(dirty<0 ? vertical ? width : height : 0)
  clean=clean+(clean<0 ? vertical ? width : height : 0)
  GScriptClip("
    video=last
    ConvertToRGB()
    clipdirty=vertical ? Crop(dirty,0,1,0) : Crop(0,dirty,0,1)
    clipclean=vertical ? Crop(clean,0,1,0) : Crop(0,clean,0,1)
    BlankClip(clipdirty)
    dr=Int(RGBDifference(ShowRed(clipclean))-RGBDifference(ShowRed(clipdirty)))
    dg=Int(RGBDifference(ShowGreen(clipclean))-RGBDifference(ShowGreen(clipdirty)))
    db=Int(RGBDifference(ShowBlue(clipclean))-RGBDifference(ShowBlue(clipdirty)))
    RGBAdjust(clipdirty,rb=dr,gb=dg,bb=db)
    Overlay(video,last,x=vertical ? dirty : 0,y=vertical ? 0 : dirty)
  ",args="dirty,clean,vertical")
}