I made a small revision; now each single bar is not a resized frame, but its average color; result is really similar, but now it's "smoother", and, when saved as image, takes a lot see space.
Code:
function MovieBarCode2(clip clip, int "w", int "h")
{
GScript("""
w=default(w,1280) h=default(h,480)
clip.ConvertToYV24
src = mt_lutf(last, mode="avg", expr="x", u=3, v=3)
comp = src.BlankClip(width=1, height=h)
for(f=1,w,1)
{
fc = src.framecount
cf = (fc / w) * f
s = src.SelectEvery(fc, cf).PointResize(1, h)
comp = StackHorizontal(comp, s)
}
return comp.Crop(1, 0, 0, 0).Trim(0,-1)
""")
}