cd png
ffmpeg -framerate 60 -i img_%04d.png -vcodec libx264 -pix_fmt yuv420p -vf "scale=trunc(iw/2)*2:trunc(ih/2)*2" -r 60 demo.mp4
ffmpeg -i demo.mp4 -filter_complex "[0:v] fps=30,split [a][b];[a] palettegen [p];[b][p] paletteuse" demo.gif