Takes a source gif, an overlay image, and a transformed texture square to render under the overlay image. Position animated GIF inside image

mask_gif_onto_image.sh

FILTER="
	[0:v] scale=512:512[src];
	[2:v]format=rgba64,colorchannelmixer=rr=1/128:bb=1/128[map16];
	[map16]extractplanes=r+b+a[x][y][a];
	[src][x][y]remap[remap];
	[remap][a]alphamerge[remapa];
	[remapa][1:v]overlay"
echo "===="
echo $FILTER
echo "===="
GIF=$1
OVERLAY=$2
MASK=$3
OUT=$4
ffmpeg -i $GIF -i $OVERLAY -loop 1 -i $MASK \
-filter_complex "${FILTER}" \
-pix_fmt yuv420p \
$OUT