Concatenate images

convert -size 20x20 xc:black sep.png

cd images

chmod 600 *

for i in * ; do echo $i; convert "$i" -filter Lanczos -resize 1422x1600 "$i"; done
for i in * ; do cp ../sep.png "${i}_.png" ; done
convert * -background black -gravity Center -append big.png

time gwenview big.png