using imagemagick to append bottom parts of other images to the first one

combine.sh

#!/bin/bash

if [ $# -lt 1 ]; then
    percent=13
    printf "percent missing: using default value "$percent" %% \n"
else
    percent=$1
fi

type=png

SAVEIFS="$IFS"
IFS=$(echo -en "\n\b")

timestamp=$(date '+%Y%m%d%H%M%S%N')
tmpdir=/tmp/img"$timestamp"
prefix="$tmpdir"/img-

mkdir "$tmpdir"

count=0
for image in $(ls -rt *."$type");
do
    count=`expr $count + 1`
    if [ "$count" -eq 1 ];
    then
        first="$image"
        line=$(identify "$first")
        height=$(echo "$line" | sed -n 's/.*\s[0-9]*x\([0-9]*\)\s.*/\1/p')
        width=$(echo "$line" | sed -n 's/.*\s\([0-9]*\)x[0-9]*\s.*/\1/p')
        bottom=$(echo ""$height" * "$percent" / 100" | bc)
    else
        filename=$(printf "%s%.5d" "$prefix" "$count")."$type"
        convert -chop "$width"x"$height"-"$width"-"$bottom" "$image" "$filename"
    fi
done

convert "$first" "$prefix"*."$type" -append output"$timestamp"."$type"

rm -fr "$tmpdir"

IFS="$SAVEIFS"

exit 0