Generate thumb for cover.jpg generate by Calibre

thumbnail.sh

#!/bin/bash
find ./ -type f -name cover.jpg | while read -r cover;do
        backup=`echo "$cover" | sed -e 's/cover\.jpg$/cover_bak\.jpg/'`
        thumb=`echo "$cover" | sed -e 's/cover\.jpg$/thumb\.jpg/'`
#        thumb=$(echo "$cover" | rev | cut -d "/" -f 2- | rev)"/thumb.jpg"
        echo "$thumb"
        width=$(identify -format '%w' "$cover")
        if (( width < 350 ));then
                cp "$cover" "$thumb"
        elif (( width >=350 && width < 600 ));then
                convert -resize 50%x50% "$cover" "$thumb"
        else
                convert -thumbnail 300 "$cover" "$thumb"
        fi

        folder=`echo "$cover" | sed -e 's/cover\.jpg$//'`

	mv "$cover" "$backup"
	mv "$thumb" "$cover"

        echo "$folder"
        ls -lh "$folder"
done