#!/bin/bash
mkdir out

for a in *.jpg ; do
    if (( $(identify -format "%w" "$a") > 1200 ))
        then convert "$a" -crop 50%x100% ./out/"${a%.jpg}".jpg
        else cp "$a" ./out
    fi
done

cd out
for b in *-0.jpg ; do
    mv "$b" "./${b%.jpg}"2.jpg
done