undefined function imagecreatefromjpeg() in class-wo-worldmap.php

Hello, I am getting the following errors (a plenty of):

2015/03/12 13:25:56 [error] 23106#0: *783829 FastCGI sent in stderr: "PHP message: PHP Fatal error: Call to undefined function imagecreatefromjpeg() in /var/www/mysite/wp-content/plugins/visitor-maps/class-wo-worldmap.php on line 187" while reading response header from upstream, client: IP HERE, server: mysite.com, request: "GET /?do_wo_map=1&time=15&units=minutes&map=2&pin=1&pins=off&text=on&textcolor=000000&textshadow=FFFFFF&textalign=cb&ul_lat=0&ul_lon=0&lr_lat=360&lr_lon=180&offset_x=0&offset_y=0&wp-minify-off=1&type=png HTTP/1.1", upstream: "fastcgi://*****", host: "mysite.com", referrer: "https://mysite.com/wp-admin/index.php?page=visitor-maps"

please help, thanks in advance

https://wordpress.org/plugins/visitor-maps/