Your server does not support the GD function required to process this type of image.

This is how I’v solved this issue, in a loop….

FROM

$this->load->library('image_lib', $resize_config);
if ( ! $this->image_lib->resize() )
{
    echo $this->image_lib->display_errors();
    exit();
}
$this->image_lib->clear();

TO

$this->load->library('image_lib');
$this->image_lib->initialize($resize_config);
if ( ! $this->image_lib->resize() )
{
    echo $this->image_lib->display_errors();
    exit();
}
$this->image_lib->clear();